testcase

package module
v0.115.0 Latest Latest
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 Go to latest Published: Nov 4, 2022 License: Apache-2.0 Imports: 23 Imported by: 0

README

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testcase

The testcase package provides tooling to apply BDD testing conventions.

Features

  • lightweight, it has no dependency, you just import testcase, no clutter
  • supports classing flattened testing style, table testing style, and nested testing style
    • nested testing style
      • allows the usage of an immutable testing subject
      • nesting visualize code complexity
      • testing context building becomes DRY
      • immutable testing subject construction forces disciplined testing conventions
      • supports also the flattened nesting where testing context branches can to a top-level function
  • DDD based testing composition
    • testing components can be defined and reused across the whole project
    • unit tests can be converted into full-fledged E2E tests for CI/CD pipelines
    • dependency injection during testing becomes a breeze to do
    • reusable testing components increase maintainability aspects
    • reusable testing components decrease required ramp-up time for writing new tests that depend on existing components
  • safe parallel testing
    • variables stored per test execution, which prevents leakage and race conditions across different tests
  • repeatable pseudo-random fixture generation for test input
  • repeatable pseudo-random test order shuffling
    • prevents implicit test dependency on ordering
    • ensures that tests can be added and removed freely without the fear of breaking other tests in the same coverage.
    • flaky tests which depend on test execution order can be noticed at development time

Guide

testcase is a powerful TDD Tooling that requires discipline and understanding of the fundamentals of testing. If you are looking for a guide that helps streamline your knowledge on the topics, then please consider reading the below-listed articles.

Official API Documentation

If you already use the framework, and you just won't pick an example, you can go directly to the API documentation that is kept in godoc format.

Getting Started / Example

Examples kept in godoc format. Every exported functionality aims to have examples provided in the official documentation.

A Basic examples:

func Test_withTestcaseT(t *testing.T) {
	tc := testcase.NewT(t, nil)
	
	tc.Must.True(true)
	_ = tc.Random.String()
}

func Test_withTestcaseSpec(t *testing.T) {
	s := testcase.NewSpec(t)
	
	s.Test("", func(t *testcase.T) {
		t.Must.True(true)
		_ = tc.Random.String()
	})
}

An example with scoped test variables:

package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func TestMyFunc(t *testing.T) {
	s := testcase.NewSpec(t)
	s.NoSideEffect()

	var (
		input = testcase.Let[string](s, nil)
    )
	act := func(t *testcase.T) string {
		return MyFunc(input.Get(t))
	}

	s.When("input is all lowercase", func(s *testcase.Spec) {
		// testing scopes without the input being defined
		// will warn the dev about the missing specification.
		input.LetValue(s, "all lowercase")

		s.Then("it is expected to ...", func(t *testcase.T) {
			t.Must.Equal("all lowercase", act(t))
		})
	})

	s.When("input is all upcase", func(s *testcase.Spec) {
		input.LetValue(s, "ALL UPCASE")

		s.Then("it is expected to ...", func(t *testcase.T) {
			t.Must.Equal("all upcase", act(t))
		})
	})
}

Modules

  • httpspec
    • spec module helps you create HTTP API Specs.
  • fixtures
    • fixtures module helps you create random input values for testing

Summary

DRY

testcase provides a way to express common Arrange, Act sections for the Asserts with a DRY principle in mind.

  • First, you can define your Act section with a method under test as the subject of your test specification
    • The Act section invokes the method under test with the arranged parameters.
  • Then you can build the context of the Act by Arranging the inputs later with humanly explained reasons
    • The Arrange section initializes objects and sets the value of the data that is passed to the method under test.
  • And lastly, you can define the test expected outcome in an Assert section.
    • The Assert section verifies that the action of the method under test behaves as expected.

Then adding test edge case to the testing suite becomes easier, as it will have a concrete place where it must be placed.

And if during the creation of the specification, an edge case turns out to be YAGNI, it can be noted, so visually it will be easier to see what edge case is not specified for the given subject.

The value it gives is that to build a test for a certain edge case, the required mental model size to express the context becomes smaller, as you only have to focus on one Arrange at a time, until you fully build the bigger picture.

It also implicitly visualize the required mental model of your production code by the nesting. You can read more on that in the nesting section.

Modularization

On top of the DRY convention, any time you need to Arrange a common scenario about your projects domain event, you can modularize these setup blocks in a helper function.

This helps the readability of the test while keeping the need for mocks to the minimum as possible for a given test. As a side effect, integration tests can become low-hanging fruit for the project.

e.g.:

package mypkg_test

import (
	"testing"

	"my/project/mypkg"


	"github.com/adamluzsi/testcase"

	. "my/project/testing/pkg"
)

func TestMyTypeMyFunc(t *testing.T) {
	s := testcase.NewSpec(t)
	
	myUser := GivenWeHaveUser(s)
	// .. other givens

	myType := testcase.Let(s, func(t *testcase.T) *mypkg.MyType {
		return &mypkg.MyType{}
	})

	s.Describe(`.MyFunc`, func(s *testcase.Spec) {
		act := func(t *testcase.T) { myType.Get(t).MyFunc(myUser.Get(t)) }

		s.Then(`edge case description`, func(t *testcase.T) {
			act(t)
		})
	})
}

Stability

  • The package is considered stable.
  • The package use rolling release conventions.
  • No breaking change is planned to the package exported API.
  • The package used in production development.
  • The package API is only extended if the practical use case proves its necessity.

Case Study About testcase Package Origin

Reference Project

Documentation

Overview

Package testcase is an opinionated testing framework.

Repository + README: https://github.com/adamluzsi/testcase

Guide: https://github.com/adamluzsi/testcase/blob/master/docs/README.md

Example (AssertEventually) 
package main

import (
	"math/rand"
	"testing"
	"time"

	"github.com/adamluzsi/testcase/assert"
)

func main() {
	waiter := assert.Waiter{
		WaitDuration: time.Millisecond,
		Timeout:      time.Second,
	}
	w := assert.Eventually{RetryStrategy: waiter}

	var t *testing.T
	// will attempt to wait until assertion block passes without a failing testCase result.
	// The maximum time it is willing to wait is equal to the wait timeout duration.
	// If the wait timeout reached, and there was no passing assertion run,
	// the last failed assertion history is replied to the received testing.TB
	//   In this case the failure would be replied to the *testing.T.
	w.Assert(t, func(it assert.It) {
		if rand.Intn(1) == 0 {
			it.Fatal(`boom`)
		}
	})
}

Output:
Example (AssertEventuallyAsContextOption) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/assert"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)

	s.Test(`flaky`, func(t *testcase.T) {
		// flaky test content here
	}, testcase.Flaky(assert.RetryCount(42)))
}

Output:
Example (AssertEventuallyByCount) 
package main

import (
	"math/rand"
	"testing"

	"github.com/adamluzsi/testcase/assert"
)

func main() {
	r := assert.Eventually{RetryStrategy: assert.RetryCount(42)}

	var t *testing.T
	r.Assert(t, func(it assert.It) {
		if rand.Intn(1) == 0 {
			it.Fatal(`boom`)
		}
	})
}

Output:
Example (AssertEventuallyByCustomRetryStrategy) 
package main

import (
	"math/rand"
	"testing"

	"github.com/adamluzsi/testcase/assert"
)

func main() {
	// this approach ideal if you need to deal with asynchronous systems
	// where you know that if a workflow process ended already,
	// there is no point in retrying anymore the assertion.

	while := func(isFailed func() bool) {
		for isFailed() {
			// just retry while assertion is failed
			// could be that assertion will be failed forever.
			// Make sure the assertion is not stuck in a infinite loop.
		}
	}

	r := assert.Eventually{RetryStrategy: assert.RetryStrategyFunc(while)}

	var t *testing.T
	r.Assert(t, func(it assert.It) {
		if rand.Intn(1) == 0 {
			it.Fatal(`boom`)
		}
	})
}

Output:
Example (AssertEventuallyByTimeout) 
package main

import (
	"math/rand"
	"testing"
	"time"

	"github.com/adamluzsi/testcase/assert"
)

func main() {
	r := assert.Eventually{RetryStrategy: assert.Waiter{
		WaitDuration: time.Millisecond,
		Timeout:      time.Second,
	}}

	var t *testing.T
	r.Assert(t, func(it assert.It) {
		if rand.Intn(1) == 0 {
			it.Fatal(`boom`)
		}
	})
}

Output:
Example (AssertEventuallyCount) 
package main

import (
	"github.com/adamluzsi/testcase/assert"
)

func main() {
	_ = assert.Eventually{RetryStrategy: assert.RetryCount(42)}
}

Output:
Example (AssertWaiterWait) 
package main

import (
	"time"

	"github.com/adamluzsi/testcase/assert"
)

func main() {
	w := assert.Waiter{WaitDuration: time.Millisecond}

	w.Wait() // will wait 1 millisecond and attempt to schedule other go routines
}

Output:
Example (AssertWaiterWhile) 
package main

import (
	"math/rand"
	"time"

	"github.com/adamluzsi/testcase/assert"
)

func main() {
	w := assert.Waiter{
		WaitDuration: time.Millisecond,
		Timeout:      time.Second,
	}

	// will attempt to wait until condition returns false.
	// The maximum time it is willing to wait is equal to the wait timeout duration.
	w.While(func() bool {
		return rand.Intn(1) == 0
	})
}

Output:
Example (ClockAfter) 
package main

import (
	"github.com/adamluzsi/testcase/clock"
	"github.com/adamluzsi/testcase/clock/timecop"
	"testing"
	"time"
)

func main() {
	var tb testing.TB
	timecop.SetSpeed(tb, 5)    // 5x time speed
	<-clock.After(time.Second) // but only wait 1/5 of the time
}

Output:
Example (ClockSleep) 
package main

import (
	"github.com/adamluzsi/testcase/clock"
	"github.com/adamluzsi/testcase/clock/timecop"
	"testing"
	"time"
)

func main() {
	var tb testing.TB
	clock.Sleep(time.Second) // normal 1 sec sleep
	timecop.SetSpeed(tb, 5)  // 5x time speed
	clock.Sleep(time.Second) // but only sleeps 1/5 of the time
}

Output:
Example (ClockTimeNow_withTimecop) 
package main

import (
	"github.com/adamluzsi/testcase/clock"
	"github.com/adamluzsi/testcase/clock/timecop"
	"testing"
	"time"

	"github.com/adamluzsi/testcase/assert"
)

func main() {
	var tb testing.TB

	type Entity struct {
		CreatedAt time.Time
	}

	MyFunc := func() Entity {
		return Entity{
			CreatedAt: clock.TimeNow(),
		}
	}

	expected := Entity{
		CreatedAt: clock.TimeNow(),
	}

	timecop.Travel(tb, expected.CreatedAt, timecop.Freeze())

	assert.Equal(tb, expected, MyFunc())
}

Output:
Example (ClockTimeNow_withTravelByDate) 
package main

import (
	"github.com/adamluzsi/testcase/clock"
	"github.com/adamluzsi/testcase/clock/timecop"
	"testing"
	"time"
)

func main() {
	var tb testing.TB

	date := time.Date(2022, 01, 01, 12, 0, 0, 0, time.Local)
	timecop.Travel(tb, date, timecop.Freeze()) // freeze the time until it is read
	time.Sleep(time.Second)
	_ = clock.TimeNow() // equals with date
}

Output:
Example (ClockTimeNow_withTravelByDuration) 
package main

import (
	"github.com/adamluzsi/testcase/clock"
	"github.com/adamluzsi/testcase/clock/timecop"
	"testing"
	"time"
)

func main() {
	var tb testing.TB

	_ = clock.TimeNow() // now
	timecop.Travel(tb, time.Hour)
	_ = clock.TimeNow() // now + 1 hour
}

Output:
Example (FaultInject) 
package main

import (
	"context"
	"errors"
	"fmt"

	"github.com/adamluzsi/testcase/faultinject"
)

func main() {
	defer faultinject.Enable()()

	ctx := context.Background()

	// all fault field is optional.
	// in case left as zero value,
	// it will match every caller context,
	// and returns on the first .Err() / .Value(faultinject.Fault{})
	ctx = faultinject.Inject(ctx, faultinject.CallerFault{
		Package:  "targetpkg",
		Receiver: "*myreceiver",
		Function: "myfunction",
	}, errors.New("boom"))

	// from and after call stack reached: targetpkg.(*myreceiver).myfunction
	if err := ctx.Err(); err != nil {
		fmt.Println(err) // in the position defined by the Fault, it will yield an error
	}
}

Output:

Index

Examples

Constants

View Source 
const (
	OrderingAsDefined testOrderingMod = `defined`
	OrderingAsRandom  testOrderingMod = `random`
)
View Source 
const EnvKeyOrdering = `TESTCASE_ORDERING`

EnvKeyOrdering is the environment variable key that will be checked for testCase determine what order of execution should be used between test cases in a testing group. The default sorting behavior is pseudo random based on an the seed.

Mods: - defined: execute testCase in the order which they are being defined - random: pseudo random based ordering between tests.

View Source 
const EnvKeySeed = `TESTCASE_SEED`

EnvKeySeed is the environment variable key that will be checked for a pseudo random seed, which will be used to randomize the order of executions between test cases.

Variables

View Source 
var DefaultEventually = assert.Eventually{RetryStrategy: assert.Waiter{Timeout: 3 * time.Second}}

Functions

func Append added in v0.39.0 

func Append[V any](t *T, v Var[V], x ...interface{})

Append will append a value[T] to a current value of Var[[]T]. Append only possible if the value type of Var is a slice type of T.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)

	list := testcase.Let(s, func(t *testcase.T) interface{} {
		return []int{}
	})

	s.Before(func(t *testcase.T) {
		t.Log(`some context where a value is expected in the testcase.Var[[]T] variable`)
		testcase.Append(t, list, 42)
	})

	s.Test(``, func(t *testcase.T) {
		t.Log(`list will include the appended value`)
		list.Get(t) // []int{42}
	})
}

Output:

func Race added in v0.40.0 

func Race(fn1, fn2 func(), more ...func())

Race is a test helper that allows you to create a race situation easily. Race will execute each provided anonymous lambda function in a different goroutine, and make sure they are scheduled at the same time.

This is useful when you work on a component that requires thread-safety. By using the Race helper, you can write an example use of your component, and run the testing suite with `go test -race`. The race detector then should be able to notice issues with your implementation.

Example 
package main

import (
	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/internal/example/mydomain"
)

func main() {
	v := mydomain.MyUseCase{}

	// running `go test` with the `-race` flag should help you detect unsafe implementations.
	// each block run at the same time in a race situation
	testcase.Race(func() {
		v.ThreadSafeCall()
	}, func() {
		v.ThreadSafeCall()
	})
}

Output:

func RetryCount added in v0.26.0 

func RetryCount(times int) assert.RetryStrategy

RetryCount is moved from this package.

DEPRECATED: use assert.RetryCount instead

func RunOpenSuite added in v0.79.0 

func RunOpenSuite[TBS anyTBOrSpec](tb TBS, contracts ...OpenSuite)

func RunSuite added in v0.79.0 

func RunSuite[TBS anyTBOrSpec](tb TBS, contracts ...Suite)

RunSuite is a helper function that makes execution one or many Suite easy. By using RunSuite, you don't have to distinguish between testing or benchmark execution mod. It supports *testing.T, *testing.B, *testcase.T, *testcase.Spec and CustomTB test runners.

func Sandbox added in v0.93.0 

func Sandbox(fn func()) sandbox.RunOutcome
Example 
package main

import (
	"fmt"

	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/internal/doubles"
)

func main() {
	stb := &doubles.TB{}
	outcome := testcase.Sandbox(func() {
		// some test helper function calls fatal, which cause runtime.Goexit after marking the test failed.
		stb.FailNow()
	})

	fmt.Println("The sandbox run has finished without an issue", outcome.OK)
	fmt.Println("runtime.Goexit was called:", outcome.Goexit)
	fmt.Println("panic value:", outcome.PanicValue)
}

Output:

func SetEnv added in v0.25.0 

func SetEnv(tb testing.TB, key, value string)

SetEnv will set the os environment variable for the current program to a given value, and prepares a cleanup function to restore the original state of the environment variable.

Spec using this helper should be flagged with Spec.HasSideEffect or Spec.Sequential.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	testcase.SetEnv(tb, `MY_KEY`, `myvalue`)
	// env will be restored after the test
}

Output:

func TableTest added in v0.104.0 

func TableTest[TBS anyTBOrSpec, TC sBlock | tBlock | any, Act tBlock | sBlock | func(*T, TC)](
	tbs TBS,
	tcs map[string]TC,
	act Act,
)

TableTest allows you to make table tests, without the need to use a boilerplate. It optionally allows to use a Spec instead of a testing.TB, and then the table tests will inherit the Spec context. It guards against mistakes such as using for+t.Run+t.Parallel without variable shadowing. TableTest allows a variety of use, please check examples for further information on that.

Example (ActAsCommonSpecContext) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)

	var in = testcase.Let[int](s, nil)
	testcase.TableTest(s, map[string]func(t *testcase.T){
		"when 42": func(t *testcase.T) {
			in.Set(t, 42)
		},
		"whe 24": func(t *testcase.T) {
			in.Set(t, 24)
		},
	}, func(s *testcase.Spec) {
		// common test assertions which applies to all table test scenario
		// it can express "OR" relationship where every testing branch has the same assertions.

		s.Then("", func(t *testcase.T) {
			_ = in.Get(t)
		})

		s.Then("", func(t *testcase.T) {
			_ = in.Get(t)
		})
	})
}

Output:
Example (ClassicInlined) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	myFunc := func(in int) string {
		if in != 42 {
			return "Not the Answer"
		}
		return "The Answer"
	}
	var t *testing.T
	type TTCase struct {
		In       int
		Expected string
	}
	testcase.TableTest(t, map[string]TTCase{
		"when A": {
			In:       42,
			Expected: "The Answer",
		},
		"when B": {
			In:       24,
			Expected: "Not the Answer",
		},
		"when C": {
			In:       128,
			Expected: "Not the Answer",
		},
	}, func(t *testcase.T, tc TTCase) {
		got := myFunc(tc.In)
		t.Must.Equal(tc.Expected, got)
	})
}

Output:
Example (ClassicStructured) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	myFunc := func(in int) string {
		if in == 42 {
			return "The Answer"
		}
		return "Not the answer"
	}
	type Case struct {
		Input    int
		Expected string
	}
	arrangements := map[string]Case{
		"when the input is correct": {
			Input:    42,
			Expected: "The Answer",
		},
		"when something else 1": {
			Input:    24,
			Expected: "Not the answer",
		},
		"when someting else 2": {
			Input:    128,
			Expected: "Not the answer",
		},
	}
	act := func(t *testcase.T, tc Case) {
		got := myFunc(tc.Input)
		t.Must.Equal(tc.Expected, got)
	}
	testcase.TableTest(t, arrangements, act)
}

Output:
Example (WithSpecBlock) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)

	var (
		in = testcase.Let[int](s, nil)
	)
	act := func(t *testcase.T) {
		// my act that use in
		_ = in.Get(t)
	}

	testcase.TableTest(s, map[string]func(s *testcase.Spec){
		"when 42": func(s *testcase.Spec) {
			in.LetValue(s, 42)
		},
		"whe 24": func(s *testcase.Spec) {
			in.LetValue(s, 42)
		},
	}, act)
}

Output:
Example (WithTestBlock) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)

	var (
		in = testcase.Let[int](s, nil)
	)
	act := func(t *testcase.T) {
		// my act that use in
		_ = in.Get(t)
	}

	testcase.TableTest(s, map[string]func(t *testcase.T){
		"when 42": func(t *testcase.T) {
			in.Set(t, 42)
		},
		"whe 24": func(t *testcase.T) {
			in.Set(t, 24)
		},
	}, act)
}

Output:

func UnsetEnv added in v0.28.0 

func UnsetEnv(tb testing.TB, key string)

UnsetEnv will unset the os environment variable value for the current program, and prepares a cleanup function to restore the original state of the environment variable.

Spec using this helper should be flagged with Spec.HasSideEffect or Spec.Sequential.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	testcase.UnsetEnv(tb, `MY_KEY`)
	// env will be restored after the test
}

Output:

Types

type Eventually added in v0.75.0 

type Eventually = assert.Eventually

Eventually

DEPRECATED: use assert.Eventually instead

type OpenSuite added in v0.79.0 

type OpenSuite interface {
	// Test is the function that assert expected behavioral requirements from a supplier implementation.
	// These behavioral assumptions made by the Consumer in order to simplify and stabilise its own code complexity.
	// Every time a Consumer makes an assumption about the behavior of the role interface supplier,
	// it should be clearly defined it with tests under this functionality.
	Test(*testing.T)
	// Benchmark will help with what to measure.
	// When you define a role interface contract, you should clearly know what performance aspects important for your Consumer.
	// Those aspects should be expressed in a form of Benchmark,
	// so different supplier implementations can be easily A/B tested from this aspect as well.
	Benchmark(*testing.B)
}

OpenSuite is a testcase independent testing suite interface standard.

type OpenSuiteAdapter added in v0.79.0 

type OpenSuiteAdapter struct{ OpenSuite }

func (OpenSuiteAdapter) Spec added in v0.79.0 

func (c OpenSuiteAdapter) Spec(s *Spec)

type RetryStrategy added in v0.25.0 

type RetryStrategy = assert.RetryStrategy

RetryStrategy

DEPRECATED: use assert.RetryStrategy instead

type RetryStrategyFunc added in v0.26.0 

type RetryStrategyFunc = assert.RetryStrategyFunc

RetryStrategyFunc

DEPRECATED: use assert.RetryStrategyFunc instead

type Spec 

type Spec struct {
	// contains filtered or unexported fields
}

Spec provides you a struct that makes building nested test spec easy with the core T#Context function.

spec structure is a simple wrapping around the testing.T#Context. It doesn't use any global singleton cache object or anything like that. It doesn't force you to use global vars.

It uses the same idiom as the core go testing pkg also provide you. You can use the same way as the core testing pkg 

go run ./... -v -run "the/name/of/the/test/it/print/orderingOutput/in/case/of/failure"

It allows you to do spec preparation for each test in a way, that it will be safe for use with testing.T#Parallel.

Example 
package main

import (
	"fmt"
	"strings"
	"testing"

	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/internal/example/mydomain"
	"github.com/adamluzsi/testcase/random"
)

func main() {
	var tb testing.TB

	// spec do not use any global magic
	// it is just a simple abstraction around testing.T#Context
	// Basically you can easily can run it as you would any other go testCase
	//   -> `go run ./... -v -run "my/edge/case/nested/block/I/want/to/run/only"`
	//
	spec := testcase.NewSpec(tb)

	// when you have no side effects in your testing suite,
	// you can enable parallel execution.
	// You can play parallel even from nested specs to apply parallel testing for that spec and below.
	spec.Parallel()
	// or
	spec.NoSideEffect()

	// testcase.variables are thread safe way of setting up complex contexts
	// where some variable need to have different values for edge cases.
	// and I usually work with in-memory implementation for certain shared specs,
	// to make my testCase coverage run fast and still close to somewhat reality in terms of integration.
	// and to me, it is a necessary thing to have "T#parallel" SpecOption safely available
	var myType = func(t *testcase.T) *mydomain.MyUseCase {
		return &mydomain.MyUseCase{}
	}

	// Each describe has a testing subject as an "act" function
	spec.Describe(`IsLower`, func(s *testcase.Spec) {
		var ( // inputs for the Act
			input = testcase.Var[string]{ID: `input`}
		)
		act := func(t *testcase.T) bool {
			return myType(t).IsLower(input.Get(t))
		}

		s.When(`input string has lower case characters`, func(s *testcase.Spec) {
			input.Let(s, func(t *testcase.T) string {
				return t.Random.StringNWithCharset(t.Random.Int(), strings.ToLower(random.CharsetAlpha()))
			})

			s.And(`the first character is capitalized`, func(s *testcase.Spec) {
				// you can add more nesting for more concrete specifications,
				// in each nested block, you work on a separate variable stack,
				// so even if you overwrite something here,
				// that has no effect outside of this scope
				s.Before(func(t *testcase.T) {
					upperCaseLetter := t.Random.StringNC(1, strings.ToUpper(random.CharsetAlpha()))
					input.Set(t, upperCaseLetter+input.Get(t))
				})

				s.Then(`it will report false`, func(t *testcase.T) {
					t.Must.True(act(t),
						fmt.Sprintf(`it was expected that %q will be reported to be not lowercase`, input.Get(t)))
				})

			})

			s.Then(`it will return true`, func(t *testcase.T) {
				t.Must.True(act(t),
					fmt.Sprintf(`it was expected that the %q will re reported to be lowercase`, input.Get(t)))
			})
		})

		s.When(`input string has upcase case characters`, func(s *testcase.Spec) {
			input.Let(s, func(t *testcase.T) string {
				return t.Random.StringNWithCharset(t.Random.Int(), strings.ToUpper(random.CharsetAlpha()))
			})

			s.Then(`it will return false`, func(t *testcase.T) {
				t.Must.False(act(t))
			})
		})
	})
}

Output:
Example (WhenProjectUseSharedSpecificationHelpers) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/internal/example/mydomain"
	"github.com/adamluzsi/testcase/internal/example/spechelper"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	myType := func() *mydomain.MyUseCase { return &mydomain.MyUseCase{} }

	s.Describe(`#MyFunc`, func(s *testcase.Spec) {
		var (
			something = spechelper.GivenWeHaveSomething(s)
			// .. other givens
		)
		act := func(t *testcase.T) {
			myType().MyFuncThatNeedsSomething(something.Get(t))
		}

		s.Then(`test case described here`, func(t *testcase.T) {
			act(t)
		})
	})
}

Output:
Example (WithBenchmark) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/internal/example/mydomain"
)

func main() {
	var b *testing.B
	s := testcase.NewSpec(b)

	myType := func(t *testcase.T) *mydomain.MyUseCase {
		return &mydomain.MyUseCase{}
	}

	s.When(`something`, func(s *testcase.Spec) {
		s.Before(func(t *testcase.T) {
			t.Log(`setup`)
		})

		s.Then(`this benchmark block will be executed by *testing.B.N times`, func(t *testcase.T) {
			myType(t).IsLower(`Hello, World!`)
		})
	})
}

Output:

func NewSpec 

func NewSpec(tb testing.TB, opts ...SpecOption) *Spec

NewSpec create new Spec struct that is ready for usage.

func ToSpec added in v0.109.0 

func ToSpec[TBS anyTBOrSpec](tbs TBS) *Spec

func (*Spec) After 

func (spec *Spec) After(afterBlock tBlock)

After give you the ability to run a block after each test case. This is ideal for running cleanups. The received *testing.T object is the same as the Then block *testing.T object This hook applied to this scope and anything that is nested from here. All setup block is stackable.

DEPRECATED: use Spec.Before with T.Cleanup or Spec.Before with T.Defer instead

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	s.After(func(t *testcase.T) {
		// this will run after the test cases.
		// this hook applied to this scope and anything that is nested from here.
		// hooks can be stacked with each call.
	})
}

Output:

func (*Spec) AfterAll added in v0.52.0 

func (spec *Spec) AfterAll(blk func(tb testing.TB))

AfterAll give you the ability to create a hook that runs only once after all the test cases already ran.

DEPRECATED: use Spec.BeforeAll with testing.TB#Cleanup

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	s.AfterAll(func(tb testing.TB) {
		// this will run once all the test case already ran.
	})
}

Output:

func (*Spec) And 

func (spec *Spec) And(desc string, testContextBlock sBlock, opts ...SpecOption)

And is an alias for testcase#Spec.Context And is used to represent additional requirement for reaching a certain testing runtime contexts.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	s.When(`some spec`, func(s *testcase.Spec) {
		// fulfil the spec

		s.And(`additional spec`, func(s *testcase.Spec) {

			s.Then(`assert`, func(t *testcase.T) {

			})
		})

		s.And(`additional spec opposite`, func(s *testcase.Spec) {

			s.Then(`assert`, func(t *testcase.T) {

			})
		})
	})
}

Output:

func (*Spec) Around 

func (spec *Spec) Around(block hookBlock)

Around give you the ability to create "Before" setup for each test case, with the additional ability that the returned function will be deferred to run after the Then block is done. This is ideal for setting up mocks, and then return the assertion request calls in the return func. This hook applied to this scope and anything that is nested from here. All setup block is stackable.

DEPRECATED: use Spec.Before with T.Cleanup or Spec.Before with T.Defer instead

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	s.Around(func(t *testcase.T) func() {
		// this will run before the test cases

		// this hook applied to this scope and anything that is nested from here.
		// hooks can be stacked with each call
		return func() {
			// The content of the returned func will be deferred to run after the test cases.
		}
	})
}

Output:

func (*Spec) AroundAll added in v0.52.0 

func (spec *Spec) AroundAll(blk func(tb testing.TB) func())

AroundAll give you the ability to create a hook that first run before all test, then the returned lambda will run after the test cases.

DEPRECATED: use Spec.BeforeAll with testing.TB#Cleanup

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	s.AroundAll(func(tb testing.TB) func() {
		// this will run once before all the test case.
		return func() {
			// this will run once after all the test case already ran.
		}
	})
}

Output:

func (*Spec) Before 

func (spec *Spec) Before(beforeBlock tBlock)

Before give you the ability to run a block before each test case. This is ideal for doing clean ahead before each test case. The received *testing.T object is the same as the Test block *testing.T object This hook applied to this scope and anything that is nested from here. All setup block is stackable.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	s.Before(func(t *testcase.T) {
		// this will run before the test cases.
	})
}

Output:

func (*Spec) BeforeAll added in v0.52.0 

func (spec *Spec) BeforeAll(blk func(tb testing.TB))

BeforeAll give you the ability to create a hook that runs only once before the test cases.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	s.BeforeAll(func(tb testing.TB) {
		// this will run once before every test cases.
	})
}

Output:

func (*Spec) Context 

func (spec *Spec) Context(desc string, testContextBlock sBlock, opts ...SpecOption)

Context allow you to create a sub specification for a given spec. In the sub-specification it is expected to add more contextual information to the test in a form of hook of variable setting. With Context you can set your custom test description, without any forced prefix like describe/when/and.

It is basically piggybacking the testing#T.Context and create new subspec in that nested testing#T.Context scope. It is used to add more description spec for the given subject. It is highly advised to always use When + Before/Around together, in which you should setup exactly what you wrote in the When description input. You can Context as many When/And within each other, as you want to achieve the most concrete edge case you want to test.

To verify easily your state-machine, you can count the `if`s in your implementation, and check that each `if` has 2 `When` block to represent the two possible path.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	s.Context(`description of the testing spec`, func(s *testcase.Spec) {
		s.Before(func(t *testcase.T) {
			// prepare for the testing spec
		})

		s.Then(`assert expected outcome`, func(t *testcase.T) {

		})
	})
}

Output:

func (*Spec) Describe 

func (spec *Spec) Describe(subjectTopic string, specification sBlock, opts ...SpecOption)

Describe creates a new spec scope, where you usually describe a subject.

By convention it is highly advised to create a variable `subject` with function that share the return signature of the method you test on a structure, and take *testcase.variables as the only input value. If your method require input values, you should strictly set those values within a `When`/`And` scope. This ensures you have to think trough the possible state-machines paths that are based on the input values.

For functions where 2 value is returned, and the second one is an error, in order to avoid repetitive test cases in the `Then` I often define a `onSuccess` variable, with a function that takes `testcase#variables` as well and test error return value there with `testcase#variables.T()`.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/internal/example/mydomain"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	myType := testcase.Let(s, func(t *testcase.T) *mydomain.MyUseCase {
		return &mydomain.MyUseCase{}
	})

	// Describe description points orderingOutput the subject of the tests
	s.Describe(`#IsLower`, func(s *testcase.Spec) {
		var (
			input   = testcase.Var[string]{ID: `input`}
			subject = func(t *testcase.T) bool {
				// subject should represent what will be tested in the describe block
				return myType.Get(t).IsLower(input.Get(t))
			}
		)

		s.Test(``, func(t *testcase.T) { subject(t) })
	})
}

Output:

func (*Spec) Finish added in v0.29.0 

func (spec *Spec) Finish()

Finish executes all unfinished test and mark them finished. Finish can be used when it is important to run the test before the Spec's testing#TB.Cleanup would execute.

Such case can be when a resource leaked inside a testing scope and resource closed with a deferred function, but the spec is still not ran.

func (*Spec) HasSideEffect added in v0.9.0 

func (spec *Spec) HasSideEffect()

HasSideEffect means that after this call things defined that has software side effect during runtime. This suggest on its own that execution should be sequential in order to avoid retry tests.

HasSideEffect and NoSideEffect can be used together to describe a given piece of specification properties. Using them at the same location makes little sense, it was intended to be used in spec helper package where setup function handles what resource should be used in the spec variables. This allows flexibility for the developers to use side effect free variant for local development that has quick feedback loop, and replace them with the production implementation during CI/CD pipeline which less time critical.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)
	// this mark the testCase to contain side effects.
	// this forbids any parallel testCase execution to avoid retry tests.
	//
	// Under the hood this is a syntax sugar for Sequential
	s.HasSideEffect()

	s.Test(`this will run in sequence`, func(t *testcase.T) {})

	s.Context(`some spec`, func(s *testcase.Spec) {
		s.Test(`this run in sequence`, func(t *testcase.T) {})

		s.Test(`this run in sequence`, func(t *testcase.T) {})
	})
}

Output:

func (*Spec) Let 

func (spec *Spec) Let(varName string, blk VarInit[any]) Var[any]

Let is a method to provide backward compatibility with the existing testing suite. Due to how Go type parameters work, methods are not allowed to have type parameters, thus Let has moved to be a pkg-level function in the package.

DEPRECATED: use testcase.Let instead testcase#Spec.Let.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	myTestVar := testcase.Let(s, func(t *testcase.T) interface{} {
		return "value that needs complex construction or can be mutated"
	})

	s.Then(`test case`, func(t *testcase.T) {
		t.Log(myTestVar.Get(t)) // -> returns the value set in the current spec spec for MyTestVar
	})
}

Output:
Example (EagerLoading) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	myTestVar := testcase.Let(s, func(t *testcase.T) interface{} {
		return "value that will be eager loaded before the testCase/then block reached"
	}).EagerLoading(s)
	// EagerLoading will ensure that the value of this Spec Var will be evaluated during the preparation of the testCase.

	s.Then(`test case`, func(t *testcase.T) {
		t.Log(myTestVar.Get(t))
	})
}

Output:
Example (SqlDB) 
package main

import (
	"context"
	"database/sql"
	"testing"

	"github.com/adamluzsi/testcase"
)

type SupplierWithDBDependency struct {
	DB interface {
		QueryContext(ctx context.Context, query string, args ...interface{}) (*sql.Rows, error)
	}
}

func (s SupplierWithDBDependency) DoSomething(ctx context.Context) error {
	rows, err := s.DB.QueryContext(ctx, `SELECT 1 = 1`)
	if err != nil {
		return err
	}
	return rows.Close()
}

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	var (
		tx = testcase.Let(s, func(t *testcase.T) *sql.Tx {
			// it is advised to use a persistent db connection between multiple specification runs,
			// because otherwise `go testCase -count $times` can receive random connection failures.
			tx, err := getDBConnection(t).Begin()
			if err != nil {
				t.Fatal(err.Error())
			}
			// testcase.T#Defer will execute the received function after the current testCase edge case
			// where the `tx` testCase variable were accessed.
			t.Defer(tx.Rollback)
			return tx
		})
		supplier = testcase.Let(s, func(t *testcase.T) SupplierWithDBDependency {
			return SupplierWithDBDependency{DB: tx.Get(t)}
		})
	)

	s.Describe(`#DoSomething`, func(s *testcase.Spec) {
		var (
			ctx = testcase.Let(s, func(t *testcase.T) context.Context {
				return context.Background()
			})
			subject = func(t *testcase.T) error {
				return supplier.Get(t).DoSomething(ctx.Get(t))
			}
		)

		s.When(`...`, func(s *testcase.Spec) {
			s.Before(func(t *testcase.T) {
				//...
			})

			s.Then(`...`, func(t *testcase.T) {
				t.Must.Nil(subject(t))
			})
		})
	})
}

func getDBConnection(_ testing.TB) *sql.DB {

	return nil
}

Output:
Example (TestingDouble) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/internal/doubles"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	stubTB := testcase.Let(s, func(t *testcase.T) *doubles.TB {
		stub := &doubles.TB{}
		t.Defer(stub.Finish)
		return stub
	})

	s.When(`some scope where double should behave in a certain way`, func(s *testcase.Spec) {
		s.Before(func(t *testcase.T) {
			stubTB.Get(t).StubName = "my stubbed name"
		})

		s.Then(`double will be available in every test case and finishNow called afterwards`, func(t *testcase.T) {
			// ...
		})
	})
}

Output:
Example (UsageWithinNestedScope) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/internal/example/mydomain"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	var myType = func(t *testcase.T) *mydomain.MyUseCase { return &mydomain.MyUseCase{} }

	s.Describe(`#IsLower`, func(s *testcase.Spec) {
		var (
			input   = testcase.Var[string]{ID: `input`}
			subject = func(t *testcase.T) bool {
				return myType(t).IsLower(input.Get(t))
			}
		)

		s.When(`input characters are list lowercase`, func(s *testcase.Spec) {
			testcase.Let(s, func(t *testcase.T) interface{} {
				return "list lowercase"
			})
			// or
			input.Let(s, func(t *testcase.T) string {
				return "list lowercase"
			})

			s.Then(`it will report true`, func(t *testcase.T) {
				t.Must.True(subject(t))
			})
		})

		s.When(`input is a capitalized`, func(s *testcase.Spec) {
			testcase.Let(s, func(t *testcase.T) interface{} {
				return "Capitalized"
			})
			// or
			input.Let(s, func(t *testcase.T) string {
				return "Capitalized"
			})

			s.Then(`it will report false`, func(t *testcase.T) {
				t.Must.True(!subject(t))
			})
		})
	})
}

Output:

func (*Spec) LetValue added in v0.2.1 

func (spec *Spec) LetValue(varName string, value any) Var[any]

LetValue is a method to provide backward compatibility with the existing testing suite. Due to how Go type parameters work, methods are not allowed to have type parameters, thus LetValue has moved to be a pkg-level function in the package.

DEPRECATED: use testcase.LetValue instead testcase#Spec.LetValue.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	variable := testcase.LetValue(s, "value")

	s.Then(`test case`, func(t *testcase.T) {
		t.Log(variable.Get(t)) // -> "value"
	})
}

Output:
Example (UsageWithinNestedScope) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/internal/example/mydomain"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	var myType = func(t *testcase.T) *mydomain.MyUseCase { return &mydomain.MyUseCase{} }

	s.Describe(`#IsLower`, func(s *testcase.Spec) {
		var (
			input   = testcase.Var[string]{ID: `input`}
			subject = func(t *testcase.T) bool {
				return myType(t).IsLower(input.Get(t))
			}
		)

		s.When(`input characters are list lowercase`, func(s *testcase.Spec) {
			testcase.LetValue(s, "list lowercase")
			// or
			input.LetValue(s, "list lowercase")

			s.Then(`it will report true`, func(t *testcase.T) {
				t.Must.True(subject(t))
			})
		})

		s.When(`input is a capitalized`, func(s *testcase.Spec) {
			testcase.LetValue(s, "Capitalized")
			// or
			input.LetValue(s, "Capitalized")

			s.Then(`it will report false`, func(t *testcase.T) {
				t.Must.True(!subject(t))
			})
		})
	})
}

Output:

func (*Spec) NoSideEffect added in v0.2.1 

func (spec *Spec) NoSideEffect()

NoSideEffect gives a hint to the reader of the current test that during the test execution, no side effect outside from the test specification scope is expected to be observable. It is important to note that this flag primary meant to represent the side effect possibility to the outside of the current testing specification, and not about the test specification's subject.

It is safe to state that if the subject of the test specification has no side effect, then the test specification must have no side effect as well.

If the subject of the test specification do side effect on an input value, then the test specification must have no side effect, as long Let memorization is used.

If the subject of the test specification does mutation on global variables such as OS Variable states for the current process, then it is likely, that even if the changes by the mutation is restored as part of the test specification, the test specification has side effects that would affect other test specification results, and, as such, must be executed sequentially.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)
	// this is an idiom to express that the subject in the tests here are not expected to have any side-effect.
	// this means they are safe to be executed in parallel.
	s.NoSideEffect()

	s.Test(`this will run in parallel`, func(t *testcase.T) {})

	s.Context(`some spec`, func(s *testcase.Spec) {
		s.Test(`this run in parallel`, func(t *testcase.T) {})

		s.Test(`this run in parallel`, func(t *testcase.T) {})
	})
}

Output:

func (*Spec) Parallel 

func (spec *Spec) Parallel()

Parallel allows you to set list test case for the spec where this is being called, and below to nested contexts, to be executed in parallel (concurrently). Keep in mind that you can call Parallel even from nested specs to apply Parallel testing for that spec and below. This is useful when your test suite has no side effects at list. Using values from *vars when Parallel is safe. It is a shortcut for executing *testing.T#Parallel() for each test

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)
	s.Parallel() // tells the specs to run list test case in parallel

	s.Test(`this will run in parallel`, func(t *testcase.T) {})

	s.Context(`some spec`, func(s *testcase.Spec) {
		s.Test(`this run in parallel`, func(t *testcase.T) {})

		s.Test(`this run in parallel`, func(t *testcase.T) {})
	})
}

Output:
Example (ScopedWithContext) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	s.Context(`spec marked parallel`, func(s *testcase.Spec) {
		s.Parallel()

		s.Test(`this run in parallel`, func(t *testcase.T) {})
	})

	s.Context(`spec without parallel`, func(s *testcase.Spec) {

		s.Test(`this will run in sequence`, func(t *testcase.T) {})
	})
}

Output:

func (*Spec) Sequential added in v0.9.0 

func (spec *Spec) Sequential()

Sequential allows you to set list test case for the spec where this is being called, and below to nested contexts, to be executed sequentially. It will negate any testcase.Spec#Parallel call effect. This is useful when you want to create a spec helper package and there you want to manage if you want to use components side effects or not.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)
	s.Sequential() // tells the specs to run list test case in sequence

	s.Test(`this will run in sequence`, func(t *testcase.T) {})

	s.Context(`some spec`, func(s *testcase.Spec) {
		s.Test(`this run in sequence`, func(t *testcase.T) {})

		s.Test(`this run in sequence`, func(t *testcase.T) {})
	})
}

Output:
Example (GlobalVar) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/internal/example/spechelper"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	// might or might not allow parallel execution
	// It depends on the
	storage := spechelper.Storage.Bind(s)

	// Tells that the subject of this specification should be software side effect free on its own.
	s.NoSideEffect()

	s.Test("will only run parallel if no dependency has side effect", func(t *testcase.T) {
		t.Logf("%#v", storage.Get(t))
	})
}

Output:
Example (ScopedWithContext) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	s.Parallel() // on top level, spec marked as parallel

	s.Context(`spec marked sequential`, func(s *testcase.Spec) {
		s.Sequential() // but in subcontext the testCase marked as sequential

		s.Test(`this run in sequence`, func(t *testcase.T) {})
	})

	s.Context(`spec that inherit parallel flag`, func(s *testcase.Spec) {

		s.Test(`this will run in parallel`, func(t *testcase.T) {})
	})
}

Output:

func (*Spec) SkipBenchmark added in v0.23.0 

func (spec *Spec) SkipBenchmark()

SkipBenchmark will flag the current Spec / Context to be skipped during Benchmark mode execution. If you wish to skip only a certain test, not the whole Spec / Context, use the SkipBenchmark SpecOption instead.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var b *testing.B
	s := testcase.NewSpec(b)
	s.SkipBenchmark()

	s.Test(`this will be skipped during benchmark`, func(t *testcase.T) {})

	s.Context(`some spec`, func(s *testcase.Spec) {
		s.Test(`this as well`, func(t *testcase.T) {})
	})
}

Output:
Example (ScopedWithContext) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var b *testing.B
	s := testcase.NewSpec(b)

	s.When(`rainy path`, func(s *testcase.Spec) {
		s.SkipBenchmark()

		s.Test(`will be skipped during benchmark`, func(t *testcase.T) {})
	})

	s.Context(`happy path`, func(s *testcase.Spec) {
		s.Test(`this will run as benchmark`, func(t *testcase.T) {})
	})
}

Output:

func (*Spec) Tag added in v0.10.0 

func (spec *Spec) Tag(tags ...string)

Tag allow you to mark tests in the current and below specification scope with tags. This can be used to provide additional documentation about the nature of the testing scope. This later might be used as well to filter your test in your CI/CD pipeline to build separate testing stages like integration, e2e and so on.

To select or exclude tests with certain tags, you can provide a comma separated list to the following environment variables:

  • TESTCASE_TAG_INCLUDE to filter down to test with a certain tag
  • TESTCASE_TAG_EXCLUDE to exclude certain test from the overall testing scope.

They can be combined as well.

example usage: 

TESTCASE_TAG_INCLUDE='E2E' go test ./...
TESTCASE_TAG_EXCLUDE='E2E' go test ./...
TESTCASE_TAG_INCLUDE='E2E' TESTCASE_TAG_EXCLUDE='list,of,excluded,tags' go test ./...
Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	// example usage:
	// 	TESTCASE_TAG_INCLUDE='E2E' go testCase ./...
	// 	TESTCASE_TAG_EXCLUDE='E2E' go testCase ./...
	// 	TESTCASE_TAG_INCLUDE='E2E' TESTCASE_TAG_EXCLUDE='list,of,excluded,tags' go testCase ./...
	//
	var t *testing.T
	s := testcase.NewSpec(t)

	s.Context(`E2E`, func(s *testcase.Spec) {
		// by tagging the spec spec, we can filter tests orderingOutput later in our CI/CD pipeline.
		// A comma separated list can be set with TESTCASE_TAG_INCLUDE env variable to filter down to tests with certain tags.
		// And/Or a comma separated list can be provided with TESTCASE_TAG_EXCLUDE to exclude tests tagged with certain tags.
		s.Tag(`E2E`)

		s.Test(`some E2E testCase`, func(t *testcase.T) {
			// ...
		})
	})
}

Output:

func (*Spec) Test 

func (spec *Spec) Test(desc string, test tBlock, opts ...SpecOption)

Test creates a test case block where you receive the fully configured `testcase#T` object. Hook contents that meant to run before the test edge cases will run before the function the Test receives, and hook contents that meant to run after the test edge cases will run after the function is done. After hooks are deferred after the received function block, so even in case of panic, it will still be executed.

It should not contain anything that modify the test subject input. It should focuses only on asserting the result of the subject.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	s.Test(`my testCase description`, func(t *testcase.T) {
		// ...
	})
}

Output:

func (*Spec) Then 

func (spec *Spec) Then(desc string, test tBlock, opts ...SpecOption)

Then is an alias for Test

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	s.Then(`it is expected.... so this is the testCase description here`, func(t *testcase.T) {
		// ...
	})
}

Output:

func (*Spec) When 

func (spec *Spec) When(desc string, testContextBlock sBlock, opts ...SpecOption)

When is an alias for testcase#Spec.Context When is used usually to represent `if` based decision reasons about your testing subject.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/internal/example/mydomain"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	var (
		myType  = func(t *testcase.T) *mydomain.MyUseCase { return &mydomain.MyUseCase{} }
		input   = testcase.Var[string]{ID: `input`}
		subject = func(t *testcase.T) bool { return myType(t).IsLower(input.Get(t)) }
	)

	s.When(`input has only upcase letter`, func(s *testcase.Spec) {
		input.LetValue(s, "UPPER")

		s.Then(`it will be false`, func(t *testcase.T) {
			t.Must.True(!subject(t))
		})
	})

	s.When(`input has only lowercase letter`, func(s *testcase.Spec) {
		input.LetValue(s, "lower")

		s.Then(`it will be true`, func(t *testcase.T) {
			t.Must.True(subject(t))
		})
	})
}

Output:

type SpecOption added in v0.28.0 

type SpecOption interface {
	// contains filtered or unexported methods
}

func Flaky added in v0.23.0 

func Flaky(CountOrTimeout interface{}) SpecOption

Flaky will mark the spec/testCase as unstable. Flaky testCase execution is tolerant towards failing assertion and these tests will be rerun in case of a failure. A Wait Timeout for a successful flaky testCase must be provided.

The primary use-case is that when a team focus on shipping orderingOutput the value, and time is short till deadlines. These flaky tests prevent CI/CD pipelines often turned off in the heat of the moment to let pass the latest changes. The motivation behind is to gain time for the team to revisit these tests after the release and then learn from it. At the same time, they intend to fix it as well. These tests, however often forgotten, and while they are not the greatest assets of the CI pipeline, they often still serve essential value.

As a Least wrong solution, instead of skipping these tests, you can mark them as flaky, so in a later time, finding these flaky tests in the project should be easy. When you flag a testCase as flaky, you must provide a timeout value that will define a testing time window where the testCase can be rerun multiple times by the framework. If the testCase can't run successfully within this time-window, the testCase will fail. This failure potentially means that the underlying functionality is broken, and the committer should reevaluate the changes in the last commit.

While this functionality might help in tough times, it is advised to pair the usage with a scheduled monthly CI pipeline job. The Job should check the testing code base for the flaky flag.

Example (RetryNTimes) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)

	s.Test(`testCase with "random" fails`, func(t *testcase.T) {
		// This testCase might fail "randomly" but the retry flag will allow some tolerance
		// This should be used to find time in team's calendar
		// and then allocate time outside of death-march times to learn to avoid retry tests in the future.
	}, testcase.Flaky(42))
}

Output:
Example (RetryUntilTimeout) 
package main

import (
	"testing"
	"time"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)

	s.Test(`testCase with "random" fails`, func(t *testcase.T) {
		// This testCase might fail "randomly" but the retry flag will allow some tolerance
		// This should be used to find time in team's calendar
		// and then allocate time outside of death-march times to learn to avoid retry tests in the future.
	}, testcase.Flaky(time.Minute))
}

Output:

func Group added in v0.23.5 

func Group(name string) SpecOption

Group creates a testing group in the specification. During testCase execution, a group will be bundled together, and parallel tests will run concurrently within the the testing group.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)

	s.Context(`description`, func(s *testcase.Spec) {

		s.Test(``, func(t *testcase.T) {})

	}, testcase.Group(`testing-group-group-that-can-be-even-targeted-with-testCase-run-cli-option`))
}

Output:

func RetryStrategyForEventually added in v0.59.0 

func RetryStrategyForEventually(strategy assert.RetryStrategy) SpecOption

func SkipBenchmark added in v0.20.0 

func SkipBenchmark() SpecOption
Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)

	s.Test(`will run`, func(t *testcase.T) {
		// this will run during benchmark execution
	})

	s.Test(`will skip`, func(t *testcase.T) {
		// this will skip the benchmark execution
	}, testcase.SkipBenchmark())
}

Output:

type StubTB added in v0.74.0 

type StubTB = doubles.TB

StubTB is a stub that implements testing.TB

Example (TestingATestHelper) 
package main

import (
	"fmt"
	"testing"

	"github.com/adamluzsi/testcase/assert"
	"github.com/adamluzsi/testcase/internal/doubles"
)

func main() {
	stub := &doubles.TB{}
	stub.Log("hello", "world")
	fmt.Println(stub.Logs.String())

	myTestHelper := func(tb testing.TB) {
		tb.FailNow()
	}

	var tb testing.TB
	assert.Must(tb).Panic(func() {
		myTestHelper(stub)
	})
	assert.Must(tb).True(stub.IsFailed)
}

Output:

type Suite added in v0.79.0 

type Suite interface {
	// Spec defines the tests on the received *Spec object.
	Spec(s *Spec)
}

Suite meant to represent a testing suite. A test Suite is a collection of test cases. In a test suite, the test cases are organized in a logical order. A Suite is a great tool to define interface testing suites (contracts).

type T 

type T struct {
	// TB is the interface common to T and B.
	testing.TB
	// Random is a random generator that uses the Spec seed.
	//
	// When a test fails with random input from Random generator,
	// the failed test scenario can be recreated simply by providing the same TESTCASE_SEED
	// as you can read from the console output of the failed test.
	Random *random.Random
	// It provides asserters to make assertion easier.
	// Must Interface will use FailNow on a failed assertion.
	// This will make test exit early on.
	// Should Interface's will allow to continue the test scenario,
	// but mark test failed on a failed assertion.
	assert.It
	// contains filtered or unexported fields
}

T embeds both testcase vars, and testing#T functionality. This leave place open for extension and but define a stable foundation for the hooks and testCase edge case function signatures

Works as a drop in replacement for packages where they depend on one of the function of testing#T

Example (Must) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)
	s.Test(``, func(t *testcase.T) {
		// failed test will stop with FailNow
		t.Must.Equal(1, 1, "must be equal")
	})
}

Output:
Example (Random) 
package main

import (
	"testing"
	"time"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)
	s.Test(``, func(t *testcase.T) {
		_ = t.Random.Int()
		_ = t.Random.IntBetween(0, 42)
		_ = t.Random.IntN(42)
		_ = t.Random.Float32()
		_ = t.Random.Float64()
		_ = t.Random.String()
		_ = t.Random.StringN(42)
		_ = t.Random.StringNWithCharset(42, "abc")
		_ = t.Random.Bool()
		_ = t.Random.Time()
		_ = t.Random.TimeN(time.Now(), 0, 4, 2)
		_ = t.Random.TimeBetween(time.Now().Add(-1*time.Hour), time.Now().Add(time.Hour))
		_ = t.Random.ElementFromSlice([]int{1, 2, 3}).(int)
		_ = t.Random.KeyFromMap(map[string]struct{}{`foo`: {}, `bar`: {}, `baz`: {}}).(string)
	})
}

Output:
Example (Should) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)
	s.Test(``, func(t *testcase.T) {
		// failed test will proceed, but mart the test failed
		t.Should.Equal(1, 1, "should be equal")
	})
}

Output:

func NewT added in v0.47.0 

func NewT(tb testing.TB, spec *Spec) *T

NewT returns a *testcase.T prepared for the given testing.TB

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	variable := testcase.Var[int]{ID: "variable", Init: func(t *testcase.T) int {
		return t.Random.Int()
	}}

	// flat test case with test runtime variable caching
	var tb testing.TB
	t := testcase.NewT(tb, testcase.NewSpec(tb))
	value1 := variable.Get(t)
	value2 := variable.Get(t)
	t.Logf(`test case variable caching works even in flattened tests: v1 == v2 -> %v`, value1 == value2)
}

Output:

func ToT added in v0.109.0 

func ToT[TBs anyTB](tb TBs) *T

func (*T) Cleanup added in v0.19.0 

func (t *T) Cleanup(fn func())

func (*T) Defer added in v0.2.1 

func (t *T) Defer(fn interface{}, args ...interface{})

Defer function defers the execution of a function until the current test case returns. Deferred functions are guaranteed to run, regardless of panics during the test case execution. Deferred function calls are pushed onto a testcase runtime stack. When an function passed to the Defer function, it will be executed as a deferred call in last-in-first-orderingOutput order.

It is advised to use this inside a testcase.Spec#Let memorization function when spec variable defined that has finalizer requirements. This allow the specification to ensure the object finalizer requirements to be met, without using an testcase.Spec#After where the memorized function would be executed always, regardless of its actual need.

In a practical example, this means that if you have common vars defined with testcase.Spec#Let memorization, which needs to be Closed for example, after the test case already run. Ensuring such objects Close call in an after block would cause an initialization of the memorized object list the time, even in tests where this is not needed.

e.g.:

  • mock initialization with mock controller, where the mock controller #Finish function must be executed after each testCase suite.
  • sql.DB / sql.Tx
  • basically anything that has the io.Closer interface
Example 
package main

import (
	"database/sql"
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	// db for example is something that needs to defer an action after the testCase run
	db := testcase.Let(s, func(t *testcase.T) *sql.DB {
		db, err := sql.Open(`driverName`, `dataSourceName`)

		// asserting error here with the *testcase.T ensure that the testCase will don't have some spooky failure.
		t.Must.Nil(err)

		// db.Close() will be called after the current test case reach the teardown hooks
		t.Defer(db.Close)

		// check if connection is OK
		t.Must.Nil(db.Ping())

		// return the verified db instance for the caller
		// this db instance will be memorized during the runtime of the test case
		return db
	})

	s.Test(`a simple test case`, func(t *testcase.T) {
		db := db.Get(t)
		t.Must.Nil(db.Ping()) // just to do something with it.
	})
}

Output:
Example (WithArgs) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	something := testcase.Let(s, func(t *testcase.T) *ExampleDeferTeardownWithArgs {
		ptr := &ExampleDeferTeardownWithArgs{}
		// T#Defer arguments copied upon pass by value
		// and then passed to the function during the execution of the deferred function call.
		//
		// This is ideal for situations where you need to guarantee that a value cannot be muta
		t.Defer(ptr.SomeTeardownWithArg, `Hello, World!`)
		return ptr
	})

	s.Test(`a simple test case`, func(t *testcase.T) {
		entity := something.Get(t)

		entity.DoSomething()
	})
}

type ExampleDeferTeardownWithArgs struct{}

func (*ExampleDeferTeardownWithArgs) SomeTeardownWithArg(_ string) {}

func (*ExampleDeferTeardownWithArgs) DoSomething() {}

Output:

func (*T) Eventually added in v0.59.0 

func (t *T) Eventually(blk func(it assert.It), retryOpts ...interface{})

Eventually helper allows you to write expectations to results that will only be eventually true. A common scenario where using Eventually will benefit you is testing concurrent operations. Due to the nature of async operations, one might need to wait and observe the system with multiple tries before the outcome can be seen. Eventually will attempt to assert multiple times with the assertion function block, until the expectations in the function body yield no testing failure. Calling multiple times the assertion function block content should be a safe and repeatable operation. For more, read the documentation of Eventually and Eventually.Assert. In case Spec doesn't have a configuration for how to retry Eventually, the DefaultEventually will be used.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/assert"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)
	s.Test(``, func(t *testcase.T) {
		// Eventually this will pass eventually
		t.Eventually(func(it assert.It) {
			it.Must.True(t.Random.Bool())
		})
	})
}

Output:

func (*T) HasTag added in v0.10.2 

func (t *T) HasTag(tag string) bool
Example 
package main

import (
	"context"
	"database/sql"
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	var s = testcase.NewSpec(t)

	type DB interface { // header interface in supplier pkg
		QueryRowContext(ctx context.Context, query string, args ...interface{}) *sql.Row
	}
	testcase.Let(s, func(t *testcase.T) DB {
		db, err := sql.Open(`driverName`, `dataSourceName`)
		t.Must.Nil(err)

		if t.HasTag(`black box`) {
			// tests with black box  use http testCase server or similar things and high level tx management not maintainable.
			t.Defer(db.Close)
			return db
		}

		tx, err := db.BeginTx(context.Background(), nil)
		t.Must.Nil(err)
		t.Defer(tx.Rollback)
		return tx
	})
}

Output:

func (*T) LogPretty added in v0.115.0 

func (t *T) LogPretty(vs ...any)

LogPretty will Log out values in pretty print format (pp.Format).

Example 
package main

import (
	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testcase.T

	type X struct {
		Foo string
	}

	t.LogPretty(X{Foo: "hello"})
	// Logs:
	// 	testcase_test.X{
	// 		Foo: "hello",
	// 	}
}

Output:

func (*T) SetEnv added in v0.105.0 

func (t *T) SetEnv(key, value string)

SetEnv will set the os environment variable for the current program to a given value, and prepares a cleanup function to restore the original state of the environment variable.

This cannot be used in parallel tests.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)

	s.Test("", func(t *testcase.T) {
		t.SetEnv("key", "value")
	})
}

Output:

func (*T) Setenv added in v0.105.0 

func (t *T) Setenv(key, value string)

Setenv calls os.Setenv(key, value) and uses Cleanup to restore the environment variable to its original value after the test.

This cannot be used in parallel tests.

func (*T) SkipUntil added in v0.78.0 

func (t *T) SkipUntil(year int, month time.Month, day int)

SkipUntil is equivalent to Log followed by SkipNow if the test is executing prior to the given deadline time. SkipUntil is useful when you need to skip something temporarily, but you don't trust your memory enough to return to it on your own.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	s.Test(`will be skipped`, func(t *testcase.T) {
		// make tests skip until the given day is reached,
		// then make the tests fail.
		// This helps to commit code which still work in progress.
		t.SkipUntil(2020, 01, 01)
	})

	s.Test(`will not be skipped`, func(t *testcase.T) {})
}

Output:

func (*T) UnsetEnv added in v0.105.0 

func (t *T) UnsetEnv(key string)

UnsetEnv will unset the os environment variable value for the current program, and prepares a cleanup function to restore the original state of the environment variable.

This cannot be used in parallel tests.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)

	s.Test("", func(t *testcase.T) {
		t.UnsetEnv("key")
	})
}

Output:

type TBRunner added in v0.37.0 

type TBRunner interface {
	testing.TB
	// Run runs blk as a subtest of TBRunner called group. It runs blk in a separate goroutine
	// and blocks until blk returns or calls t.parallel to become a parallel testCase.
	// Run reports whether blk succeeded (or at least did not fail before calling t.parallel).
	//
	// Run may be called simultaneously from multiple goroutines, but list such calls
	// must return before the outer testCase function for t returns.
	Run(name string, blk func(tb testing.TB)) bool
}

TBRunner defines the interface you need to implement if you want to create a custom TB that is compatible with Spec. To implement TBRunner correctly please use contracts.TB 

import (
	"github.com/adamluzsi/testcase/contracts"
	"testing"
)

func TestMyTestRunner(t *testing.T) {
	contracts.TB{Subject: func(tb testing.TB) testcase.TBRunner { return MyTestRunner{TB: tb} }}.Test(t)
}

type Var added in v0.16.0 

type Var[V any] struct {
	// ID is the testCase spec variable group from where the cached value can be accessed later on.
	// ID is Mandatory when you create a variable, else the empty string will be used as the variable group.
	ID string
	// Init is an optional constructor definition that will be used when Var is bonded to a *Spec without constructor function passed to the Let function.
	// The goal of this field to initialize a variable that can be reused across different testing suites by bounding the Var to a given testing suite.
	//
	// Please use #Get if you wish to access a testCase runtime across cached variable value.
	// The value returned by this is not subject to any #Before and #Around hook that might mutate the variable value during the testCase runtime.
	// Init function doesn't cache the value in the testCase runtime spec but literally just meant to initialize a value for the Var in a given test case.
	// Please use it with caution.
	Init VarInit[V]
	// Before is a hook that will be executed once during the lifetime of tests that uses the Var.
	// If the Var is not bound to the Spec at Spec.Context level, the Before Hook will be executed at Var.Get.
	Before func(t *T, v Var[V])
	// OnLet is an optional Var hook that is executed when the variable being bind to Spec context.
	// This hook is ideal to set up tags on the Spec, call Spec.Sequential
	// or ensure binding of further dependencies that this variable requires.
	//
	// In case OnLet is provided, the Var must be explicitly set to a Spec with a Let call
	// else accessing the Var value will panic and warn about this.
	OnLet func(s *Spec, v Var[V])
}

Var is a testCase helper structure, that allows easy way to access testCase runtime variables. In the future it will be updated to use Go2 type parameters.

Var allows creating testCase variables in a modular way. By modular, imagine that you can have commonly used values initialized and then access it from the testCase runtime spec. This approach allows an easy dependency injection maintenance at project level for your testing suite. It also allows you to have parallel testCase execution where you don't expect side effect from your subject. 

e.g.: HTTP JSON API testCase and GraphQL testCase both use the business rule instances.
Or multiple business rules use the same storage dependency.

The last use-case it allows is to define dependencies for your testCase subject before actually assigning values to it. Then you can focus on building up the testing spec and assign values to the variables at the right testing subcontext. With variables, it is easy to forget to assign a value to a variable or forgot to clean up the value of the previous run and then scratch the head during debugging. If you forgot to set a value to the variable in testcase, it warns you that this value is not yet defined to the current testing scope.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
	"github.com/adamluzsi/testcase/internal/example/memory"
	"github.com/adamluzsi/testcase/internal/example/mydomain"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	var (
		storage = testcase.Let[mydomain.Storage](s, func(t *testcase.T) mydomain.Storage {
			return memory.NewStorage()
		})
		subject = testcase.Let(s, func(t *testcase.T) *mydomain.MyUseCase {
			return &mydomain.MyUseCase{Storage: storage.Get(t)}
		})
	)

	s.Describe(`#MyFunc`, func(s *testcase.Spec) {
		var subject = func(t *testcase.T) {
			// after GO2 this will be replaced with concrete Types instead of interface{}
			subject.Get(t).MyFunc()
		}

		s.Then(`do some testCase`, func(t *testcase.T) {
			subject(t) // act
			// assertions here.
		})

		// ...
		// other cases with resource xy state change
	})
}

Output:
Example (Before) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)
	v := testcase.Var[int]{
		ID:   "myvar",
		Init: func(t *testcase.T) int { return 42 },
		Before: func(t *testcase.T, v testcase.Var[int]) {
			t.Logf(`I'm from the Var.Before block, and the value: %#v`, v.Get(t))
		},
	}
	s.Test(``, func(t *testcase.T) {
		_ = v.Get(t)
		// log: I'm from the Var.Before block
		// -> 42
	})
}

Output:
Example (Init) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)

	value := testcase.Var[int]{
		ID: `value`,
		Init: func(t *testcase.T) int {
			return 42
		},
	}

	s.Test(`some testCase`, func(t *testcase.T) {
		_ = value.Get(t) // 42
	})
}

Output:
Example (OnLet) 
package main

import (
	"database/sql"
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	// package spechelper
	var db = testcase.Var[*sql.DB]{
		ID: `db`,
		Init: func(t *testcase.T) *sql.DB {
			db, err := sql.Open(`driver`, `dataSourceName`)
			if err != nil {
				t.Fatal(err.Error())
			}
			return db
		},
		OnLet: func(s *testcase.Spec, _ testcase.Var[*sql.DB]) {
			s.Tag(`database`)
			s.Sequential()
		},
	}

	var tb testing.TB
	s := testcase.NewSpec(tb)
	db.Let(s, nil)
	s.Test(`some testCase`, func(t *testcase.T) {
		_ = db.Get(t)
		t.HasTag(`database`) // true
	})
}

Output:

func Let added in v0.66.0 

func Let[V any](spec *Spec, blk VarInit[V]) Var[V]

Let define a memoized helper method. Let creates lazily-evaluated test execution bound variables. Let variables don't exist until called into existence by the actual tests, so you won't waste time loading them for examples that don't use them. They're also memoized, so they're useful for encapsulating database objects, due to the cost of making a database request. The value will be cached across list use within the same test execution but not across different test cases. You can eager load a value defined in let by referencing to it in a Before hook. Let is threadsafe, the parallel running test will receive they own test variable instance.

Defining a value in a spec Context will ensure that the scope and it's nested scopes of the current scope will have access to the value. It cannot leak its value outside from the current scope. Calling Let in a nested/sub scope will apply the new value for that value to that scope and below.

It will panic if it is used after a When/And/Then scope definition, because those scopes would have no clue about the later defined variable. In order to keep the specification reading mental model requirement low, it is intentionally not implemented to handle such case. Defining test vars always expected in the beginning of a specification scope, mainly for readability reasons.

vars strictly belong to a given `Describe`/`When`/`And` scope, and configured before any hook would be applied, therefore hooks always receive the most latest version from the `Let` vars, regardless in which scope the hook that use the variable is define.

Let can enhance readability when used sparingly in any given example group, but that can quickly degrade with heavy overuse.

func LetValue added in v0.66.0 

func LetValue[V any](spec *Spec, value V) Var[V]

LetValue is a shorthand for defining immutable vars with Let under the hood. So the function blocks can be skipped, which makes tests more readable.

func (Var[V]) Bind added in v0.56.0 

func (v Var[V]) Bind(s *Spec) Var[V]

Bind is a syntax sugar shorthand for Var.Let(*Spec, nil), where skipping providing a block meant to be explicitly expressed.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)
	v := testcase.Var[int]{ID: "myvar", Init: func(t *testcase.T) int { return 42 }}
	v.Bind(s)
	s.Test(``, func(t *testcase.T) {
		_ = v.Get(t) // -> 42
	})
}

Output:

func (Var[V]) EagerLoading added in v0.16.0 

func (v Var[V]) EagerLoading(s *Spec) Var[V]

EagerLoading allows the variable to be loaded before the action and assertion block is reached. This can be useful when you want to have a variable that cause side effect on your system. Like it should be present in some sort of attached resource/storage.

For example, you may persist the value in a storage as part of the initialization block, and then when the testCase/then block is reached, the entity is already present in the resource.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	value := testcase.Let(s, func(t *testcase.T) interface{} {
		return 42
	})

	// will be loaded early on, before the test case block reached.
	// This can be useful when you want to have variables,
	// that also must be present in some sort of attached resource,
	// and as part of the constructor, you want to save it.
	// So when the testCase block is reached, the entity is already present in the resource.
	value.EagerLoading(s)

	s.Test(`some testCase`, func(t *testcase.T) {
		_ = value.Get(t) // -> 42
		// value returned from cache instead of triggering first time initialization.
	})
}

Output:

func (Var[V]) Get added in v0.16.0 

func (v Var[V]) Get(t *T) V

Get returns the current cached value of the given Variable Get is a thread safe operation. When Go2 released, it will replace type casting

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	value := testcase.Let(s, func(t *testcase.T) interface{} {
		return 42
	})

	s.Test(`some testCase`, func(t *testcase.T) {
		_ = value.Get(t) // -> 42
	})
}

Output:

func (Var[V]) Let added in v0.16.0 

func (v Var[V]) Let(s *Spec, blk VarInit[V]) Var[V]

Let allow you to set the variable value to a given spec

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	value := testcase.Var[int]{
		ID: `the variable group`,
		Init: func(t *testcase.T) int {
			return 42
		},
	}

	value.Let(s, nil)

	s.Test(`some testCase`, func(t *testcase.T) {
		_ = value.Get(t) // -> 42
	})
}

Output:
Example (EagerLoading) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	value := testcase.Var[int]{ID: `value`}

	value.Let(s, func(t *testcase.T) int {
		return 42
	}).EagerLoading(s)

	s.Test(`some testCase`, func(t *testcase.T) {
		_ = value.Get(t) // -> 42
		// value returned from cache instead of triggering first time initialization.
	})
}

Output:
Example (ValueDefinedAtTestingContextScope) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	value := testcase.Var[int]{ID: `the variable group`}

	value.Let(s, func(t *testcase.T) int {
		return 42
	})

	s.Test(`some testCase`, func(t *testcase.T) {
		_ = value.Get(t) // -> 42
	})
}

Output:

func (Var[V]) LetValue added in v0.16.0 

func (v Var[V]) LetValue(s *Spec, value V) Var[V]

LetValue set the value of the variable to a given block

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	value := testcase.Var[int]{ID: `the variable group`}

	value.LetValue(s, 42)

	s.Test(`some testCase`, func(t *testcase.T) {
		_ = value.Get(t) // -> 42
	})
}

Output:
Example (EagerLoading) 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	value := testcase.Var[int]{ID: `value`}
	value.LetValue(s, 42).EagerLoading(s)

	s.Test(`some testCase`, func(t *testcase.T) {
		_ = value.Get(t) // -> 42
		// value returned from cache instead of triggering first time initialization.
	})
}

Output:

func (Var[V]) PreviousValue added in v0.103.1 

func (v Var[V]) PreviousValue(t *T) V

PreviousValue is a syntax sugar for Var.Super to access the previous declaration's value.

func (Var[V]) Set added in v0.16.0 

func (v Var[V]) Set(t *T, value V)

Set sets a value to a given variable during testCase runtime Set is a thread safe operation.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var t *testing.T
	s := testcase.NewSpec(t)

	value := testcase.Let(s, func(t *testcase.T) interface{} {
		return 42
	})

	s.Before(func(t *testcase.T) {
		value.Set(t, 24)
	})

	s.Test(`some testCase`, func(t *testcase.T) {
		_ = value.Get(t) // -> 24
	})
}

Output:

func (Var[V]) Super added in v0.103.0 

func (v Var[V]) Super(t *T) V

Super will return the inherited Super value of your Var. This means that if you declared Var in an outer Spec.Context, or your Var has an Var.Init field, then Var.Super will return its content. This allows you to incrementally extend with values the inherited value until you reach your testing scope. This also allows you to wrap your Super value with a Spy or Stub wrapping layer, and pry the interactions with the object while using the original value as a base.

Example 
package main

import (
	"testing"

	"github.com/adamluzsi/testcase"
)

func main() {
	var tb testing.TB
	s := testcase.NewSpec(tb)

	v := testcase.Let[int](s, func(t *testcase.T) int {
		return 32
	})

	s.Context("some sub context", func(s *testcase.Spec) {
		v.Let(s, func(t *testcase.T) int {
			return v.Super(t) + 10 // where super == 32 from the parent context
		})

		s.Test("the result of the V", func(t *testcase.T) {
			t.Must.Equal(42, v.Get(t))
		})
	})
}

Output:

type VarInit added in v0.111.1 

type VarInit[V any] func(*T) V

type VarInitFunc added in v0.84.0 

type VarInitFunc[V any] func(*T) V

VarInitFunc is a backward compatibility type for VarInit.

DEPRECATED: use VarInit type instead.

type Waiter added in v0.15.0 

type Waiter = assert.Waiter

Waiter

DEPRECATED: use assert.Waiter instead

Source Files

View all Source files

Directories

Path Synopsis
internal
timecop
docs
examples
examples/header
examples/role
fihttp
caller
doubles
env
example/memory
example/mydomain
example/someextres
example/spechelper
fmterror
reflects
spechelper
teardown
Package let contains Common Testcase Variable Let declarations for testing purpose.
 Package let contains Common Testcase Variable Let declarations for testing purpose.
internal
sextype

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