quick

Documentation

Overview

Package quick implements utility functions to help with black box testing.

The testing/quick package is frozen and is not accepting new features.

Index

• func Check(f any, config *Config) error
• func CheckEqual(f, g any, config *Config) error
• func Value(t reflect.Type, rand *rand.Rand) (value reflect.Value, ok bool)
• type CheckEqualError
  • func (s *CheckEqualError) Error() string
• type CheckError
  • func (s *CheckError) Error() string
• type Config
• type Generator
• type SetupError
  • func (s SetupError) Error() string

Functions

func Check

func Check(f any, config *Config) error

Check looks for an input to f, any function that returns bool, such that f returns false. It calls f repeatedly, with arbitrary values for each argument. If f returns false on a given input, Check returns that input as a *CheckError. For example:

func TestOddMultipleOfThree(t *testing.T) {
	f := func(x int) bool {
		y := OddMultipleOfThree(x)
		return y%2 == 1 && y%3 == 0
	}
	if err := quick.Check(f, nil); err != nil {
		t.Error(err)
	}
}

func CheckEqual

func CheckEqual(f, g any, config *Config) error

CheckEqual looks for an input on which f and g return different results. It calls f and g repeatedly with arbitrary values for each argument. If f and g return different answers, CheckEqual returns a *CheckEqualError describing the input and the outputs.

func Value

func Value(t reflect.Type, rand *rand.Rand) (value reflect.Value, ok bool)

Value returns an arbitrary value of the given type. If the type implements the Generator interface, that will be used. Note: To create arbitrary values for structs, all the fields must be exported.

Types

type CheckEqualError

type CheckEqualError struct {
	CheckError
	Out1 []any
	Out2 []any
}

A CheckEqualError is the result CheckEqual finding an error.

func (*CheckEqualError) Error

func (s *CheckEqualError) Error() string

type CheckError

type CheckError struct {
	Count int
	In    []any
}

A CheckError is the result of Check finding an error.

func (*CheckError) Error

func (s *CheckError) Error() string

type Config

type Config struct {
	// MaxCount sets the maximum number of iterations.
	// If zero, MaxCountScale is used.
	MaxCount int
	// MaxCountScale is a non-negative scale factor applied to the
	// default maximum.
	// A count of zero implies the default, which is usually 100
	// but can be set by the -quickchecks flag.
	MaxCountScale float64
	// Rand specifies a source of random numbers.
	// If nil, a default pseudo-random source will be used.
	Rand *rand.Rand
	// Values specifies a function to generate a slice of
	// arbitrary reflect.Values that are congruent with the
	// arguments to the function being tested.
	// If nil, the top-level Value function is used to generate them.
	Values func([]reflect.Value, *rand.Rand)
}

A Config structure contains options for running a test.

type Generator

type Generator interface {
	// Generate returns a random instance of the type on which it is a
	// method using the size as a size hint.
	Generate(rand *rand.Rand, size int) reflect.Value
}

A Generator can generate random values of its own type.

type SetupError

type SetupError string

A SetupError is the result of an error in the way that check is being used, independent of the functions being tested.

func (SetupError) Error

func (s SetupError) Error() string