package standard library
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Published: Jul 2, 2024 License: BSD-3-Clause Imports: 7 Imported by: 325



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

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



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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 {

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.


type CheckEqualError

type CheckEqualError struct {
	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

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