Help us shape the future of Go! Take the 2026 Go Developer Survey

Why Go
- Case Studies
  
  Common problems companies solve with Go
- Use Cases
  
  Stories about how and why companies use Go
- Security
  
  How Go can help keep you secure by default
Learn
Docs
- Effective Go
  
  Tips for writing clear, performant, and idiomatic Go code
- Go User Manual
  
  A complete introduction to building software with Go
- Standard library
  
  Reference documentation for Go's standard library
- Release Notes
  
  Learn what's new in each Go release
- API
  
  Reference documentation for the pkg.go.dev API
Packages
Community
- Recorded Talks
  
  Videos from prior events
- Meetups
  
  Meet other local Go developers
- Conferences
  
  Learn and network with Go developers from around the world
- Go blog
  
  The Go project's official blog.
- Go project
  
  Get help and stay informed from Go
- Get connected

vlatte

package module

Go to main page

Versions in this module

v1

v1.1.0

Oct 30, 2026

Changes in this version

+ var ErrDelayNotDescribed = errors.New("delay: a function cannot be described as a mock file")

type Delay

+ func LogNormalDistribution(median time.Duration, sigma float64, maxValue time.Duration) Delay

+ Next func(ctx context.Context) (time.Duration, error)

+ type DelayFunc func(context.Context) (time.Duration, error)

+ func (f DelayFunc) Describe() Descriptor

+ func (f DelayFunc) Next(ctx context.Context) (time.Duration, error)

v1.0.0

Oct 30, 2026

Changes in this version

+ const FailureMatch

+ const FailureNoMatch

+ const FailurePanic

+ const FailureReply

+ const HeaderFailure

+ const HeaderMatchedMockHits

+ const HeaderMatchedMockID

+ const HeaderMatchedMockName

+ const HeaderMatchedMockSource

+ const HeaderProxied

+ const HeaderRequestID

+ const LogLevelDebug

+ const LogLevelDisabled

+ const LogLevelError

+ const LogLevelInfo

+ const LogLevelNone

+ const LogLevelWarn

+ var ErrAbort = errors.New("flow: aborted")

+ var ErrDescriptorKeyAlreadyExists = errors.New("descriptor: key already exists")

+ var ErrDescriptorKeyEmpty = errors.New("descriptor: key is empty")

+ var ErrDescriptorSpecNotValidType = errors.New("descriptor: spec is not a valid type")

+ var ErrDuplicateID = errors.New("store: mock id already in use")

+ var ErrEventAlreadyRegistered = errors.New("vlatte: event already registered")

+ var ErrKVKeyNotFound = errors.New("kv: key not found")

+ var ErrMatchPanicked = errors.New("mock: panic")

+ var ErrMatching = errors.New("mock: matching")

+ var ErrNotFound = errors.New("store: mock not found")

+ var ErrNotRecording = errors.New("recorder: not recording")

+ var ErrOutboundRefused = errors.New("server: the address is refused by the outbound rules")

+ var ErrRecording = errors.New("recorder: already recording")

+ var ErrReset = errors.New("flow: reset")

+ var ErrStarted = errors.New("server: already started")

+ var ErrTemplateDataKeyExists = errors.New("server: two template data providers have the same key")

+ func CheckTemplateDataProviders[In any](providers []TemplateDataProvider[In]) error

+ func NotCalled[M Mock](t TestingT, inspector Inspector[M]) bool

+ func ProvideTemplateData[In any](providers []TemplateDataProvider[In], in In) (map[string]any, error)

+ func Times[M Mock](t TestingT, inspector Inspector[M], expected int64) bool

+ type Base struct

+ func NewBase[TM Mock, A any](app A, repo Store[TM]) *Base[TM, A]

+ func (app *Base[TM, A]) AssertCalled(t TestingT) bool

+ func (app *Base[TM, A]) AssertNotCalled(t TestingT) bool

+ func (app *Base[TM, A]) AssertNumberOfCalls(t TestingT, expected int64) bool

+ func (app *Base[TM, A]) Clean(ctx context.Context) error

+ func (app *Base[TM, A]) Disable()

+ func (app *Base[TM, A]) Enable()

+ func (app *Base[TM, A]) Hits() int64

+ func (app *Base[TM, A]) ListCalled() []TM

+ func (app *Base[TM, A]) ListPending() []TM

+ func (app *Base[TM, A]) Mock(builders ...Builder[TM, A]) (*Scope[TM], error)

+ func (app *Base[TM, A]) MustMock(builders ...Builder[TM, A]) *Scope[TM]

+ func (app *Base[TM, A]) Remock(ctx context.Context, old *Scope[TM], builders ...Builder[TM, A]) (*Scope[TM], error)

+ func (app *Base[TM, A]) RemockWith(ctx context.Context, old *Scope[TM], swap Swap[TM], builders ...Builder[TM, A]) (*Scope[TM], error)

+ func (app *Base[TM, A]) Unmock(ctx context.Context, scope *Scope[TM]) error

+ type Builder interface

+ Build func(app TMockApp) (B, error)

+ type Claimer interface

+ Claim func(arg MatcherArg) bool

+ type CleanupT interface

+ Cleanup func(func())

+ type Configurer interface

+ Apply func(conf TConfig) error

+ type Delay func() time.Duration

+ func Jitter(avg time.Duration, deviation float64) Delay

+ func Latency(latency time.Duration) Delay

+ func UniformDistribution(minMillis, maxMillis int64) Delay

+ type Descriptor struct

+ Key string

+ Props DescriptorProps

+ func DescribeFail(key string, err error) Descriptor

+ func DescribeKeyOnly(key string) Descriptor

+ func DescribeKeyOnlyMaybe(key string, item any) Descriptor

+ func DescribeKeyValuePairs(key string, props ...any) Descriptor

+ func DescribeMaybeItems(key string, items []any) Descriptor

+ func DescribeMultiArgs(key string, props ...any) Descriptor

+ func DescribeRoot[T DescriptorPropsType](props T) Descriptor

+ func DescribeSingleArg(key string, item any) Descriptor

+ func IsSelfDescriptive(v any) (Descriptor, bool)

+ func NewDescriptor[T DescriptorPropsType](key string, props T) Descriptor

+ func (d Descriptor) Err() error

+ func (d Descriptor) IsArray() bool

+ func (d Descriptor) IsMap() bool

+ func (d Descriptor) MarshalJSON() ([]byte, error)

+ func (d Descriptor) Marshallable() (any, error)

+ func (d Descriptor) Merge(m map[string]any) error

+ func (d Descriptor) String() string

+ func (d Descriptor) Validate() error

+ type DescriptorProps any

+ type DescriptorPropsType interface

+ type Eval struct

+ Key string

+ Matcher Matcher

+ Selector Selector[TIn]

+ Target int

+ func (e *Eval[TIn]) Arg(ctx context.Context, sub *Explanation, in TIn) MatcherArg

+ func (e *Eval[TIn]) Match(ctx context.Context, sub *Explanation, in TIn) (ok bool, err error)

+ func (e *Eval[TIn]) String() string

+ type Evaluators []*Eval[TIn]

+ func (e Evaluators[M, TIn]) Eval(ctx context.Context, sub *Explanation, in TIn) (bool, error)

+ type EventArgs interface

+ Kind func() Kind

+ Kit func() Kit

+ Parameters func() Parameters

+ type EventConfig struct

+ AfterResponse bool

+ Dir string

+ Listener EventListener[OnComplete]

+ Name string

+ Parameters Parameters

+ type EventConfigs []EventConfig

+ func (e EventConfigs) Has(name string) bool

+ type EventFunc func(ctx context.Context, args T) error

+ func (f EventFunc[T]) Run(ctx context.Context, args T) error

+ type EventListener interface

+ Run func(ctx context.Context, args T) error

+ type EventPreparer interface

+ Prepare func(cfg EventConfig, engine TemplateEngine) (Parameters, error)

+ type EventRegistry struct

+ func NewEventRegistry[T EventArgs]() *EventRegistry[T]

+ func (r *EventRegistry[T]) Has(name string) bool

+ func (r *EventRegistry[T]) Prepare(cfg EventConfig, engine TemplateEngine) (Parameters, error)

+ func (r *EventRegistry[T]) Register(name string, evt EventListener[T]) error

+ func (r *EventRegistry[T]) Run(ctx context.Context, name string, args T) error

+ type EventRunner struct

+ Global *Events

+ Listeners *Listener

+ func NewEventRunner(listeners *Listener, global *Events) *EventRunner

+ func (r *EventRunner) Close()

+ func (r *EventRunner) OnComplete(ctx context.Context, mock Mock, ...)

+ type Events struct

+ OnComplete EventConfigs

+ type Explanation struct

+ Children []*Explanation

+ Items []ExplanationItem

+ Name string

+ Parent *Explanation

+ func NewExplanation() *Explanation

+ func (e *Explanation) AddMessage(message string)

+ func (e *Explanation) Root() bool

+ func (e *Explanation) Sub(name string) *Explanation

+ type ExplanationItem struct

+ Message string

+ type Flow struct

+ func NewFlow(ctx context.Context, sink Stage, pipes []Pipe) *Flow

+ func (f *Flow) Abort(err error)

+ func (f *Flow) Close() error

+ func (f *Flow) Context() context.Context

+ func (f *Flow) Flush() error

+ func (f *Flow) Write(b []byte) (int, error)

+ type GetEvals func(m M) Evaluators[M, TIn]

+ type GoTemplateEngine struct

+ func MustNewGoTemplateEngine(opts ...GoTemplateOption) *GoTemplateEngine

+ func NewGoTemplateEngine(opts ...GoTemplateOption) (*GoTemplateEngine, error)

+ func (e *GoTemplateEngine) Compile(name, text string) (Template, error)

+ type GoTemplateOption func(*GoTemplateEngine) error

+ func WithEnv(names ...string) GoTemplateOption

+ func WithMissingKey(mode string) GoTemplateOption

+ func WithSigningKey(kid, alg string, key crypto.Signer) GoTemplateOption

+ func WithTemplateFuncs(funcs map[string]any) GoTemplateOption

+ type Inspector interface

+ Hits func() int64

+ ListCalled func() []M

+ ListPending func() []M

+ type KV interface

+ Del func(ctx context.Context, k string) error

+ Get func(ctx context.Context, k string) ([]byte, error)

+ Has func(ctx context.Context, k string) (bool, error)

+ Keys func(ctx context.Context) ([]string, error)

+ Set func(ctx context.Context, k string, v []byte) error

+ func NewMemoryKV() KV

+ type KVReloader interface

+ Reload func(ctx context.Context) error

+ func MustNewCSVKV(path string) KVReloader

+ func NewCSVKV(path string) (KVReloader, error)

+ type Kind string

+ func (k Kind) String() string

+ type Kit interface

+ Data func() any

+ Dir func() string

+ Logger func() *zerolog.Logger

+ TemplateEngine func() TemplateEngine

+ Transport func() http.RoundTripper

+ type Listener struct

+ OnComplete *EventRegistry[OnComplete]

+ func NewListener() *Listener

+ type LogLevel = int8

+ type LogVerbosity int8

+ const LogBasic

+ const LogBody

+ const LogHeader

+ func (l LogVerbosity) String() string

+ type Matcher interface

+ Match func(arg MatcherArg) (bool, error)

+ Name func() string

+ func MatcherFunc(name string, fn func(arg MatcherArg) (bool, error)) Matcher

+ type MatcherArg struct

+ func NewMatcherArg(ctx context.Context, exp *Explanation, v any) MatcherArg

+ func (a *MatcherArg) Context() context.Context

+ func (a *MatcherArg) Explain() *Explanation

+ func (a *MatcherArg) Mock() Mock

+ func (a *MatcherArg) Value() any

+ type MemoryStore struct

+ func (s *MemoryStore[B]) Clear(_ context.Context) error

+ func (s *MemoryStore[B]) Delete(_ context.Context, ids ...string) error

+ func (s *MemoryStore[B]) Health(context.Context) error

+ func (s *MemoryStore[B]) List(ctx context.Context) (iter.Seq[B], error)

+ func (s *MemoryStore[B]) Pick(_ context.Context, id string) (B, error)

+ func (s *MemoryStore[B]) PickAll(_ context.Context) ([]B, error)

+ func (s *MemoryStore[B]) Replace(_ context.Context, old []B, mocks ...B) error

+ func (s *MemoryStore[B]) Store(_ context.Context, mocks ...B) error

+ type Misses struct

+ func (m *Misses[M, TIn]) NearMisses(ctx context.Context, describe func(*Eval[TIn]) string) []NearMiss

+ func (m *Misses[M, TIn]) Reset()

+ type Mock interface

+ Called func() bool

+ Disable func()

+ Enable func()

+ Enabled func() bool

+ Events func() Events

+ Hits func() int64

+ ID func() string

+ Name func() string

+ Priority func() int

+ String func() string

+ type MockBuilder interface

+ BuildFromBytes func(content []byte, extension string) (B, error)

+ type MockBuilderFunc func(content []byte, extension string) (B, error)

+ func (f MockBuilderFunc[B]) BuildFromBytes(content []byte, extension string) (B, error)

+ type Mocks iter.Seq[M]

+ func (mocks Mocks[M, TIn]) Find(ctx context.Context, sub *Explanation, in TIn, evals GetEvals[M, TIn], ...) (M, bool, error)

+ type NearMiss struct

+ Failed []string

+ MockID string

+ Name string

+ Passed int

+ Skipped []string

+ Total int

+ type OnComplete interface

+ Mock func() Mock

+ type Parameters any

+ type Pipe interface

+ Open func(flow *Flow, next Stage) Stage

+ type PipeFunc func(ctx context.Context, b []byte, next Stage) (n int, err error)

+ func (f PipeFunc) Open(flow *Flow, next Stage) Stage

+ type Recipe interface

+ Prep func(ctx context.Context, input *RecipeInput[B, A]) error

+ type RecipeFunc func(ctx context.Context, input *RecipeInput[B, A]) error

+ func (f RecipeFunc[B, A]) Prep(ctx context.Context, input *RecipeInput[B, A]) error

+ type RecipeInput struct

+ Server Server[B, A]

+ type RecordBody struct

+ func (b *RecordBody) Bytes() ([]byte, bool)

+ func (b *RecordBody) Close()

+ func (b *RecordBody) Discard()

+ func (b *RecordBody) Err() error

+ func (b *RecordBody) Keep(p []byte)

+ func (b *RecordBody) Len() int64

+ type RecordCodec interface

+ Mock func(m *RecordedMock[Q, S]) any

+ Name func(x X) string

+ Request func(x X, files *RecordFiles) (Q, error)

+ Response func(x X, files *RecordFiles) (S, error)

+ type RecordFiles struct

+ func (f *RecordFiles) Place(body []byte, text bool, ext string) (name string, inline bool)

+ func (f *RecordFiles) PlaceSpooled(b *RecordBody, ext string) (string, error)

+ type RecordOptions struct

+ BodyFiles bool

+ Dir string

+ Format string

+ Logger *zerolog.Logger

+ MaxBodySize int64

+ MaxInlineBody int64

+ Repeats RecordRepeats

+ Transforms []func(*RecordedMock[Q, S]) error

+ type RecordRepeats int

+ const RecordFirst

+ const RecordSequence

+ type RecordResult struct

+ Recordings []Recording

+ Status RecordStatus

+ type RecordSession struct

+ func MustNewRecordSession[X, Q, S any](c RecordCodec[X, Q, S], o RecordOptions[Q, S]) *RecordSession[X, Q, S]

+ func NewRecordSession[X, Q, S any](c RecordCodec[X, Q, S], o RecordOptions[Q, S]) (*RecordSession[X, Q, S], error)

+ func (s *RecordSession[X, Q, S]) Done() <-chan struct{}

+ func (s *RecordSession[X, Q, S]) NewBody() *RecordBody

+ func (s *RecordSession[X, Q, S]) Record(x X, size int) bool

+ func (s *RecordSession[X, Q, S]) Status() RecordStatus

+ func (s *RecordSession[X, Q, S]) Stop(ctx context.Context) (*RecordResult, error)

+ type RecordStatus struct

+ Active bool

+ Calls int64

+ Dropped int64

+ Failed int64

+ Mocks int64

+ type RecordedMock struct

+ ID string

+ Name string

+ Request Q

+ Responses []S

+ type Recording struct

+ BodyFiles []string

+ File string

+ ID string

+ Name string

+ Responses int

+ type Replier interface

+ Reply func(ctx context.Context, input I) (R, error)

+ type ReplierFactory interface

+ NewReplier func(app A) (Replier[I, R], error)

+ type Scope struct

+ func NewScope[B Mock](mocks []B, store Store[B]) *Scope[B]

+ func (s *Scope[B]) AssertCalled(t TestingT) bool

+ func (s *Scope[B]) AssertNotCalled(t TestingT) bool

+ func (s *Scope[B]) AssertNumberOfCalls(t TestingT, expected int64) bool

+ func (s *Scope[B]) Called() bool

+ func (s *Scope[B]) Clear(ctx context.Context) error

+ func (s *Scope[B]) Delete(ctx context.Context, ids ...string) error

+ func (s *Scope[B]) Disable()

+ func (s *Scope[B]) Enable()

+ func (s *Scope[B]) Exists(id string) bool

+ func (s *Scope[B]) Hits() int64

+ func (s *Scope[B]) IDs() []string

+ func (s *Scope[B]) ListCalled() []B

+ func (s *Scope[B]) ListPending() []B

+ func (s *Scope[B]) Mock(id string) B

+ func (s *Scope[B]) Mocks() []B

+ func (s *Scope[B]) Pending() bool

+ type Scopes struct

+ func (s *Scopes[B, A]) Add(builders ...Builder[B, A]) (*Scope[B], error)

+ func (s *Scopes[B, A]) All() []*Scope[B]

+ func (s *Scopes[B, A]) Remove(ctx context.Context, scope *Scope[B]) error

+ func (s *Scopes[B, A]) Replace(ctx context.Context, old *Scope[B], builders ...Builder[B, A]) (*Scope[B], error)

+ type Selector func(ctx context.Context, input TIn) any

+ type SelfDescriptive interface

+ Describe func() Descriptor

+ type Server interface

+ Clean func(ctx context.Context) error

+ Disable func()

+ Enable func()

+ Hits func() int64

+ Mock func(builders ...Builder[B, A]) (*Scope[B], error)

+ type Sink struct

+ W io.Writer

+ func (s *Sink) Close() error

+ func (s *Sink) Flush() error

+ func (s *Sink) Write(p []byte) (n int, err error)

+ type Stage interface

+ Close func() error

+ Flush func() error

+ Write func(b []byte) (n int, err error)

+ type Stateful interface

+ SetState func() error

+ type Store interface

+ Clear func(ctx context.Context) error

+ Delete func(ctx context.Context, ids ...string) error

+ Health func(ctx context.Context) error

+ List func(ctx context.Context) (iter.Seq[T], error)

+ Pick func(ctx context.Context, id string) (T, error)

+ PickAll func(ctx context.Context) ([]T, error)

+ Replace func(ctx context.Context, old []T, mocks ...T) error

+ Store func(ctx context.Context, mocks ...T) error

+ func NewStore[B Mock]() Store[B]

+ type Swap func(built, gone []TM) (drop, add []TM, err error)

+ type Template interface

+ Execute func(w io.Writer, data any) error

+ type TemplateDataProvider interface

+ Data func(in In) (any, error)

+ Key func() string

+ type TemplateEngine interface

+ Compile func(name, text string) (Template, error)

+ type TestingT interface

+ Error func(a ...any)

+ Errorf func(format string, a ...any)

+ Helper func()

+ Logf func(format string, a ...any)

v0

v0.1.0-rc.1

Oct 28, 2026