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Published: Feb 9, 2021 License: Apache-2.0 Imports: 8 Imported by: 0



Package gomock is a mock framework for Go.

Standard usage:

(1) Define an interface that you wish to mock.
      type MyInterface interface {
        SomeMethod(x int64, y string)
(2) Use mockgen to generate a mock from the interface.
(3) Use the mock in a test:
      func TestMyThing(t *testing.T) {
        mockCtrl := gomock.NewController(t)
        defer mockCtrl.Finish()

        mockObj := something.NewMockMyInterface(mockCtrl)
        mockObj.EXPECT().SomeMethod(4, "blah")
        // pass mockObj to a real object and play with it.

By default, expected calls are not enforced to run in any particular order. Call order dependency can be enforced by use of InOrder and/or Call.After. Call.After can create more varied call order dependencies, but InOrder is often more convenient.

The following examples create equivalent call order dependencies.

Example of using Call.After to chain expected call order:

firstCall := mockObj.EXPECT().SomeMethod(1, "first")
secondCall := mockObj.EXPECT().SomeMethod(2, "second").After(firstCall)
mockObj.EXPECT().SomeMethod(3, "third").After(secondCall)

Example of using InOrder to declare expected call order:

    mockObj.EXPECT().SomeMethod(1, "first"),
    mockObj.EXPECT().SomeMethod(2, "second"),
    mockObj.EXPECT().SomeMethod(3, "third"),


  • Handle different argument/return types (e.g. ..., chan, map, interface).



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func InOrder

func InOrder(calls ...*Call)

InOrder declares that the given calls should occur in order.


type Call

type Call struct {
	// contains filtered or unexported fields

Call represents an expected call to a mock.

func (*Call) After

func (c *Call) After(preReq *Call) *Call

After declares that the call may only match after preReq has been exhausted.

func (*Call) AnyTimes

func (c *Call) AnyTimes() *Call

AnyTimes allows the expectation to be called 0 or more times

func (*Call) Do

func (c *Call) Do(f interface{}) *Call

Do declares the action to run when the call is matched. The function's return values are ignored to retain backward compatibility. To use the return values call DoAndReturn. It takes an interface{} argument to support n-arity functions.

func (*Call) DoAndReturn

func (c *Call) DoAndReturn(f interface{}) *Call

DoAndReturn declares the action to run when the call is matched. The return values from this function are returned by the mocked function. It takes an interface{} argument to support n-arity functions.

func (*Call) MaxTimes

func (c *Call) MaxTimes(n int) *Call

MaxTimes limits the number of calls to n times. If AnyTimes or MinTimes have not been called, MaxTimes also sets the minimum number of calls to 0.

func (*Call) MinTimes

func (c *Call) MinTimes(n int) *Call

MinTimes requires the call to occur at least n times. If AnyTimes or MaxTimes have not been called, MinTimes also sets the maximum number of calls to infinity.

func (*Call) Return

func (c *Call) Return(rets ...interface{}) *Call

Return declares the values to be returned by the mocked function call.

func (*Call) SetArg

func (c *Call) SetArg(n int, value interface{}) *Call

SetArg declares an action that will set the nth argument's value, indirected through a pointer. Or, in the case of a slice, SetArg will copy value's elements into the nth argument.

func (*Call) String

func (c *Call) String() string

func (*Call) Times

func (c *Call) Times(n int) *Call

Times declares the exact number of times a function call is expected to be executed.

type Controller

type Controller struct {
	// T should only be called within a generated mock. It is not intended to
	// be used in user code and may be changed in future versions. T is the
	// TestReporter passed in when creating the Controller via NewController.
	// If the TestReporter does not implement a TestHelper it will be wrapped
	// with a nopTestHelper.
	T TestHelper
	// contains filtered or unexported fields

A Controller represents the top-level control of a mock ecosystem. It defines the scope and lifetime of mock objects, as well as their expectations. It is safe to call Controller's methods from multiple goroutines. Each test should create a new Controller and invoke Finish via defer.

func TestFoo(t *testing.T) {
  ctrl := gomock.NewController(st)
  defer ctrl.Finish()
  // ..

func TestBar(t *testing.T) {
  t.Run("Sub-Test-1", st) {
    ctrl := gomock.NewController(st)
    defer ctrl.Finish()
    // ..
  t.Run("Sub-Test-2", st) {
    ctrl := gomock.NewController(st)
    defer ctrl.Finish()
    // ..

func NewController

func NewController(t TestReporter) *Controller

NewController returns a new Controller. It is the preferred way to create a Controller.

func WithContext

func WithContext(ctx context.Context, t TestReporter) (*Controller, context.Context)

WithContext returns a new Controller and a Context, which is cancelled on any fatal failure.

func (*Controller) Call

func (ctrl *Controller) Call(receiver interface{}, method string, args ...interface{}) []interface{}

Call is called by a mock. It should not be called by user code.

func (*Controller) Finish

func (ctrl *Controller) Finish()

Finish checks to see if all the methods that were expected to be called were called. It should be invoked for each Controller. It is not idempotent and therefore can only be invoked once.

func (*Controller) RecordCall

func (ctrl *Controller) RecordCall(receiver interface{}, method string, args ...interface{}) *Call

RecordCall is called by a mock. It should not be called by user code.

func (*Controller) RecordCallWithMethodType

func (ctrl *Controller) RecordCallWithMethodType(receiver interface{}, method string, methodType reflect.Type, args ...interface{}) *Call

RecordCallWithMethodType is called by a mock. It should not be called by user code.

type Matcher

type Matcher interface {
	// Matches returns whether x is a match.
	Matches(x interface{}) bool

	// String describes what the matcher matches.
	String() string

A Matcher is a representation of a class of values. It is used to represent the valid or expected arguments to a mocked method.

func Any

func Any() Matcher

Constructors Any returns a matcher that always matches.

func AssignableToTypeOf

func AssignableToTypeOf(x interface{}) Matcher

AssignableToTypeOf is a Matcher that matches if the parameter to the mock function is assignable to the type of the parameter to this function.

Example usage:

var s fmt.Stringer = &bytes.Buffer{}
AssignableToTypeOf(s).Matches(time.Second) // returns true
AssignableToTypeOf(s).Matches(99) // returns false

func Eq

func Eq(x interface{}) Matcher

Eq returns a matcher that matches on equality.

Example usage:

Eq(5).Matches(5) // returns true
Eq(5).Matches(4) // returns false

func Nil

func Nil() Matcher

Nil returns a matcher that matches if the received value is nil.

Example usage:

var x *bytes.Buffer
Nil().Matches(x) // returns true
x = &bytes.Buffer{}
Nil().Matches(x) // returns false

func Not

func Not(x interface{}) Matcher

Not reverses the results of its given child matcher.

Example usage:

Not(Eq(5)).Matches(4) // returns true
Not(Eq(5)).Matches(5) // returns false

type TestHelper

type TestHelper interface {

TestHelper is a TestReporter that has the Helper method. It is satisfied by the standard library's *testing.T.

type TestReporter

type TestReporter interface {
	Errorf(format string, args ...interface{})
	Fatalf(format string, args ...interface{})

A TestReporter is something that can be used to report test failures. It is satisfied by the standard library's *testing.T.

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