Add Mock#Reset()

[jonnyreeves]

Provide a methods for clearing all programed expectations from a mock; useful during a TestSuite tear-down method to ensure you have a clean slate between test-runs.

[codeactual]

Should all Calls and testData also be reset to fully clear the slate?

[ernesto-jimenez]

@jonnyreeves could you provide an example on how you would use it?

I would like to understand the use case better :)

[jimmiebtlr]

I'll hop in with my use case.

I start a router with a passed in DB, and potentially some others. I'd like to reset the db mock between tests without needing to stop and start the server.

So pretty much any case where something can be resource or time intensive to start and stop, that you want to test with a mock.

[ernesto-jimenez]

@jimmiebtlr you can already do that as follows:

// mock
type myMock struct {
    mock.Mock
}
// initialise
m := &myMock{}
// [...]
// Reset
m.Mock = mock.Mock{}

Have you ever used this?

[jimmiebtlr]

Oh, sweet, didn't realize you could do that.

[Monnoroch]

I have another use case. Here's a component:

type StuffDoer struct {
    HelpfulDependency HelpfulInterface
}

func (self *StuffDoer) DoStuff() string {
    ...
}

Of course I want to test it. I have test suit with one test per feature for the DoStuff method. Most tests want self.HelpfulDependency.On("HelpfulMethod").Return(result1), but I have a single test that wants self.HelpfulDependency.On("HelpfulMethod").Return(result2). Ideally I set up the default case in the SetupTest() and override it once in the single test that requires a different response. Right now, doing .On() for the second time does not override, so I either have to .Reset() first (which is absent) or recreate the StuffDoer object with the newly created mock. Ideally I would want testify to do what Mockito does: override previous calls with .On(), but .Reset() is an okay alternative.

[daniellowtw]

@ernesto-jimenez I also think abstracting the resetting of mocks can improve readability, and also standardize the ways of doing that. It is also more aligned with the intuition when using the mocks, as suggested in @Monnoroch example.

Using the suite package, it would be nicer to read and easier to understand

func(s *MyTestSuite) SetupTest() {
	s.myMock.Reset()
}

Instead of other possibilities such as

func(s *MyTestSuite) SetupTest() {
	// option 1
	s.myMock.ExpectedCalls = nil
	s.myMock.Calls = nil
}

or

func(s *MyTestSuite) SetupTest() {
	// option 2
	s.myMock.Mock = mock.Mock{}
}

[jvitoroc]

May I suggest a simpler solution that would require a simple modification?
https://github.com/jvitoroc/testify/blob/master/mock/mock.go#L225

func (m *Mock) Reset() {
	*m = Mock{}
}