How to correctly implement gomock InOrder for mock calls?

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1

I’m using the gomock package in a Go project, running on Linux with Go 1.18. My goal is to ensure that mock method calls occur in a specific sequence using the InOrder method. I’ve attempted to set it up in my tests, but I’m not seeing the expected order enforcement. Instead, the methods seem to execute in any order without errors. What steps can I take to enforce the correct order of calls using gomock InOrder?

2

This problem sounds familiar, I’ve run into it myself when setting up mock calls with InOrder. Typically, this issue happens when the expectations aren’t applied correctly in sequence, which is crucial for gomock to enforce order.

In gomock, the InOrder method allows you to specify that certain mock expectations must be fulfilled in the sequence they’re defined. If the calls arrive in the wrong order, the test will fail. It’s important to enforce strict expectations using the InOrder method, ensuring that you wrap your expected calls inside it.

Here is the snippet that worked for me:

mockCtrl := gomock.NewController(t)
defer mockCtrl.Finish()
mockObj := NewMockYourInterface(mockCtrl)

gomock.InOrder(
    mockObj.EXPECT().FirstMethod().Return(nil),
    mockObj.EXPECT().SecondMethod().Return(nil),
)

// Call the methods in the correct order
mockObj.FirstMethod()
mockObj.SecondMethod()

This code creates a new mock controller and defines expectations for mockObj methods FirstMethod and SecondMethod, enforcing order. Both methods need to be called exactly in the defined sequence during your test.

Remember to structure the actual method calls in the test to match the defined sequence, and always call mockCtrl.Finish() to verify the call expectations. If any deviations occur, gomock will provide a detailed error message, helping you pinpoint the source of the problem.

3

I’ve been there, and it’s pretty common to initially set up InOrder incorrectly or miss a crucial detail. In one of my recent projects, I realized my mistake was assuming InOrder was applied outside the closure of expected calls.

When applying InOrder, it’s necessary to encapsulate all your expected calls inside the gomock.InOrder function. If even one call isn’t properly wrapped, gomock won’t enforce the order, leading to potential chaos in method execution. Double check the placement inside your test suite to avoid mismatches.

Here’s how I successfully implemented it:

mockCtrl := gomock.NewController(t)
defer mockCtrl.Finish()
mockObj := NewMockMyInterface(mockCtrl)

callOrder := gomock.InOrder(
    mockObj.EXPECT().Read().Return(data, nil),
    mockObj.EXPECT().Process().Return(nil),
)

mockObj.Read()
mockObj.Process()

Notice that each expectation is confined within the InOrder bracket, which guides gomock to ensure they’re executed accordingly. In my scenario, I adjusted my call logic in the test body to confirm that each call’s setup perfectly mimicked the intended order.

Another common pitfall is neglecting to finalize the mock controller. This step is critical since it signals gomock to verify the correct execution order. Always finalize your controller to catch any deviations, which gomock will flag promptly.