Expect function call order

You can specify the right order of the function calls especially if the order matters. For example, ProcessVideo requires the right steps to process a video. The expected order is enforced by mock.InOrder.

main.go

//go:generate mockery --name=Processor --dir=. --output=./mocks --outpkg=servicemock --case=snake

// ...

type Processor interface {
	Download(ctx context.Context, videoID string) ([]byte, error)
	Compress(ctx context.Context, raw []byte) ([]byte, error)
	Upload(ctx context.Context, videoID string, compressed []byte) error
}

func ProcessVideo(ctx context.Context, p Processor, videoID string) error {
	if videoID == "" {
		return fmt.Errorf("videoID must be non-empty")
	}
	raw, err := p.Download(ctx, videoID)
	if err != nil {
		return err
	}
	compressed, err := p.Compress(ctx, raw)
	if err != nil {
		return err
	}
	return p.Upload(ctx, videoID, compressed)
}

main_test.go

func TestProcessVideo(t *testing.T) {
	ctx := context.Background()

	tests := []struct {
		name       string
		videoID    string
		raw        []byte
		compressed []byte
	}{
		{name: "happy_path", videoID: "vid-123", raw: []byte("raw"), compressed: []byte("c")},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			mockProc := servicemock.NewProcessor(t)

			mock.InOrder(
				mockProc.On("Download", mock.Anything, tt.videoID).Return(tt.raw, nil),
				mockProc.On("Compress", mock.Anything, tt.raw).Return(tt.compressed, nil),
				mockProc.On("Upload", mock.Anything, tt.videoID, tt.compressed).Return(nil),
			)

			err := ProcessVideo(ctx, mockProc, tt.videoID)
			require.NoError(t, err)
		})
	}
}

Mocked service below:

// Code generated by mockery v2.53.5. DO NOT EDIT.

package servicemock

import (
	context "context"

	mock "github.com/stretchr/testify/mock"
)

// Processor is an autogenerated mock type for the Processor type
type Processor struct {
	mock.Mock
}

// Compress provides a mock function with given fields: ctx, raw
func (_m *Processor) Compress(ctx context.Context, raw []byte) ([]byte, error) {
	ret := _m.Called(ctx, raw)

	if len(ret) == 0 {
		panic("no return value specified for Compress")
	}

	var r0 []byte
	var r1 error
	if rf, ok := ret.Get(0).(func(context.Context, []byte) ([]byte, error)); ok {
		return rf(ctx, raw)
	}
	if rf, ok := ret.Get(0).(func(context.Context, []byte) []byte); ok {
		r0 = rf(ctx, raw)
	} else {
		if ret.Get(0) != nil {
			r0 = ret.Get(0).([]byte)
		}
	}

	if rf, ok := ret.Get(1).(func(context.Context, []byte) error); ok {
		r1 = rf(ctx, raw)
	} else {
		r1 = ret.Error(1)
	}

	return r0, r1
}

// Download provides a mock function with given fields: ctx, videoID
func (_m *Processor) Download(ctx context.Context, videoID string) ([]byte, error) {
	ret := _m.Called(ctx, videoID)

	if len(ret) == 0 {
		panic("no return value specified for Download")
	}

	var r0 []byte
	var r1 error
	if rf, ok := ret.Get(0).(func(context.Context, string) ([]byte, error)); ok {
		return rf(ctx, videoID)
	}
	if rf, ok := ret.Get(0).(func(context.Context, string) []byte); ok {
		r0 = rf(ctx, videoID)
	} else {
		if ret.Get(0) != nil {
			r0 = ret.Get(0).([]byte)
		}
	}

	if rf, ok := ret.Get(1).(func(context.Context, string) error); ok {
		r1 = rf(ctx, videoID)
	} else {
		r1 = ret.Error(1)
	}

	return r0, r1
}

// Upload provides a mock function with given fields: ctx, videoID, compressed
func (_m *Processor) Upload(ctx context.Context, videoID string, compressed []byte) error {
	ret := _m.Called(ctx, videoID, compressed)

	if len(ret) == 0 {
		panic("no return value specified for Upload")
	}

	var r0 error
	if rf, ok := ret.Get(0).(func(context.Context, string, []byte) error); ok {
		r0 = rf(ctx, videoID, compressed)
	} else {
		r0 = ret.Error(0)
	}

	return r0
}

// NewProcessor creates a new instance of Processor. It also registers a testing interface on the mock and a cleanup function to assert the mocks expectations.
// The first argument is typically a *testing.T value.
func NewProcessor(t interface {
	mock.TestingT
	Cleanup(func())
}) *Processor {
	mock := &Processor{}
	mock.Mock.Test(t)

	t.Cleanup(func() { mock.AssertExpectations(t) })

	return mock
}