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使用gomock时可以调用EXPECT()为你的mock对象设置各种期望和返回值，用于验证期望值和运行时的值是否一致。通常情况下可以通过gomock来清晰的看出期望值和真实值的区别，但是当数据结构为指针切片时就只能看到下面这种提示，不能清晰的看出二者的区别是什么。
Got: [0xc000060610] ([]*demo.Item)Want: is equal to [0xc0000605b0] ([]*demo.Item)
可以通过设置 gomock Modifying Failure Messages的能力来优化这一点，举例如下。
// 优化前错误日志如下, 此时只能看到数据有 diff， 但不知道是什么//--- FAIL: TestSaveToFile (1.00s)// demo/demo.go:12: Unexpected call to *demo.MockSaver.Save([[0xc000060610]]) at demo/demo.go:12 because: // expected call at demo/demo_test.go:14 doesn"t match the argument at index 0.// Got: [0xc000060610] ([]*demo.Item)// Want: is equal to [0xc0000605b0] ([]*demo.Item)// demo/controller.go:269: missing call(s) to *demo.MockSaver.Save(is equal to [0xc0000605b0] ([]*demo.Item)) demo/demo_test.go:14// demo/controller.go:269: aborting test due to missing call(s)func TestSaveToFile(t *testing.T) {ctrl := gomock.NewController(t)defer ctrl.Finish()mockSaver := NewMockSaver(ctrl)mockSaver.EXPECT().Save([]*Item{{Name: "bar"}})Save(mockSaver, []*Item{{Name: "foo"}})}// 优化后错误日志如下，此时不仅能看到diff，也能看到差异是什么//--- FAIL: TestSaveToFileV2 (0.00s)// demo/demo.go:12: Unexpected call to *demo.MockSaver.Save([[0xc00009e5f0]]) at demo/demo.go:12 because: // expected call at demo/demo_test.go:23 doesn"t match the argument at index 0.// Got: [{"Name":"foo"}]// Want: [{"Name":"bar"}]// demo/controller.go:269: missing call(s) to *demo.MockSaver.Save([{"Name":"bar"}]) demo/demo_test.go:23// demo/controller.go:269: aborting test due to missing call(s)func TestSaveToFileV2(t *testing.T) {ctrl := gomock.NewController(t)defer ctrl.Finish()mockSaver := NewMockSaver(ctrl)mockSaver.EXPECT().Save(eq([]*Item{{Name: "bar"}})) // 注意这里调用了 eq 方法Save(mockSaver, []*Item{{Name: "foo"}})}func eq(want interface{}) gomock.Matcher {return gomock.GotFormatterAdapter(gomock.GotFormatterFunc(func(got interface{}) string {b, _ := json.Marshal(got)return string(b)},),gomock.WantFormatter(gomock.StringerFunc(func() string {b, _ := json.Marshal(want)return string(b)}),gomock.Eq(want),),)} 关键词：
