base on GoMock is a mocking framework for the Go programming language. # gomock [![Build Status][ci-badge]][ci-runs] [![Go Reference][reference-badge]][reference] gomock is a mocking framework for the [Go programming language][golang]. It integrates well with Go's built-in `testing` package, but can be used in other contexts too. This project originates from Google's `golang/mock` repo. Unfortunately, Google no longer maintains this project, and given the heavy usage of gomock project within Uber, we've decided to fork and maintain this going forward at Uber. [Contributions](./CONTRIBUTING.md) are welcome in the form of GitHub issue or PR! ## Supported Go Versions go.uber.org/mock supports all Go versions supported by the official [Go Release Policy](https://go.dev/doc/devel/release#policy). That is, the two most recent releases of Go. ## Installation Install the `mockgen` tool. ``` go install go.uber.org/mock/mockgen@latest ``` To ensure it was installed correctly, use: ``` mockgen -version ``` If that fails, make sure your GOPATH/bin is in your PATH. You can add it with: ``` export PATH=$PATH:$(go env GOPATH)/bin ``` ## Running mockgen `mockgen` has two modes of operation: source and package. ### Source mode Source mode generates mock interfaces from a source file. It is enabled by using the -source flag. Other flags that may be useful in this mode are -imports and -aux_files. Example: ```bash mockgen -source=foo.go [other options] ``` ### Package mode Package mode works by specifying the package and interface names. It is enabled by passing two non-flag arguments: an import path, and a comma-separated list of symbols. You can use "." to refer to the current path's package. Example: ```bash mockgen database/sql/driver Conn,Driver # Convenient for `go:generate`. mockgen . Conn,Driver ``` ### Flags The `mockgen` command is used to generate source code for a mock class given a Go source file containing interfaces to be mocked. It supports the following flags: - `-source`: A file containing interfaces to be mocked. - `-destination`: A file to which to write the resulting source code. If you don't set this, the code is printed to standard output. - `-package`: The package to use for the resulting mock class source code. If you don't set this, the package name is `mock_` concatenated with the package of the input file. - `-imports`: A list of explicit imports that should be used in the resulting source code, specified as a comma-separated list of elements of the form `foo=bar/baz`, where `bar/baz` is the package being imported and `foo` is the identifier to use for the package in the generated source code. - `-aux_files`: A list of additional files that should be consulted to resolve e.g. embedded interfaces defined in a different file. This is specified as a comma-separated list of elements of the form `foo=bar/baz.go`, where `bar/baz.go` is the source file and `foo` is the package name of that file used by the -source file. - `-build_flags`: (package mode only) Flags passed verbatim to `go list`. - `-mock_names`: A list of custom names for generated mocks. This is specified as a comma-separated list of elements of the form `Repository=MockSensorRepository,Endpoint=MockSensorEndpoint`, where `Repository` is the interface name and `MockSensorRepository` is the desired mock name (mock factory method and mock recorder will be named after the mock). If one of the interfaces has no custom name specified, then default naming convention will be used. - `-self_package`: The full package import path for the generated code. The purpose of this flag is to prevent import cycles in the generated code by trying to include its own package. This can happen if the mock's package is set to one of its inputs (usually the main one) and the output is stdio so mockgen cannot detect the final output package. Setting this flag will then tell mockgen which import to exclude. - `-copyright_file`: Copyright file used to add copyright header to the resulting source code. - `-debug_parser`: Print out parser results only. - `-write_package_comment`: Writes package documentation comment (godoc) if true. (default true) - `-write_generate_directive`: Add //go:generate directive to regenerate the mock. (default false) - `-write_source_comment`: Writes original file (source mode) or interface names (package mode) comment if true. (default true) - `-typed`: Generate Type-safe 'Return', 'Do', 'DoAndReturn' function. (default false) - `-exclude_interfaces`: Comma-separated names of interfaces to be excluded For an example of the use of `mockgen`, see the `sample/` directory. In simple cases, you will need only the `-source` flag. ## Building Mocks ```go type Foo interface { Bar(x int) int } func SUT(f Foo) { // ... } ``` ```go func TestFoo(t *testing.T) { ctrl := gomock.NewController(t) m := NewMockFoo(ctrl) // Asserts that the first and only call to Bar() is passed 99. // Anything else will fail. m. EXPECT(). Bar(gomock.Eq(99)). Return(101) SUT(m) } ``` ## Building Stubs ```go type Foo interface { Bar(x int) int } func SUT(f Foo) { // ... } ``` ```go func TestFoo(t *testing.T) { ctrl := gomock.NewController(t) m := NewMockFoo(ctrl) // Does not make any assertions. Executes the anonymous functions and returns // its result when Bar is invoked with 99. m. EXPECT(). Bar(gomock.Eq(99)). DoAndReturn(func(_ int) int { time.Sleep(1*time.Second) return 101 }). AnyTimes() // Does not make any assertions. Returns 103 when Bar is invoked with 101. m. EXPECT(). Bar(gomock.Eq(101)). Return(103). AnyTimes() SUT(m) } ``` ## Modifying Failure Messages When a matcher reports a failure, it prints the received (`Got`) vs the expected (`Want`) value. ```shell Got: [3] Want: is equal to 2 Expected call at user_test.go:33 doesn't match the argument at index 1. Got: [0 1 1 2 3] Want: is equal to 1 ``` ### Modifying `Want` The `Want` value comes from the matcher's `String()` method. If the matcher's default output doesn't meet your needs, then it can be modified as follows: ```go gomock.WantFormatter( gomock.StringerFunc(func() string { return "is equal to fifteen" }), gomock.Eq(15), ) ``` This modifies the `gomock.Eq(15)` matcher's output for `Want:` from `is equal to 15` to `is equal to fifteen`. ### Modifying `Got` The `Got` value comes from the object's `String()` method if it is available. In some cases the output of an object is difficult to read (e.g., `[]byte`) and it would be helpful for the test to print it differently. The following modifies how the `Got` value is formatted: ```go gomock.GotFormatterAdapter( gomock.GotFormatterFunc(func(i any) string { // Leading 0s return fmt.Sprintf("%02d", i) }), gomock.Eq(15), ) ``` If the received value is `3`, then it will be printed as `03`. [golang]: http://go.dev/ [ci-badge]: https://github.com/uber-go/mock/actions/workflows/test.yaml/badge.svg [ci-runs]: https://github.com/uber-go/mock/actions [reference-badge]: https://pkg.go.dev/badge/go.uber.org/mock.svg [reference]: https://pkg.go.dev/go.uber.org/mock ", Assign "at most 3 tags" to the expected json: {"id":"4931","tags":[]} "only from the tags list I provide: [{"id":77,"name":"3d"},{"id":89,"name":"agent"},{"id":17,"name":"ai"},{"id":54,"name":"algorithm"},{"id":24,"name":"api"},{"id":44,"name":"authentication"},{"id":3,"name":"aws"},{"id":27,"name":"backend"},{"id":60,"name":"benchmark"},{"id":72,"name":"best-practices"},{"id":39,"name":"bitcoin"},{"id":37,"name":"blockchain"},{"id":1,"name":"blog"},{"id":45,"name":"bundler"},{"id":58,"name":"cache"},{"id":21,"name":"chat"},{"id":49,"name":"cicd"},{"id":4,"name":"cli"},{"id":64,"name":"cloud-native"},{"id":48,"name":"cms"},{"id":61,"name":"compiler"},{"id":68,"name":"containerization"},{"id":92,"name":"crm"},{"id":34,"name":"data"},{"id":47,"name":"database"},{"id":8,"name":"declarative-gui "},{"id":9,"name":"deploy-tool"},{"id":53,"name":"desktop-app"},{"id":6,"name":"dev-exp-lib"},{"id":59,"name":"dev-tool"},{"id":13,"name":"ecommerce"},{"id":26,"name":"editor"},{"id":66,"name":"emulator"},{"id":62,"name":"filesystem"},{"id":80,"name":"finance"},{"id":15,"name":"firmware"},{"id":73,"name":"for-fun"},{"id":2,"name":"framework"},{"id":11,"name":"frontend"},{"id":22,"name":"game"},{"id":81,"name":"game-engine "},{"id":23,"name":"graphql"},{"id":84,"name":"gui"},{"id":91,"name":"http"},{"id":5,"name":"http-client"},{"id":51,"name":"iac"},{"id":30,"name":"ide"},{"id":78,"name":"iot"},{"id":40,"name":"json"},{"id":83,"name":"julian"},{"id":38,"name":"k8s"},{"id":31,"name":"language"},{"id":10,"name":"learning-resource"},{"id":33,"name":"lib"},{"id":41,"name":"linter"},{"id":28,"name":"lms"},{"id":16,"name":"logging"},{"id":76,"name":"low-code"},{"id":90,"name":"message-queue"},{"id":42,"name":"mobile-app"},{"id":18,"name":"monitoring"},{"id":36,"name":"networking"},{"id":7,"name":"node-version"},{"id":55,"name":"nosql"},{"id":57,"name":"observability"},{"id":46,"name":"orm"},{"id":52,"name":"os"},{"id":14,"name":"parser"},{"id":74,"name":"react"},{"id":82,"name":"real-time"},{"id":56,"name":"robot"},{"id":65,"name":"runtime"},{"id":32,"name":"sdk"},{"id":71,"name":"search"},{"id":63,"name":"secrets"},{"id":25,"name":"security"},{"id":85,"name":"server"},{"id":86,"name":"serverless"},{"id":70,"name":"storage"},{"id":75,"name":"system-design"},{"id":79,"name":"terminal"},{"id":29,"name":"testing"},{"id":12,"name":"ui"},{"id":50,"name":"ux"},{"id":88,"name":"video"},{"id":20,"name":"web-app"},{"id":35,"name":"web-server"},{"id":43,"name":"webassembly"},{"id":69,"name":"workflow"},{"id":87,"name":"yaml"}]" returns me the "expected json"