121 lines
3.6 KiB
Markdown
121 lines
3.6 KiB
Markdown
 [](https://github.com/matryer/moq/actions?query=branch%3Amaster) [](https://goreportcard.com/report/github.com/matryer/moq)
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Interface mocking tool for go generate.
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By [Mat Ryer](https://twitter.com/matryer) and [David Hernandez](https://github.com/dahernan), with ideas lovingly stolen from [Ernesto Jimenez](https://github.com/ernesto-jimenez).
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### What is Moq?
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Moq is a tool that generates a struct from any interface. The struct can be used in test code as a mock of the interface.
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above: Moq generates the code on the right.
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You can read more in the [Meet Moq blog post](http://bit.ly/meetmoq).
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### Installing
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To start using Moq, just run go get:
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```
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$ go get github.com/matryer/moq
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```
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### Usage
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```
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moq [flags] source-dir interface [interface2 [interface3 [...]]]
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-fmt string
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go pretty-printer: gofmt, goimports or noop (default gofmt)
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-out string
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output file (default stdout)
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-pkg string
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package name (default will infer)
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-stub
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return zero values when no mock implementation is provided, do not panic
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Specifying an alias for the mock is also supported with the format 'interface:alias'
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Ex: moq -pkg different . MyInterface:MyMock
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```
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**NOTE:** `source-dir` is the directory where the source code (definition) of the target interface is located.
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It needs to be a path to a directory and not the import statement for a Go package.
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In a command line:
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```
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$ moq -out mocks_test.go . MyInterface
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```
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In code (for go generate):
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```go
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package my
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//go:generate moq -out myinterface_moq_test.go . MyInterface
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type MyInterface interface {
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Method1() error
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Method2(i int)
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}
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```
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Then run `go generate` for your package.
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### How to use it
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Mocking interfaces is a nice way to write unit tests where you can easily control the behaviour of the mocked object.
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Moq creates a struct that has a function field for each method, which you can declare in your test code.
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In this example, Moq generated the `EmailSenderMock` type:
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```go
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func TestCompleteSignup(t *testing.T) {
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var sentTo string
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mockedEmailSender = &EmailSenderMock{
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SendFunc: func(to, subject, body string) error {
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sentTo = to
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return nil
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},
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}
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CompleteSignUp("me@email.com", mockedEmailSender)
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callsToSend := len(mockedEmailSender.SendCalls())
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if callsToSend != 1 {
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t.Errorf("Send was called %d times", callsToSend)
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}
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if sentTo != "me@email.com" {
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t.Errorf("unexpected recipient: %s", sentTo)
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}
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}
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func CompleteSignUp(to string, sender EmailSender) {
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// TODO: this
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}
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```
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The mocked structure implements the interface, where each method calls the associated function field.
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## Tips
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* Keep mocked logic inside the test that is using it
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* Only mock the fields you need
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* It will panic if a nil function gets called
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* Name arguments in the interface for a better experience
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* Use closured variables inside your test function to capture details about the calls to the methods
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* Use `.MethodCalls()` to track the calls
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* Use `go:generate` to invoke the `moq` command
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* If Moq fails with a `go/format` error, it indicates the generated code was not valid.
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You can run the same command with `-fmt noop` to print the generated source code without attempting to format it.
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This can aid in debugging the root cause.
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## License
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The Moq project (and all code) is licensed under the [MIT License](LICENSE).
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The Moq logo was created by [Chris Ryer](http://chrisryer.co.uk) and is licensed under the [Creative Commons Attribution 3.0 License](https://creativecommons.org/licenses/by/3.0/).
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