mockery

README

mockery

mockery provides the ability to easily generate mocks for golang interfaces using the stretchr/testify/mock package. It removes the boilerplate coding required to use mocks.

Installation

Github Release

Visit the releases page to download one of the pre-built binaries for your platform.

Docker

Use the Docker image

docker pull vektra/mockery

Homebrew

Install through homebrew

brew install vektra/tap/mockery
brew upgrade mockery

go get

Alternatively, you can use the DEPRECATED method of:

go get github.com/vektra/mockery/.../

to get a development version of the software.

The SemVer variable by default is 1.0.0 and is overwritten during build steps to the git tagged version. For backwards-compatibility reasons, SemVer in source will remain at 1.0.0. This will eventually be changed over to 0.0.0-dev. Keep in mind that if using the go get version of downloading, mockery will not correctly specify its version.

Examples

Simplest case

Given this is in string.go

package test

type Stringer interface {
	String() string
}

Run: mockery -name=Stringer and the following will be output to mocks/Stringer.go:

package mocks

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

type Stringer struct {
	mock.Mock
}

func (m *Stringer) String() string {
	ret := m.Called()

	var r0 string
	if rf, ok := ret.Get(0).(func() string); ok {
		r0 = rf()
	} else {
		r0 = ret.Get(0).(string)
	}

	return r0
}

Next level case

See github.com/jaytaylor/mockery-example for the fully runnable version of the outline below.

package main

import (
	"fmt"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/service/s3"
	"github.com/jaytaylor/mockery-example/mocks"
	"github.com/stretchr/testify/mock"
)

func main() {
	mockS3 := &mocks.S3API{}

	mockResultFn := func(input *s3.ListObjectsInput) *s3.ListObjectsOutput {
		output := &s3.ListObjectsOutput{}
		output.SetCommonPrefixes([]*s3.CommonPrefix{
			&s3.CommonPrefix{
				Prefix: aws.String("2017-01-01"),
			},
		})
		return output
	}

	// NB: .Return(...) must return the same signature as the method being mocked.
	//     In this case it's (*s3.ListObjectsOutput, error).
	mockS3.On("ListObjects", mock.MatchedBy(func(input *s3.ListObjectsInput) bool {
		return input.Delimiter != nil && *input.Delimiter == "/" && input.Prefix == nil
	})).Return(mockResultFn, nil)

	listingInput := &s3.ListObjectsInput{
		Bucket:    aws.String("foo"),
		Delimiter: aws.String("/"),
	}
	listingOutput, err := mockS3.ListObjects(listingInput)
	if err != nil {
		panic(err)
	}

	for _, x := range listingOutput.CommonPrefixes {
		fmt.Printf("common prefix: %+v\n", *x)
	}
}

Imports

mockery pulls in all the same imports used in the file that contains the interface so that package types will work correctly. It then runs the output through the imports package to remove any unnecessary imports (as they'd result in compile errors).

Types

mockery should handle all types. If you find it does not, please report the issue.

Return Value Provider Functions

If your tests need access to the arguments to calculate the return values, set the return value to a function that takes the method's arguments as its own arguments and returns the return value. For example, given this interface:

package test

type Proxy interface {
  passthrough(ctx context.Context, s string) string
}

The argument can be passed through as the return value:

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

Mock.On("passthrough", mock.AnythingOfType("context.Context"), mock.AnythingOfType("string")).Return(func(ctx context.Context, s string) string {
    return s
})

Requirements

Return must be passed the same argument count and types as expected by the interface. If the return argument signature of passthrough in the above example was instead (string, error) in the interface, Return would also need a second argument to define the error value.

If any return argument is missing, github.com/stretchr/testify/mock.Arguments.Get will emit a panic.

For example, panic: assert: arguments: Cannot call Get(0) because there are 0 argument(s). [recovered] indicates that Return was not provided any arguments but (at least one) was expected based on the interface. Get(1) would indicate that the Return call is missing a second argument, and so on.

Notes

This approach should be used judiciously, as return values should generally not depend on arguments in mocks; however, this approach can be helpful for situations like passthroughs or other test-only calculations.

Name

The -name option takes either the name or matching regular expression of interface to generate mock(s) for.

All

It's common for a big package to have a lot of interfaces, so mockery provides -all. This option will tell mockery to scan all files under the directory named by -dir ("." by default) and generates mocks for any interfaces it finds. This option implies -recursive=true.

-all was designed to be able to be used automatically in the background if required.

Recursive

Use the -recursive option to search subdirectories for the interface(s). This option is only compatible with -name. The -all option implies -recursive=true.

Output

mockery always generates files with the package mocks to keep things clean and simple. You can control which mocks directory is used by using -output, which defaults to ./mocks.

In Package (-inpkg) and KeepTree (-keeptree)

For some complex repositories, there could be multiple interfaces with the same name but in different packages. In that case, -inpkg allows generate the mocked interfaces directly in the package that it mocks.

In the case you don't want to generate the mocks into the package but want to keep a similar structure, use the option -keeptree.

Specifying File (-filename) and Struct Name (-structname)

Use the -filename and -structname to override the default generated file and struct name. These options are only compatible with non-regular expressions in -name, where only one mock is generated.

Casing

mockery generates files using the casing of the original interface name. This can be modified by specifying -case=underscore to format the generated file name using underscore casing.

Debug

Use mockery -print to have the resulting code printed out instead of written to disk.

Mocking interfaces in main

When your interfaces are in the main package you should supply the -inpkg flag. This will generate mocks in the same package as the target code avoiding import issues.

Semantic Versioning

The versioning in this project applies only to the behavior of the mockery binary itself. This project explicitly does not promise a stable internal API, but rather a stable executable. The versioning applies to the following:

1. CLI arguments.
2. Parsing of Golang code. New features in the Golang language will be supported in a backwards-compatible manner, except during major version bumps.
3. Behavior of mock objects. Mock objects can be considered to be part of the public API.
4. Behavior of mockery given a set of argments.

What the version does not track:

1. The interfaces, objects, methods etc. in the vektra/mockery package.
2. Compatibility of go get-ing mockery with new or old versions of Golang.