index.md

mockery

Mockery is a project that creates mock implementations of Golang interfaces. The mocks generated in this project are based off of the github.com/stretchr/testify suite of testing packages.

Why mockery?

When you have an interface like this:

type DB interface {
	Get(val string) string
}

and a function that takes this interface:

func getFromDB(db DB) string {
	return db.Get("ice cream")
}

You can test getFromDB by either instantiating a testing database, or you can simply create a mock implementation of DB using mockery. Mockery can autogenerate a mock implementation that allows us to define assertions on how the mock was used, what to return, and other useful tidbits. We can add a //go:generate directive above our interface:

//go:generate mockery --name DB
type DB interface {
	Get(val string) string
}

inpackage: True # (1)!
with-expecter: True # (2)!
testonly: True # (3)!

1. Generate our mocks next to the original interface
2. Create expecter methods
3. Append _test.go to the filename so the mock object is not packaged

$ go generate  
05 Mar 23 21:49 CST INF Starting mockery dry-run=false version=v2.20.0
05 Mar 23 21:49 CST INF Using config: .mockery.yaml dry-run=false version=v2.20.0
05 Mar 23 21:49 CST INF Walking dry-run=false version=v2.20.0
05 Mar 23 21:49 CST INF Generating mock dry-run=false interface=DB qualified-name=github.com/vektra/mockery/v2/pkg/fixtures/example_project version=v2.20.0

We can then use the mock object in a test:

import (
	"testing"

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

func Test_getFromDB(t *testing.T) {
	mockDB := NewMockDB(t)
	mockDB.EXPECT().Get("ice cream").Return("chocolate").Once()
	flavor := getFromDB(mockDB)
	assert.Equal(t, "chocolate", flavor)
}

Why use mockery over gomock?

1. mockery provides a much more user-friendly API and is less confusing to use
2. mockery utilizes testify which is a robust and highly feature-rich testing framework
3. mockery has rich configuration options that allow fine-grained control over how your mocks are generated
4. mockery's CLI is more robust, user-friendly, and provides many more options
5. mockery supports generics (this may no longer be an advantage if/when gomock supports generics)

Who uses mockery?

- [{ class="center" width="100" }](https://github.com/grafana/grafana) [grafana](https://github.com/grafana/grafana) - [{ class="center" width="100" }](https://github.com/google/skia) [Google Skia](https://github.com/google/skia) - [{ class="center" width="100" }](https://github.com/google/syzkaller) [Google Skyzkaller](https://github.com/google/syzkaller) - [{ class="center" width="100" }](https://github.com/search?q=org%3Ahashicorp%20mockery&type=code) [Hashicorp](https://github.com/search?q=org%3Ahashicorp%20mockery&type=code) - [{ class="center" width="100" }](https://github.com/uber/cadence) [Uber Cadence](https://github.com/uber/cadence) - [{ class="center" width="300" }](https://github.com/jaegertracing/jaeger) [Jaegertracing](https://github.com/jaegertracing/jaeger) - [{ class="center" width="300" }](https://github.com/splunk/kafka-mq-go) [Splunk kafka-mq-go](https://github.com/splunk/kafka-mq-go) - [{ class="center" width="300" }](https://github.com/ignite/cli) - [{ class="center" width="300" }](https://github.com/tendermint/tendermint) - [{ class="center" width="300" }](https://github.com/DataDog/datadog-agent) - [](https://seatgeek.com) - [{ class="center" width="300" }](https://github.com/eksctl-io/eksctl) [eksctl](https://github.com/eksctl-io/eksctl) - [{ class="center" width="300" }](https://github.com/search?q=org%3Amongodb%20mockery&type=code)

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