If you find any bugs or have feature requests, please feel free to create an issue.

gomockhandler is handler of golang/mock, as the name implies.

gomockhandler use one config file to generate all mocks.

With gomockhandler,

  • You can generate mocks in parallel
  • You can check if mock is up-to-date

  • You can manage your mocks in one config file

Here is some example of the mock being generated in half the time with gomockhandler. (I ran mockgen to generate same mocks in go generate ./...)

Screen Shot 2021-03-25 at 11 55 54

Screen Shot 2021-03-25 at 11 56 29


Some of you may often manage your mocks with go generate like below.

//go:generate mockgen -source=$GOFILE -destination=mock_$GOFILE -package=$GOPACKAG

But, it will take long time to generate a log of mocks with go generate ./..., because go generate executes mockgen one by one.

And we cannot easily check if mock is up-to-date.

gomockhandler is created to solve all of these problems.

And with this background, it is designed to make it easy to switch from managing mocks with go generate to managing mocks with gomockhandler.


You have to install mockgen first.

Go version < 1.16

GO111MODULE=on go get github.com/golang/mock/mockgen
GO111MODULE=on go get github.com/sanposhiho/gomockhandler

Go 1.16+

go install github.com/golang/mock/mockgen
go install github.com/sanposhiho/gomockhandler

How to use

gomockhandler is designed to be simple and does only three things.

  • generate/edit a config with CLI
  • generate mocks from config
  • check if mocks are up-to-date
-config string
  The path to config file.
  The default value is "./gomockhandler.json"


You need a config for gomockhandler.

However, you don’t need to generate/edit the config directly, it can be generated/edited from CLI.

configuring a new mock

You can configure a new mock to be generated with CLI. It will also check if mockgen will run correctly with that option.

If a config file does not exist, a config file will be created.

(It is RECOMMENDED to name the config file gomockhandler.json, and place it in a location where the gomockhandler is likely to be run frequently.)

mockgen has two modes of operation: source and reflect, and gomockhandler support both.

See golang/mock#running-mockgen for more information about the two modes and mockgen options.

Source mode:

gomockhandler -config=/path/to/gomockhandler.json -source=foo.go -destination=./mock/ [other mockgen options]

Reflect mode:

gomockhandler -config=/path/to/gomockhandler.json -destination=./mock/ [other mockgen options] database/sql/driver Conn,Driver

You can use all options of mockgen to add a new mock.

For example, suppose you want to configure the mock generated by the following mockgen command to be generated by gomockhandler

mockgen -source=foo.go -destination=../mock/

The following command will add the information of the mock you want to generate to the configuration. As you can see, you just need to think about the option config. (The default value is ./gomockhandler.json)

gomockhandler -config=/path/to/gomockhandler.json -source=foo.go -destination=../mock/

gomockhandler is designed to make it easy to switch from managing mocks with go generate to managing mocks with gomockhandler.

If you use go:generate to execute mockgen now, you can generate the config file by rewriting go:generate comment a little bit.

Replace from mockgen to gomockhandler -config=/path/to/gomockhandler.json in all go:generate comments, and run go generate ./... in your project. And then,

- //go:generate mockgen -source=$GOFILE -destination=mock_$GOFILE -package=$GOPACKAG
+ //go:generate gomockhandler -config=/path/to/gomockhandler.json -source=$GOFILE -destination=mock_$GOFILE -package=$GOPACKAG

After generating the config, your go:generate comments are no longer needed. You’ve been released from a slow-mockgen with go generate!

Let’s delete all go:generate comments for mockgen in your project.

delete mocks to be generated from config

You can remove the mocks to be generated from the config.

gomockhandler -config=/path/to/gomockhandler.json -destination=./mock/user.go deletemock 

generate mock

You can generate all mocks from config.

gomockhandler -config=/path/to/gomockhandler.json mockgen

check if mock is up-to-date

You can check if the mock is generated based on the latest interface.

It is useful for ci.

gomockhandler -config=/path/to/gomockhandler.json check

If some mocks are not up to date, you can see the error and gomockhandler will exit with exit-code 1

2021/03/10 22:17:12 [WARN] mock is not up to date. source: ./interfaces/user.go, destination: ./interfaces/../mock/user.go
2021/03/10 22:17:12 mocks is not up-to-date

edit config manually

You can edit the config manually.

But, it is RECOMMENDED to use CLI, especially for adding/editing mocks. (This is because CLI will check if mockgen works correctly with that option, and then edit the config.)

The config json file has the following format.

	"mocks": {
		"mock/user.go": {
			"checksum": "7E+SZ7+e0tK5wBe15dJLvA==",
			"mode": "SOURCE_MODE",
			"source_mode_runner": {
				"source": "interfaces/user.go",
				"destination": "mock/user.go"
		"mock/user2.go": {
			"checksum": "BEqA5NiFCJa3De8kKXYf3g==",
			"mode": "REFLECT_MODE",
			"reflect_mode_runner": {
				"package_name": "playground/interfaces",
				"interfaces": "User2",
				"destination": "mock/user2.go"

As mentioned above, there are two modes of mockgen, and the format of the config is slightly different depending on which mode you are using. In the ***mode-runner field, specify the option to be used when running mockgen.

In the checksum field, the checksum of the currently generated mock is stored. With this checksum, the gomockhandler checks if the mock is the same as the mock generated from the latest interface.