Running Golang tests with Jest

First, what are Jest runners?

In a nutshell, Jest is composed of multiple packages that are each one responsible for a specific step in your test run lifecycle. Runners are the packages that focus on “running” tests. Jest provides an interface to plug your own runner on both the interface package, which is in charge of finding files, providing the UX and filtering, and the result reporting package, which basically manages the output of your tests.

The ability to add custom runners is interesting in case you want to run other types of tests than the default ones supported by Jest. In the case of jest-runner-go, the runner will simply run go test against all Go tests files found by the Jest interface and parse the output in a way the Jest result reporting package can understand it and present the results in a more human readable way.

Using jest-runner-go with Jest

Using Jest to test both the Golang backend and the React frontend of an app has brought me a certain peace of mind, especially when running the tests during CI: the output is consistent and clear across my stack when running my tests. Additionally I get features that are not available with go tests like a native watch mode or running tests with a specific pattern which makes the experience of running tests in Go better.

To integrate jest-runner-go in your project, first run yarn add jest jest-runner-go then simply add the following to whichever Jest config you’re using, either jest.config.js or a specific config that will be passed with the --config flag when running Jest, or even the package.json of the project:

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"moduleFileExtensions": \[
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 "go"
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\],
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"runner": "jest-runner-go",
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"testMatch": \[
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 "\*\*/?(\*\_)test.go"
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\]

Then running jest or jest --config my-go-test-config will find all the files matching _test.go, execute go test against each of these files and finally parse the output produced by go test so Jest will get the required data to output.

As mentioned before, most of my use cases for jest-runner-go along with the classic jest-runner include whenever one of my projects uses both Go and React. It’s possible to run the tests of both sides of the project in a single test run by using the --projects flag and pass multiple Jest configs. In the example below, I added the previous config to a config file called gojest.config.js and then used the following command in a small project generated with create-react-app that also includes some Go code with unit tests:

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jest --projects jest.config.js gojest.config.js

which gives us the following output:

Jest-runner-go Recorded by maxime_asciinema.org

Other runners

Other Jest runners have been written these last few months, the most notable ones that I’ve found or been introduced to so far are:

• jest-runner-eslint
• jest-runner-mocha
• jest-runner-prettier
• pyjest

What’s coming next?

This article focused a lot on using jest-runner-go to run Go tests along with Javascript tests, but what if we want to use it to only test Go code?

This case is a tricky one as many Go projects owners don’t want to have a dependency on Node to run their tests, as well as everything that comes with it: a node_modules folder, a package.json and a Jest config.

That’s why I started working on Gojest: a standalone binary to run Go tests using the Jest platform and jest-runner-go. The project is compiled for Linux, macOS and Windows using pkg and is available here. This is purely experimental and is obviously not intended to be used in production given how new and not widely used the project and jest-runner-go currently are.

If you want to get the latest version of Gojest you can either download the binaries from the release page of the project or install them using Docker by running the following:

For macOS

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docker pull maximeheckel/gojest:latest &&
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id=$(docker create maximeheckel/gojest:latest) &&
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docker cp $id:/gojest-macos /usr/local/bin/gojest && (docker rm \$id >/dev/null)

For Linux

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docker pull maximeheckel/gojest:latest &&
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id=$(docker create maximeheckel/gojest:latest) &&
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docker cp $id:/gojest-linux /usr/local/bin/gojest && (docker rm \$id >/dev/null)

For Windows

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docker pull maximeheckel/gojest:latest &&
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id=$(docker create maximeheckel/gojest:latest) &&
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docker cp $id:/gojest-win.exe gojest.exe && (docker rm \$id >/dev/null)

Here’s an example of using Gojest to run unit tests in a Go project:

Gojest running Docker tests Recorded by MaximeHeckel_asciinema.org

I really hope to make jest-runner-go and Gojest stable enough to be used by the Go community in a decent timeframe. If you want to contribute or give feedback, both projects are available on Github at

• https://github.com/MaximeHeckel/jest-runner-go
• https://github.com/MaximeHeckel/gojest

Pull requests are more than welcome.