jest-serial-runner/README.md

Extending the Jest default runner to run tests serially by default

# `jest-serial-runner`

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<p align="center">
  Extending the <a href="https://jestjs.io/">Jest</a>
  default runner to run tests serially by default
</p>

---

Simple wrapper over the default Jest runner that forces serial execution of test files. This is equivalent to running with `--runInBand` flag by default.

**Why?** Sometimes you have limited/restricted resources on the test machine (like in a docker container) and running the default `jest-runner` always runs in parallel unless specified otherwise. Integration tests are another scenario where running concurrent instances causes issues so using this runner ensures only 1 test runs at a time.

## Installation

```sh
npm install jest-serial-runner --save-dev
```

## Usage

**Option 1:** Specify the runner in your `Jest` config

```jsonc
/* jest.config.json */
{
    // ...
    "runner": "jest-serial-runner"
    // ...
}
```

**Option 2:** To specify the runner for a subset of files such as for integration tests.

```js
/* jest.config.js */
module.exports = {
    // ...
    projects: [
        {
            // Uses the jest default runner for specification testing
            displayName: "UNIT",
            testMatch: ["<rootDir>/src/**/__tests__/*.spec.ts"]
        },
        {
            // Uses the serial runner instead for integration test files
            displayName: "INTEGRATION",
            runner: "jest-serial-runner",
            testMatch: ["<rootDir>/tests/**/*.integration-test.ts"]
        }
    ]
}
```

## Contributors

**Thank you to all of our [contributors](./package.json)!**

PR's & Issue contributions welcome! Please adhere to
[contributing guidelines](./CONTRIBUTING.md)
or your submission will be closed or delayed.