electron/docs/development/testing.md

Testing

We aim to keep the code coverage of Electron high. We ask that all pull request not only pass all existing tests, but ideally also add new tests to cover changed code and new scenarios. Ensuring that we capture as many code paths and use cases of Electron as possible ensures that we all ship apps with fewer bugs.

This repository comes with linting rules for both JavaScript and C++ – as well as unit and integration tests. To learn more about Electron's coding style, please see the coding-style document.

Linting

To ensure that your JavaScript is in compliance with the Electron coding style, run npm run lint-js, which will run standard against both Electron itself as well as the unit tests. If you are using an editor with a plugin/addon system, you might want to use one of the many StandardJS addons to be informed of coding style violations before you ever commit them.

To run standard with parameters, run npm run lint-js -- followed by arguments you want passed to standard.

To ensure that your C++ is in compliance with the Electron coding style, run npm run lint-cpp, which runs a cpplint script. We recommend that you use clang-format and prepared a short tutorial.

There is not a lot of Python in this repository, but it too is governed by coding style rules. npm run lint-py will check all Python, using pylint to do so.

Unit Tests

To run all unit tests, run npm run test. The unit tests are an Electron app (surprise!) that can be found in the spec folder. Note that it has its own package.json and that its dependencies are therefore not defined in the top-level package.json.

To run only specific tests matching a pattern, run npm run test -- -g=PATTERN, replacing the PATTERN with a regex that matches the tests you would like to run. As an example: If you want to run only IPC tests, you would run npm run test -- -g ipc.

Testing on Windows 10 devices

Extra steps to run the unit test:

1. Visual Studio 2019 must be installed.
2. Node headers have to be compiled for your configuration.

   ninja -C out\Testing third_party\electron_node:headers
   

3. The electron.lib has to be copied as node.lib.

   cd out\Testing
   mkdir gen\node_headers\Release
   copy electron.lib gen\node_headers\Release\node.lib
   

Missing fonts

Some Windows 10 devices do not ship with the Meiryo font installed, which may cause a font fallback test to fail. To install Meiryo:

1. Push the Windows key and search for Manage optional features.
2. Click Add a feature.
3. Select Japanese Supplemental Fonts and click Install.

Pixel measurements

Some tests which rely on precise pixel measurements may not work correctly on devices with Hi-DPI screen settings due to floating point precision errors. To run these tests correctly, make sure the device is set to 100% scaling.

To configure display scaling:

1. Push the Windows key and search for Display settings.
2. Under Scale and layout, make sure that the device is set to 100%.