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Developing

Intern is written in TypeScript. The various build lifecycle steps (build, test, etc.) are handled through npm, and are implemented by scripts in the @theintern/dev package.

Code style

The source is formatted using prettier 1.9+ during a pre-commit hook, so style should be mostly taken care of.

💡Prettier doesn't (yet) reflow comments; those should be wrapped at 80 characters. Long lines for URLs are fine.

Building Intern

⚠️ Note that running the self tests requires Intern requires Node 10.16+.

Before you can do much else, you'll need to install Intern’s development dependencies:

$ npm install

To build Intern, just run:

$ npm run build

Running Self-Tests

To run the existing unit tests in Node, use:

$ npm test

To run unit tests in Node and a local instance of Chrome, use:

$ npm test config=@wd

Intern’s self tests work by using two different builds of the current version of Intern, one in _tests and one in _build. Both instances are generated when building Intern. The version in _tests is then used to run tests against the version in _build.

Writing Self-Tests

Tests are in the tests directory, and the test config is the intern.json file in the project root. Tests are organized by type in unit, functional, and benchmark directories. The directory structure within each type should mirror the main src directory structure. For example, unit tests for src/lib/executors/Executor should go in tests/unit/lib/executors/Executor.

There are a couple of techniques that can make writing unit tests faster.

  • Intern includes a watch script that will rebuild source and test files when they're updated.
  • Disable coverage with a coverage= command line option.
  • Only run the suite that’s being edited.

Say you’re working on tests in tests/unit/lib/Environment.ts. Start the watcher with npm run watch. Whenever you write a new test in Environment.ts, run the updated suite with

npm test suites=_tests/tests/unit/lib/Environment.js coverage=

TypeScript

As with the main Intern source, self-tests are written in TypeScript. The tests have their own tsconfig.json file that inherits from the main Intern tsconfig. The key difference is that the test tsconfig file defines a path mapping for the non-relative “src” path. This saves a bit of typing during test writing, but the main advantage is that this path can be re-mapped at runtime to point to files in the _build/src directory.

Dojo 2 loader

Self tests in the browser use the Dojo loader so that individual modules can be loaded in the browser, and to allow module dependencies to be mocked. The self-tests use the built-in dojo2 loader script.