type-tester

A tester to check expected type errors.

🏁 Goal

This package provides utility to verify that the type you have written stricter reports expected type errors, for TypeScript.

💿 Installation

Use npm or a compatible tool to install this package.

npm install type-tester typescript

• Requires Node.js >=6.0.0.

📖 Usage

1. Write fixture files.
2. Write test files.
3. Run test files with test runner such as mocha.

1. Write fixture files.

The fixture file should include the situation of type error. You must add directive comments such as // @expected 2345 for each line of expected errors. The number is the error code of TypeScript.

For example: test/fixtures/event-target-shim/fixture.ts

2. Write test files.

The test file should execute TypeTester#verify() method with the path to the fixture files and compiler options.

For example: test/example.ts

3. Run test files with test runner such as mocha.

Because the TypeTester#verify() method defines test cases with describe / it global functions, you must run it with test runners.

For example:

mocha test/example.ts --require ts-node/register

  this test runs the type tester merely.
    fixture.ts
      √ should have an error TS2345 at L98.
      √ should have an error TS2345 at L101.
      √ should have an error TS7006 at L102.
      √ should have an error TS2345 at L105.
      √ should have an error TS7006 at L106.
      √ should have an error TS2322 at L108.
      √ should have an error TS2322 at L109.
      √ should have an error TS2345 at L152.

  8 passing (11ms)

📚 API References

TypeTester class

The class to verify expected type errors.

constructor(ts: typeof import("typescript"), options: TypeTester.Options)

Parameters

Name	Description
ts	API to use type checking.
options.describe	Optional. Function to declare test suites. Use global.describe by default.
options.it	Optional. Function to declare test cases. Use global.it by default.

tester.verify(fixtureFiles: ReadonlyArray<string>, compilerOptions: ts.CompilerOptions): void

Verify the given fixture files.

Parameters

Name	Description
fixtureFiles	Path to fixture files.
compilerOptions	Compiler options to verify the fixture files.

📰 Release notes

• https://github.com/mysticatea/type-tester/releases

❤️ Contributing

Contribution is welcome!

Please use GitHub issues and pull requests.

Development tools

• npm run build generates files into dist directory.
• npm run clean removes temporary files.
• npm run coverage opens the coverage report the last npm test command generated.
• npm run lint runs ESLint.
• npm test runs tests.
• npm run watch runs tests on each file edits.