pure esm test library

idea-for-pure-esm-test-library.md

Lightweight es module (esm) testing library

I want to build a small test library with a similar api to bdd frameworks like jest but globals, runner or assertion library.

• Bring your own runner.
• Bring your own assertions.

This is possible because of projects like the web test runner which allows for custom frameworks to be used.

I don't need all the options provided by mocha and jest at least not at the moment.

The goals are:

• Tests can be run in any ES module environment. Browser, deno, node (with {"type": "module"}).
• Support snapshots in @web/test-runner. Perhaps a method that can attach a snapshot method to the assertion library being used, that can identify the current test and add it to the snapshot list.
• By default tests run concurrently, but a test / suite can be marked as serial to run sequentially.

Things I want in the future:

• Mark tests / suites as expecting failure. This can be used to make a test fail and show up in the console, but not fail the test suite.

For now the interface should be based on the expected output for @web/test-runner-core

interface TestResultError {
  message: string;
  name?: string;
  stack?: string;
  expected?: string;
  actual?: string;
}

interface TestSuiteResult {
  name: string;
  /**
   * Each suite represents a context.
   */
  suites: TestSuiteResult[];
  tests: TestResult[];
}

interface TestResult {
  name: string;
  passed: boolean;
  skipped: boolean;
  duration?: number;
  error?: TestResultError;
}

/**
 * The results that are reported back to the test runner.
 */
interface TestSession {
  /**
   * Did the test session pass?
   */
  passed?: boolean;
  /**
   * The list of errors if any.
   */
  errors: TestResultError[];
  /**
   * All the test results.
   */
  testResults?: TestSuiteResult;
}