esm-test-parser

Esm test parser

This library is not a test runner. It's a utility for creating test runner plugins.

esm-test-parser is a library for converting ESM modules, classes, and objects into a structured collection of tests. It analyzes a given JavaScript module/object and returns an array of tests which can then be added to test runners that support dynamic test creation.

Features

• Parameterized Tests: Define multiple test cases.

• Execution Filtering: Built-in support for only to isolate specific tests.

• Nested Test Context Support: Tracks the full hierarchy of test groups, allowing you to provide a specific context (this) for each level of nesting via testContextLookup.

• Flexible Identification: Detects tests from functions, objects, and class instances.

• Built-in Hooks: Ability to specify nested custom hooks like beforeEach, afterEach, beforeAll, and afterAll.

• Nested Test Objects Specific

  • Hierarchical Grouping: Organise tests into logical suites using nested object structures.
  • Sequential Filtering: Use only: true, only: number, or only: '*' to control execution flow within objects.
  • Implicit Titles: Object keys automatically serve as test and group titles.
  • Parameterized Tests: Use arrays of arguments to define multiple cases for a single test key.
  • Metadata via Properties: Use [test.title], [test.cases], and [only] directly on object and function members to override titles or define filtering and cases.

• Pure Test Functions Specific

  • Metadata via Properties: Attach [test.title], [test.cases], and [only] directly to function objects.
  • Automatic Discovery: All exported functions (except reserved hooks) are treated as tests.
  • Reserved Hooks: Export functions named beforeEach, afterEach, beforeAll, or afterAll for setup/teardown.

• Test Classes Specific

  • Declarative Testing: Use classes as suites and methods as tests.
  • Rich Metadata Decorators: Use @testCase, @testOnly, and @testTitle for clean, expressive definitions.
  • Instance Context: Tests run within the class instance context, allowing for shared state via this.
  • Flexible Filtering: Apply @testOnly to individual methods or the entire class.

Installation

npm install esm-test-parser --save-dev

Advanced Examples

Nested Object Tests

The most flexible way to define tests is using nested objects. This allows for clear grouping and hierarchy.

// Parse a module
import * as MyTests from './test-module.js' // see some examples of the test-module.js below
const tests = extractTestsFromModule(MyTests);

// test-module.js
import { extractTestsFromModule } from 'esm-test-parser';

// 1. Define your tests using objects
export const MyMathTests = {
  'Basic Operations': {
    'Addition': {
      '1 + 1 = 2': () => { /* assert logic */ },
      '2 + 2 = 4': () => { /* assert logic */ }
    },
    'Multiplication': {
      '3 * 3 = 9': () => { /* assert logic */ }
  },
  
  // Optional: Run test(s) in isolation.
  // true: run the first preceding test, number: run [number]] preceding tests, '*': run all preceding tests.
  only: true, // can also be a number (e.g., 2) or '*'

  // Parameterized tests in objects
  'Calculate Square Root ($i)': [
    [9, 3],
    [16, 4],
    function(input, expected) {
      // assert(Math.sqrt(input) === expected)
    }
  ],

  // Optional: Built-in hooks
  beforeEach: () => { /* setup */ },
  afterEach: () => { /* teardown */ }
};

Classes with Decorators

// test-module.js
import { testCase, testTitle, testOnly } from 'esm-test-parser';

@testTitle('Math Suite')
export class MathTests {

  // Optional: Test cases
  @testCase(1, 1, 2)
  @testCase(2, 3, 5)
  ['add $1 + $2 = $3'](a, b, expected) {
    // test logic
  }

  // Optional: Run test methods in isolation.
  @testOnly(true | number | '*')
  onlyThisTest() {
    // only this test will run
  }
}

Functional Tests

Pure functions can be used as tests. You can attach metadata using the test and only keywords.

// test-module.js
import { only, test } from 'esm-test-parser';

// A simple test function
export function basicTest() { /* ... */ }

// Optional: Run test functions in isolation. 
// true: run preceding test, number: run N preceding tests, '*': run all preceding tests.
customTest[only] = true; // can also be a number or '*'

// Optional: Set a custom title
customTest[test.title] = "This is a custom title";
export function customTest() { /* ... */ }

// Optional: Parameterized functional tests
parameterizedTest[test.title] = "Testing $1";
parameterizedTest[test.cases] = [
  ['case A'],
  ['case B']
];
export function parameterizedTest(value) {
  // Runs twice with 'case A' and 'case B'
}

// Hooks are exported as functions
export function beforeAll() { /* ... */ }

API

extractTestsFromModule(moduleToParse, options)

Extracts tests from a given module based on the provided options.

• moduleToParse: The JavaScript module or object containing test definitions.
• options: A TestParserOptions object.
  • builtInFunctions: Array of function names to treat as hooks.
  • testContextLookup: Function to resolve this context for tests.
  • sort: Sorting method ('all', 'groupsOnly', 'testsOnly', 'none').
  • parserFlags: Flags to enable/disable literal property detection (e.g., allowLiteralOnly).

Returns a TestCollection (an array of Test objects).

Documentation

For more detailed guides, see:

• Testing with Classes
• Testing with Objects
• Testing with Pure Functions
• Grouping with Module Exports

License

ISC

Changelog

1.0.0-beta.17

• Updated cjs bundle to use esbuild