What is the best way to specify the JSDoc types for this.field within the Mocha TestContext during the before() hook, in order to provide clarity for other it() tests as well as IntelliJ?

I am looking for IntelliJ, or a similar IDE like WebStorm or VSCode, to provide auto-complete for the fields I define in my Mocha.js before() hook within my test context. Furthermore, I want to have access to the auto-complete documentation of those fields in all of my unit tests that utilize that test context.

Let me illustrate with an example:

describe('🔥Awesome Test Code🔥', async function()
{

  /** A super expensive thing that each unit test needs. **/
  class ExpensiveThing { expensive = true; }

  /**
   * Execute this once before the first test in this describe block.
   * {@link https://mochajs.org/#hooks Mocha Hooks}
   * {@link https://mochajs.org/#global-teardown-fixtures Mocha Test Contexts}
   */
  before('the first test', async function()
  {
    // We can prepare anything we want here and set it on this
    // so that each unit test can access it when the unit test runs.
    // This is better than initializing it in the describe() block
    // because then the code would run when mocha parses the tests
    // and it would get executed even if the test is not run.
    // https://mochajs.org/#global-teardown-fixtures
    
    this.expensiveThingUsedForTheTests = new ExpensiveThing();
    //👆      ⬆️                                 ⬆️
    // ________|__________________________________|________
    // !!! I want to define the type of this field here !!!
    // ----------------------------------------------------
  });

  it('should be easy', async function(){

    this.expensiveThingUsedForTheTests.expensive = false;
    //👆      ⬆️                          ⬆️
    // ________|___________________________|_________________________
    // !!! I want this to give me auto-complete and documentation !!!
    // --------------------------------------------------------------

    assert.equal(this.expensiveThingUsedForTheTests.expensive, false, 'This was not easy!');
  });

});

However, when I press CTRL+Q on the field in IntelliJ IDEA, this is what I see instead: https://i.sstatic.net/DdXvpKm4.png

Answer №1

To effectively utilize the test context, make sure to incorporate the @typedef JSDoc tag along with the @this tag on each method associated with that context. You can also utilize the @type tag to provide documentation for the this.x field within the before() hook.

For detailed information, refer to:
JSDoc @typedef - Defines a name for the test context.
JSDoc @this - Links this to the test contexts.
JSDoc @type - Documents the field on this.x.

Here is an example to illustrate the process:

    // Use the @this JSDoc comment to specify the defined test context in the before() hook:
    /**
     * @this ThisTestContext
     */
    before('the first test', async function()
    {
        // Define the specific test context.
        // You can choose any name other than 'ThisTestContext'.

        /**
         * The context for the awesome unit tests. Utilize this.x to establish the test context.
         * <p>
         * {@link https://jsdoc.app/tags-typedef JSDoc @typedef}
         * {@link https://jsdoc.app/tags-this JSDoc @this}
         * {@link https://jsdoc.app/tags-type JSDoc @type}
         * {@link https://mochajs.org/#hooks Mocha Hooks}
         * {@link https://mochajs.org/#global-teardown-fixtures Mocha Test Contexts}
         * @typedef {object} ThisTestContext
         */

        // Add the @type JSDoc comment above the field you want to document:

        /** {@type ExpensiveThing} The expensive thing that we create once and reuse across tests. **/
        this.expensiveThingUsedForTheTests = new ExpensiveThing();
        //👆      ⬆️                                 ⬆️
        // ________|__________________________________|___________________________
        // !!! You just define this normally, plus a @type JSDoc comment above !!!
        // -----------------------------------------------------------------------
    });

    // Use the @this JSDoc comment to link this to the same test context defined in the before() hook:
    /**
     * @this ThisTestContext
     */
    it('should be easy', async function(){

        this.expensiveThingUsedForTheTests.expensive = false;
        //👆      ⬆️                          ⬆️
        // ________|___________________________|____________________
        // !!! Now all the auto-complete and documentation works !!!
        // ---------------------------------------------------------

        assert.equal(this.expensiveThingUsedForTheTests.expensive, false, 'This was much easier!');
    });

You can observe the auto-complete functionality in IntelliJ with this setup: https://i.sstatic.net/2foXq6gM.png

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