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Test Suites and Annotations.md

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describe

You can group a set of tests into a suite using describe. If you don't use describe, all of the tests in a given file as grouped in a suite automatically.

The is primarily used for organizing your tests. It's helpful because it allows you to skip or isolate a particular group of tests.

We'll cover this in a bit more depth in More on Filtering Tests, but if you provide a string after npm test or npx vitest, then Vitest will only run the rests with that string in the filename. Let's say we have two test files: math.test.ts and words.test.ts. Running npm test math will only run math.test.ts and not words.test.ts.

For example, if we ran our suite against examples/02-test-suites/math.test.ts (using npm test math --reporter="verbose" --run, just to make a point), we would see something like this:

 ✓ math.test.ts (8)
   ✓ add (2)
     ✓ should add two numbers correctly
     ✓ should not add two numbers incorrectly
   ✓ subtract (2)
     ✓ should subtract the subtrahend from the minuend
     ✓ should not subtract two numbers incorrectly
   ✓ multiply (2)
     ✓ should multiply the multiplicand by the multiplier
     ✓ should not multiply two numbers incorrectly
   ✓ divide (2)
     ✓ should multiply the multiplicand by the multiplier
     ✓ should not multiply two numbers incorrectly

Hooks

Using describe allows you to pass a name to your suite, which is helpful when you're debugging. It also gives you access to some helpful hooks:

  • beforeEach: Runs before each and every test.
  • afterEach: Runs after each and every test.
  • beforeAll: Runs at the very beginning when the suite starts.
  • afterAll: Runs after all of the tests in the suite have completed.

Annotations

These are fairly similar to what we saw with our individual tests.

describe also has some annotations that add some logic to if any when the suite should run:

  • describe.skip: Skip this suite.
  • describe.skipIf: Skip this suite if the provided value is truthy.
  • describe.only: Only run this suite (and any others that use .only as well, of course). You probably don't want to accidentally commit this. Trust me. It's embarassing.
  • describe.todo: Marks a suite as something you're going to implement later. This is helpful when you know the kinds of tests that you'll need and and want to keep track of how many you have less.
  • describe.each: Used for generating a multiple suites on based on a collection of data. We'll talk about this more in Parameterizing Tests.
  • describe.concurrent: Run all of the tests in this suite concurrently. We'll talk about this more in Parallelizing Tests.
  • describe.shuffle: Run these tests in a random order.