TestSpecification

The TestSpecification class describes what module to run as a test and its parameters.

You can only create a specification by calling createSpecification method on a test project:

const specification = project.createSpecification(
  resolve('./example.test.ts'),
  [20, 40], // optional test lines
)

createSpecification expects resolved module ID. It doesn't auto-resolve the file or check that it exists on the file system.

project

This references the TestProject that the test module belongs to.

moduleId

The ID of the module in Vite's module graph. Usually, it's an absolute file path using posix separator:

'C:/Users/Documents/project/example.test.ts' // ✅
'/Users/mac/project/example.test.ts' // ✅
'C:\\Users\\Documents\\project\\example.test.ts' // ❌

pool experimental

The pool in which the test module will run.

DANGER

It's possible to have multiple pools in a single test project with poolMatchGlob and typecheck.enabled. This means it's possible to have several specifications with the same moduleId but different pool. In Vitest 4, the project will only support a single pool, and this property will be removed.

testLines

This is an array of lines in the source code where the test files are defined. This field is defined only if the createSpecification method received an array.

Note that if there is no test on at least one of the lines, the whole suite will fail. An example of a correct testLines configuration:

script.js

const specification = project.createSpecification(
  resolve('./example.test.ts'),
  [3, 8, 9],
)

example.test.js

import { test, describe } from 'vitest'

test('verification works')

describe('a group of tests', () => { 
  // ...

  test('nested test')
  test.skip('skipped test')
})

toJSON

function toJSON(): SerializedTestSpecification

toJSON generates a JSON-friendly object that can be consumed by the Browser Mode or Vitest UI.