check-coverage.test.ts

import { existsSync, readFileSync } from 'node:fs'
import { normalize } from 'node:path'
import { expect, test } from 'vitest'
import libCoverage from 'istanbul-lib-coverage'
import { resolve } from 'pathe'

test('coverage exists', () => {
  expect(existsSync('./coverage')).toBe(true)
  expect(existsSync('./coverage/index.html')).toBe(true)
})

test('file coverage summary matches', () => {
  const coverageJson = JSON.parse(readFileSync('./coverage/coverage-final.json', 'utf-8'))
  const coverageMap = libCoverage.createCoverageMap(coverageJson)
  const fileCoverage = coverageMap.fileCoverageFor(normalize(resolve('./src/math.ts')))

  // There should be 1 uncovered branch and 1 uncovered function. See math.ts.
  const { branches, functions } = fileCoverage.toSummary()

  expect(branches.total - branches.covered).toBe(1)
  expect(functions.total - functions.covered).toBe(1)
})