test: add end-to-end tests

This commit adds end-to-end tests using generated fixtures.
For each fixture, there are multiple entry points. Coverage is first collected when running each entry point in its own Node process, then when running all of them in the same process.

The end-to-end tests check that merging the coverages from the individual entry points returns the coverage of the combined run.

The library currently fails these tests: I believe that it indicates bugs in the current implementation.

This commit also improves coverage (see bcoe#2).

Author: demurgos

package.json

@@ -4,7 +4,8 @@
   "description": "merge together two V8 coverage reports",
   "main": "index.js",
   "scripts": {
-    "test": "c8 --reporter=html --reporter=text mocha test.js",
+    "pretest": "node ./test/fixtures/generate-fixtures.js",
+    "test": "c8 --reporter=html --reporter=text mocha test",
     "coverage": "c8 --reporter=text-lcov mocha test.js | coveralls",
     "posttest": "standard",
     "release": "standard-version"
@@ -16,6 +17,7 @@
     "chai": "^4.1.2",
     "coveralls": "^3.0.2",
     "mocha": "^5.2.0",
+    "rimraf": "^2.6.2",
     "standard": "^12.0.1",
     "standard-version": "^4.4.0"
   },

test/end-to-end.spec.js

@@ -0,0 +1,50 @@
+/* global it, describe */
+
+const chai = require('chai')
+const fs = require('fs')
+const path = require('path')
+const merge = require('../index')
+
+const FIXTURES_DIR = path.join(__dirname, 'fixtures')
+const COV_RE = /^cov\.(.+)\.json$/
+
+describe('end-to-end', () => {
+  for (const fixture of getFixtures()) {
+    const {input, expected} = readFixture(fixture)
+
+    it(fixture, () => {
+      let actual = input.slice(1).reduce((acc, cov) => merge(acc, cov), input[0])
+      chai.assert.deepEqual(actual, expected)
+    })
+  }
+})
+
+function getFixtures () {
+  return fs.readdirSync(FIXTURES_DIR)
+    .filter((child) => fs.statSync(path.join(FIXTURES_DIR, child)).isDirectory())
+}
+
+function readFixture (name) {
+  const dir = path.join(FIXTURES_DIR, name)
+
+  const input = []
+  let expected
+
+  for (const child of fs.readdirSync(dir)) {
+    const match = COV_RE.exec(child)
+    if (match === null) {
+      continue
+    }
+    const data = JSON.parse(fs.readFileSync(path.join(dir, child), {encoding: 'UTF-8'}))
+    if (match[1] === 'all') {
+      expected = data
+    } else {
+      input.push(data)
+    }
+  }
+
+  if (input.length === 0 || expected === undefined) {
+    throw new Error(`Invalid fixture: ${dir}`)
+  }
+  return {input, expected}
+}

test/fixtures/.gitignore

@@ -0,0 +1,3 @@
+cov.*.json
+cov-main.*.js/
+main.all.js

test/fixtures/generate-fixtures.js

@@ -0,0 +1,127 @@
+const cp = require('child_process')
+const fs = require('fs')
+const path = require('path')
+const rimraf = require('rimraf')
+
+const SIMPLE_MAIN_RE = /^main\.\d+\.m?js$/
+const MAIN_RE = /^main\.(.+)\.m?js$/
+const MAIN_ALL = 'main.all.js'
+
+/**
+ * Generates fixtures
+ *
+ * Each fixture is a directory with a `lib.js` file and a few `main.X.js`
+ * files where `X` is an integer.
+ * For each main file, it will generate a `cov.X.json` file containing coverage
+ * for `lib.mjs` when using the corresponding main as the entry point.
+ * It also generates a `cov.all.json` obtained by executing (importing) all
+ * the entry points.
+ *
+ * Merging all the `cov.X.json` coverages should result in `cov.all.json`.
+ */
+async function main () {
+  for (const fixtureName of getFixtures()) {
+    await generateFixture(fixtureName)
+  }
+}
+
+function getFixtures () {
+  return fs.readdirSync(__dirname)
+    .filter((child) => fs.statSync(path.join(__dirname, child)).isDirectory())
+}
+
+async function generateFixture (name) {
+  const dir = path.join(__dirname, name)
+  const simpleMains = getSimpleMains(dir)
+  const mainAll = generateMainAll(simpleMains)
+  await fs.promises.writeFile(path.join(dir, MAIN_ALL), mainAll)
+  for (const simpleMain of [...simpleMains, MAIN_ALL]) {
+    const id = MAIN_RE.exec(simpleMain)[1]
+    const libCoverage = await getLibCoverage(dir, simpleMain)
+    await fs.promises.writeFile(path.join(dir, `cov.${id}.json`), JSON.stringify(libCoverage, null, 2))
+  }
+}
+
+function getSimpleMains (dir) {
+  return fs.readdirSync(dir)
+    .filter((child) => SIMPLE_MAIN_RE.test(child))
+    .sort((a, b) => {
+      a = parseInt(MAIN_RE.exec(a)[1])
+      b = parseInt(MAIN_RE.exec(b)[1])
+      return a - b
+    })
+}
+
+function generateMainAll (mains) {
+  return [
+    '// DO NOT EDIT: generated by `generate-fixtures.js`',
+    'const lib = require.resolve(\'./lib.js\')',
+    'function main () {',
+    ...mains.map(main => `  require(${JSON.stringify(`./${main}`)})\n  delete require.cache[lib]`),
+    '}',
+    'main()',
+    '',
+  ].join('\n')
+}
+
+async function getLibCoverage (dir, main) {
+  const covDirName = `cov-${main}`
+  const covDir = path.join(dir, covDirName)
+  await rmDir(covDir)
+  await spawnWithCoverage(dir, main, covDir)
+  const coverages = await readCoverage(covDir)
+  await rmDir(covDir)
+  const urlEnd = path.join('test', 'fixtures', path.basename(dir), 'lib.js')
+  for (const coverage of coverages) {
+    if (coverage.url.endsWith(urlEnd)) {
+      return {
+        scriptId: '1',
+        url: path.posix.join('/', 'test', 'fixtures', path.basename(dir), 'lib.js'),
+        functions: coverage.functions
+      }
+    }
+  }
+  throw new Error(`Coverage not found for \`lib.js\` for ${path.join(dir, main)}`)
+}
+
+async function spawnWithCoverage (dir, main, covDir) {
+  return new Promise((resolve, reject) => {
+    const proc = cp.spawn(
+      process.execPath,
+      [main],
+      {
+        cwd: dir,
+        env: {NODE_V8_COVERAGE: covDir},
+      },
+    )
+    proc.once('close', (code, signal) => {
+      if (code === 0) {
+        resolve()
+      } else {
+        reject(new Error(`Non-zero return code for: ${path.join(dir, main)}`))
+      }
+    })
+  })
+}
+
+async function rmDir (dir) {
+  return new Promise((resolve, reject) => {
+    rimraf(dir, (err) => {
+      if (err !== null) {
+        reject(err)
+      } else {
+        resolve()
+      }
+    })
+  })
+}
+
+async function readCoverage (covDir) {
+  const covChildren = fs.readdirSync(covDir)
+  if (covChildren.length !== 1) {
+    throw new Error(`Expected a single file in: ${covDir}`)
+  }
+  return JSON.parse(await fs.promises.readFile(path.join(covDir, covChildren[0]), {encoding: 'UTF-8'})).result
+}
+
+main()

test/fixtures/hello-world/lib.js

@@ -0,0 +1,3 @@
+module.exports = function () {
+  console.log('Hello, World!')
+}

test/fixtures/hello-world/main.0.js

@@ -0,0 +1,3 @@
+const lib = require('./lib')
+
+lib()

test/fixtures/hello-world/main.1.js

@@ -0,0 +1,3 @@
+const lib = require('./lib')
+
+lib()

test/fixtures/if/lib.js

@@ -0,0 +1,21 @@
+module.exports = function (test) {
+  if (test) {
+    console.log('a')
+  } else {
+    console.log('b')
+  }
+
+  if (!test) {
+    console.log('c')
+  } else {
+    console.log('d')
+  }
+
+  if (test) {
+    console.log('e')
+  }
+
+  if (!test) {
+    console.log('f')
+  }
+}

test/fixtures/if/main.0.js

@@ -0,0 +1,3 @@
+const lib = require('./lib')
+
+lib(true)

test/fixtures/if/main.1.js

@@ -0,0 +1,3 @@
+const lib = require('./lib')
+
+lib(false)

test.js test/test.spec.js

@@ -1,6 +1,6 @@
 /* global it, describe */
 
-const merge = require('./')
+const merge = require('../index')
 
 require('chai').should()