Function assertTransform

test/index.js:21–56

(initial, expected, opts)

  .join(EOL);

const assertTransform = async (initial, expected, opts) => {
  const transformOpts = {
    ...opts,
    // Specify filename to pick up local `.babelrc.js`
    // https://babeljs.io/docs/en/options#babelrc
    filename: initial
  };

  // Note: We trim + EOL to normalize whitespace + give readable error diffs
  // Also normalize across OS'es.
  const [actualCode, expectedCode] = await Promise.all([
    readFile(initial).then((code) => babel.transform(code, transformOpts).code),
    readFile(expected).then((buf) => buf.toString())
  ]).then((vals) => vals.map((val) => val
    .split(/\r?\n/)
    .join(EOL)
    .trim() + EOL
  ));

  const diff = jsdiff.diffLines(actualCode, expectedCode);
  // Consider no diff or newline-only diff to be "the same".
  const changes = diff.filter(({ added, removed, value }) => (added || removed) && value.trim());
  if (changes.length === 0) {
    return true;
  }

  const msg = diff
    .map((obj) => {
      if (obj.added) { return splitLines(obj, (line) => chalk `{green +${line}}`); }
      if (obj.removed) { return splitLines(obj, (line) => chalk `{red -${line}}`); }
      return splitLines(obj, (line) => chalk `{grey  ${line}}`);
    })
    .join("");

  throw new Error(chalk `{white Difference found ({green actual}, {red expected}): ${EOL}}${msg}`);
};

const getBabelOps = (pluginOps) => ({
  presets: ["@babel/preset-env"],