Method setup

packages/compiler-cli/test/ngtsc/env.ts:80–122

* Set up a new testing environment.

(files: Folder = {}, workingDir?: AbsoluteFsPath)

   * Set up a new testing environment.
   */
  static setup(files: Folder = {}, workingDir?: AbsoluteFsPath): NgtscTestEnvironment {
    const fs = getFileSystem();
    if (fs instanceof MockFileSystem) {
      fs.init(files);
    }

    const host = new AugmentedCompilerHost(fs);
    setWrapHostForTest(makeWrapHost(host));

    workingDir = workingDir ?? absoluteFrom('/');
    const env = new NgtscTestEnvironment(fs, fs.resolve('/built'), workingDir);
    fs.chdir(workingDir);

    env.write(
      absoluteFrom('/tsconfig-base.json'),
      `{
      "compilerOptions": {
        "emitDecoratorMetadata": false,
        "strictPropertyInitialization": false,
        "experimentalDecorators": true,
        "skipLibCheck": true,
        "noImplicitAny": true,
        "noEmitOnError": true,
        "strictNullChecks": true,
        "outDir": "built",
        "rootDir": ".",
        "allowJs": true,
        "declaration": true,
        "target": "es2015",
        "newLine": "lf",
        "module": "es2015",
        "moduleResolution": "bundler",
        "lib": ["es2015", "dom"],
        "typeRoots": ["node_modules/@types"]
      },
      "exclude": [
        "built"
      ]
    }`,
    );

    return env;
  }

  assertExists(fileName: string) {
    if (!this.fs.exists(this.fs.resolve(this.outDir, fileName))) {