testbed-public-methods.ts

get(token: any, notFoundValue: any = Injector.THROW_IF_NOT_FOUND) {
    this._initIfNeeded();
    if (token === TestBed) {
      return this;
    }
    const result = this._moduleRef.injector.get(token, UNDEFINED);
    return result === UNDEFINED ? this._compiler.injector.get(token, notFoundValue) : result;
  }

…

compileComponents(): Promise<any> {
    if (this._moduleFactory || this._instantiated) {
      return Promise.resolve(null);
    }
   const moduleType = this._createCompilerAndModule();
    return this._compiler.compileModuleAndAllComponentsAsync(moduleType)
        .then((moduleAndComponentFactories) => {
          this._moduleFactory = moduleAndComponentFactories.ngModuleFactory;
        });
  }