How to use the yeoman-generator.test.assertFile function in yeoman-generator

it('public/index.html should provide first config during development', function () {
    helpers.assertFile('public/index.html', /baseUrl: '..\/js'/);
    helpers.assertFile('public/index.html', /data-main="..\/require-config"/);
  });
  it('test/index.html should provide first config during development', function () {

ractive.run([], function () {
        helpers.assertFile(expected);

        done();
      });
    });

this.view.run({}, function () {
        helpers.assertFile([
          'client/views/testview.html',
          'client/views/testview.coffee'
        ]);
        done();
      });
    });

this.app.run({}, function () {
      helpers.assertFile(expected);
      done();
    });
  });

this.app.run({}, function () {
      helpers.assertFile(expected);
      done();
    });
  });

this.controller.run({}, function () {
      helpers.assertFiles( JS_FILES_GENERATED_BY_CONTROLLER_SUBGEN );
      helpers.assertFile('app/scripts/controllers/users_controller.js', /UsersController/);
      helpers.assertFile('app/scripts/routes/users_route.js', /UsersRoute/);
      done();
    });
  });

this.app.run({}, function () {
      helpers.assertFile(expected);
      done();
    });
  });

this.app.run({}, function () {
            helpers.assertFile(expected);
            done();
        });
    });

this.app.run({}, function () {
      helpers.assertFile(expected);
      done();
    });
  });