How to use the yeoman-assert.file function in yeoman-assert

it('adds _get-media.scss and import state to sass file', function () {
			assert.file(srcPath + 'core/styles/_get-media.scss');
			assert.fileContent(srcPath + 'app.scss', /@import \"core\/styles\/get-media\"/);
		});

it('creates helper files', function () {
		assert.file(helperPath + "_grunt/csscomb.js");
		assert.file(helperPath + "task-configs/csscomb.json");
	});

it('creates helper files', function () {
		assert.file(helperPath + '_grunt/webfont.js');
		assert.file(helperPath + '_grunt/custom/iconbuilder.js');
	});

it('creates helper files', function () {
			assert.file(helperPath + '_gulp/hinting.js');
			assert.file(helperPath + 'task-configs/stylelint.config.js');
		});

it('creates helper files', function () {
		assert.file(helperPath + "_grunt/grunticon.js");
		assert.file(helperPath + "_grunt/replace.js");
	});

it('should have all npm packages in fixtures/node_modules', function() {
      var packageJson = require('./fixtures/package.json');
      var deps = Object.keys(packageJson.dependencies);
      deps = deps.concat(Object.keys(packageJson.devDependencies));
      deps = deps.map(function(dep) {
        return path.join(__dirname, 'fixtures', 'node_modules', dep);
      });
      assert.file(deps);
    });

it('creates expected files', function () {
      assert.file(expected);
      assert.fileContent(expectedContent);
    });

    .then(() => assert.file(expectedFiles));
};

.on('end', function() {
                    assert.file(expected);
                    assert.noFile([
                        'app/styles/main.css'
                    ]);
                    assert.fileContent(expectedContent);
                    done();
                });
        });

appGenerator.run({ root }, null, () => {
            const coreFiles = appFileExpectations().map((p) => path.join(root, p));
            const i18nFiles = appI18nFileExpectations().map((p) => path.join(root, p));
            const stateFiles = stateFileExpectations(appGenerator.defaultOptions.indexRouteName)
                .map((p) => path.join(root, p));

            assert.file(coreFiles);
            assert.file(i18nFiles);
            assert.file(stateFiles);

            done();
        });
    });