Introducing SafeTest: A Novel Strategy to Entrance Finish Testing | by Netflix Know-how Weblog
On this submit, we’re excited to introduce SafeTest, a revolutionary library that provides a contemporary perspective on Finish-To-Finish (E2E) assessments for web-based Consumer Interface (UI) functions.
Historically, UI assessments have been performed via both unit testing or integration testing (additionally known as Finish-To-Finish (E2E) testing). Nonetheless, every of those strategies presents a novel trade-off: it’s a must to select between controlling the check fixture and setup, or controlling the check driver.
As an illustration, when utilizing react-testing-library, a unit testing resolution, you keep full management over what to render and the way the underlying companies and imports ought to behave. Nonetheless, you lose the flexibility to work together with an precise web page, which may result in a myriad of ache factors:
- Problem in interacting with complicated UI parts like <Dropdown /> parts.
- Incapacity to check CORS setup or GraphQL calls.
- Lack of visibility into z-index points affecting click-ability of buttons.
- Advanced and unintuitive authoring and debugging of assessments.
Conversely, utilizing integration testing instruments like Cypress or Playwright supplies management over the web page, however sacrifices the flexibility to instrument the bootstrapping code for the app. These instruments function by remotely controlling a browser to go to a URL and work together with the web page. This method has its personal set of challenges:
- Problem in making calls to another API endpoint with out implementing customized community layer API rewrite guidelines.
- Incapacity to make assertions on spies/mocks or execute code throughout the app.
- Testing one thing like darkish mode entails clicking the theme switcher or understanding the localStorage mechanism to override.
- Incapacity to check segments of the app, for instance if a element is just seen after clicking a button and ready for a 60 second timer to countdown, the check might want to run these actions and will likely be no less than a minute lengthy.
Recognizing these challenges, options like E2E Element Testing have emerged, with choices from Cypress and Playwright. Whereas these instruments try to rectify the shortcomings of conventional integration testing strategies, they produce other limitations resulting from their structure. They begin a dev server with bootstrapping code to load the element and/or setup code you need, which limits their capability to deal with complicated enterprise functions that may have OAuth or a fancy construct pipeline. Furthermore, updating TypeScript utilization may break your assessments till the Cypress/Playwright crew updates their runner.
SafeTest goals to deal with these points with a novel method to UI testing. The principle thought is to have a snippet of code in our application bootstrapping stage that injects hooks to run our tests (see the How Safetest Works sections for more information on what that is doing). Word that how this works has no measurable affect on the common utilization of your app since SafeTest leverages lazy loading to dynamically load the assessments solely when working the assessments (within the README instance, the assessments aren’t within the manufacturing bundle in any respect). As soon as that’s in place, we are able to use Playwright to run common assessments, thereby attaining the best browser management we would like for our assessments.
This method additionally unlocks some thrilling options:
- Deep linking to a selected check without having to run a node check server.
- Two-way communication between the browser and check (node) context.
- Entry to all of the DX options that include Playwright (excluding those that include @playwright/check).
- Video recording of assessments, hint viewing, and pause web page performance for making an attempt out totally different web page selectors/actions.
- Means to make assertions on spies within the browser in node, matching snapshot of the decision throughout the browser.
SafeTest is designed to really feel acquainted to anybody who has performed UI assessments earlier than, because it leverages the very best elements of present options. Right here’s an instance of find out how to check a complete utility:
import { describe, it, anticipate } from 'safetest/jest';
import { render } from 'safetest/react';describe('my app', () => {
it('masses the principle web page', async () => {
const { web page } = await render();
await anticipate(web page.getByText('Welcome to the app')).toBeVisible();
anticipate(await web page.screenshot()).toMatchImageSnapshot();
});
});
We will simply as simply check a selected element
import { describe, it, anticipate, browserMock } from 'safetest/jest';
import { render } from 'safetest/react';describe('Header element', () => {
it('has a standard mode', async () => {
const { web page } = await render(<Header />);
await anticipate(web page.getByText('Admin')).not.toBeVisible();
});
it('has an admin mode', async () => {
const { web page } = await render(<Header admin={true} />);
await anticipate(web page.getByText('Admin')).toBeVisible();
});
it('calls the logout handler when signing out', async () => {
const spy = browserMock.fn();
const { web page } = await render(<Header handleLogout={spy} />);
await web page.getByText('logout').click on();
anticipate(await spy).toHaveBeenCalledWith();
});
});
SafeTest makes use of React Context to permit for worth overrides throughout assessments. For an instance of how this works, let’s assume we’ve got a fetchPeople operate utilized in a element:
import { useAsync } from 'react-use';
import { fetchPerson } from './api/particular person';export const Folks: React.FC = () => {
const { information: folks, loading, error } = useAsync(fetchPeople);
if (loading) return <Loader />;
if (error) return <ErrorPage error={error} />;
return <Desk information={information} rows=[...] />;
}
We will modify the Folks element to make use of an Override:
import { fetchPerson } from './api/particular person';
+import { createOverride } from 'safetest/react';+const FetchPerson = createOverride(fetchPerson);
export const Folks: React.FC = () => {
+ const fetchPeople = FetchPerson.useValue();
const { information: folks, loading, error } = useAsync(fetchPeople);
if (loading) return <Loader />;
if (error) return <ErrorPage error={error} />;
return <Desk information={information} rows=[...] />;
}
Now, in our check, we are able to override the response for this name:
const pending = new Promise(r => { /* Do nothing */ });
const resolved = [{name: 'Foo', age: 23], {title: 'Bar', age: 32]}];
const error = new Error('Whoops');describe('Folks', () => {
it('has a loading state', async () => {
const { web page } = await render(
<FetchPerson.Override with={() => () => pending}>
<Folks />
</FetchPerson.Override>
);
await anticipate(web page.getByText('Loading')).toBeVisible();
});
it('has a loaded state', async () => {
const { web page } = await render(
<FetchPerson.Override with={() => async () => resolved}>
<Folks />
</FetchPerson.Override>
);
await anticipate(web page.getByText('Consumer: Foo, title: 23')).toBeVisible();
});
it('has an error state', async () => {
const { web page } = await render(
<FetchPerson.Override with={() => async () => { throw error }}>
<Folks />
</FetchPerson.Override>
);
await anticipate(web page.getByText('Error getting customers: "Whoops"')).toBeVisible();
});
});
The render operate additionally accepts a operate that will likely be handed the preliminary app element, permitting for the injection of any desired parts anyplace within the app:
it('has a folks loaded state', async () => {
const { web page } = await render(app =>
<FetchPerson.Override with={() => async () => resolved}>
{app}
</FetchPerson.Override>
);
await anticipate(web page.getByText('Consumer: Foo, title: 23')).toBeVisible();
});
With overrides, we are able to write complicated check circumstances resembling making certain a service technique which mixes API requests from /foo, /bar, and /baz, has the proper retry mechanism for simply the failed API requests and nonetheless maps the return worth accurately. So if /bar takes 3 makes an attempt to resolve the tactic will make a complete of 5 API calls.
Overrides aren’t restricted to simply API calls (since we are able to use additionally use page.route), we are able to additionally override particular app stage values like characteristic flags or altering some static worth:
+const UseFlags = createOverride(useFlags);
export const Admin = () => {
+ const useFlags = UseFlags.useValue();
const { isAdmin } = useFlags();
if (!isAdmin) return <div>Permission error</div>;
// ...
}+const Language = createOverride(navigator.language);
export const LanguageChanger = () => {
- const language = navigator.language;
+ const language = Language.useValue();
return <div>Present language is { language } </div>;
}
describe('Admin', () => {
it('works with admin flag', async () => {
const { web page } = await render(
<UseIsAdmin.Override with={oldHook => {
const oldFlags = oldHook();
return { ...oldFlags, isAdmin: true };
}}>
<MyComponent />
</UseIsAdmin.Override>
);
await anticipate(web page.getByText('Permission error')).not.toBeVisible();
});
});
describe('Language', () => {
it('shows', async () => {
const { web page } = await render(
<Language.Override with={previous => 'abc'}>
<MyComponent />
</Language.Override>
);
await anticipate(web page.getByText('Present language is abc')).toBeVisible();
});
});
Overrides are a robust characteristic of SafeTest and the examples right here solely scratch the floor. For extra data and examples, seek advice from the Overrides section on the README.
SafeTest comes out of the field with highly effective reporting capabilities, resembling automated linking of video replays, Playwright hint viewer, and even deep link directly to the mounted tested component. The SafeTest repo README hyperlinks to all of the example apps in addition to the reports
Many massive companies want a type of authentication to make use of the app. Usually, navigating to localhost:3000 simply leads to a perpetually loading web page. You must go to a unique port, like localhost:8000, which has a proxy server to test and/or inject auth credentials into underlying service calls. This limitation is likely one of the fundamental causes that Cypress/Playwright Element Checks aren’t appropriate to be used at Netflix.
Nonetheless, there’s often a service that may generate check customers whose credentials we are able to use to log in and work together with the applying. This facilitates creating a light-weight wrapper round SafeTest to robotically generate and assume that check person. As an illustration, right here’s principally how we do it at Netflix:
import { setup } from 'safetest/setup';
import { createTestUser, addCookies } from 'netflix-test-helper';kind Setup = Parameters<typeof setup>[0] & {
extraUserOptions?: UserOptions;
};
export const setupNetflix = (choices: Setup) => {
setup({
...choices,
hooks: { beforeNavigate: [async page => addCookies(page)] },
});
beforeAll(async () => {
createTestUser(choices.extraUserOptions)
});
};
After setting this up, we merely import the above package deal rather than the place we’d have used safetest/setup.
Whereas this submit targeted on how SafeTest works with React, it’s not restricted to simply React. SafeTest additionally works with Vue, Svelte, Angular, and even can run on NextJS or Gatsby. It additionally runs utilizing both Jest or Vitest based mostly on which check runner your scaffolding began you off with. The examples folder demonstrates find out how to use SafeTest with totally different tooling combos, and we encourage contributions so as to add extra circumstances.
At its core, SafeTest is an clever glue for a check runner, a UI library, and a browser runner. Although the commonest utilization at Netflix employs Jest/React/Playwright, it’s simple so as to add extra adapters for different choices.
SafeTest is a robust testing framework that’s being adopted inside Netflix. It permits for simple authoring of assessments and supplies complete studies when and the way any failures occurred, full with hyperlinks to view a playback video or manually run the check steps to see what broke. We’re excited to see the way it will revolutionize UI testing and sit up for your suggestions and contributions.
