Thanks for writing tests! Here's a quick run-down on our current setup.
- Add a unit test to
packages/*/src/TheUnitInQuestion/TheUnitInQuestion.test.js
or an integration testpackages/*/test/
. - Run
pnpm t TheUnitInQuestion
. - Implement the tested behavior
- Open a PR once the test passes or if you want somebody to review your work
For all unit tests, please use the return value from @mui/internal-test-utils/createRenderer
.
It prepares the test suite and returns a function with the same interface as
render
from @testing-library/react
.
describe('test suite', () => {
const { render } = createRenderer();
test('first', () => {
render(<input />);
});
});
For new tests please use expect
from the BDD testing approach. Prefer to use as expressive matchers as possible. This keeps
the tests readable, and, more importantly, the message if they fail as descriptive as possible.
In addition to the core matchers from chai
we also use matchers from chai-dom
.
Deciding where to put a test is (like naming things) a hard problem:
- When in doubt, put the new test case directly in the unit test file for that component, for example
packages/mui-material/src/Button/Button.test.js
. - If your test requires multiple components from the library create a new integration test.
- If you find yourself using a lot of
data-testid
attributes or you're accessing a lot of styles consider adding a component (that doesn't require any interaction) totest/regressions/tests/
, for exampletest/regressions/tests/List/ListWithSomeStyleProp
- If you have to dispatch and compose many different DOM events prefer end-to-end tests (Checkout the end-to-end testing readme for more information.)
By default, our test suite fails if any test recorded console.error
or console.warn
calls that are unexpected.
The failure message includes the full test name (suite names + test name). This should help locating the test in case the top of the stack can't be read due to excessive error messages. The error includes the logged message as well as the stacktrace of that message.
You can explicitly expect no console calls for when you're adding a regression test.
This makes the test more readable and properly fails the test in watchmode if the test had unexpected console
calls.
If you add a new warning via console.error
or console.warn
you should add tests that expect this message.
For tests that expect a call you can use our custom toWarnDev
or toErrorDev
matchers.
The expected messages must be a subset of the actual messages and match the casing.
The order of these messages must match as well.
Example:
function SomeComponent({ variant }) {
if (process.env.NODE_ENV !== 'production') {
if (variant === 'unexpected') {
console.error("That variant doesn't make sense.");
}
if (variant !== undefined) {
console.error('`variant` is deprecated.');
}
}
return <div />;
}
expect(() => {
render(<SomeComponent variant="unexpected" />);
}).toErrorDev(["That variant doesn't make sense.", '`variant` is deprecated.']);
function SomeComponent({ variant }) {
if (process.env.NODE_ENV !== 'production') {
if (variant === 'unexpected') {
console.error("That variant doesn't make sense.");
}
if (variant !== undefined) {
console.error('`variant` is deprecated.');
}
}
return <div />;
}
expect(() => {
render(<SomeComponent />);
}).not.toErrorDev();
We uses a wide range of tests approach as each of them comes with a different trade-off, mainly completeness vs. speed.
If you want to debug tests with the, for example Chrome inspector (chrome://inspect) you can run pnpm t <testFilePattern> --debug
.
Note that the test will not get executed until you start code execution in the inspector.
We have a dedicated task to use VSCode's integrated debugger to debug the currently opened test file. Open the test you want to run and press F5 (launch "Test Current File").
To run all of the unit and integration tests run pnpm test:unit
If you want to grep
for certain tests add -g STRING_TO_GREP
though for development we recommend pnpm t <testFilePattern>
.
pnpm t <testFilePattern>
First, we have the unit test suite.
It uses mocha and a thin wrapper around @testing-library/react
.
Here is an example with the Dialog
component.
Next, we have the integration tests. They are mostly used for components that
act as composite widgets like Select
or Menu
.
Here is an example with the Menu
component.
pnpm test:coverage:html
When running this command you should get under coverage/index.html
a full coverage report in HTML format. This is created using Istanbul's HTML reporter and gives good data such as line, branch and function coverage.
pnpm test:karma
Testing the components at the React level isn't enough; we need to make sure they will behave as expected with a real DOM. To solve that problem we use Karma, which is almost a drop-in replacement of jsdom. Our tests run on different browsers to increase the coverage:
- Headless Chrome
- Headless Firefox
- Chrome, Safari, and Edge thanks to BrowserStack
In development mode, if pnpm test:karma
fails with this error "Cannot start ChromeHeadless. Can not find the binary", you can solve it by installing the missing headless browsers: pnpm playwright install --with-deps
.
We only use BrowserStack for non-PR commits to save resources. BrowserStack rarely reports actual issues so we only use it as a stop-gap for releases not merges.
To force a run of BrowserStack on a PR you have to run the pipeline with browserstack-force
set to true
.
For example, you've opened a PR with the number 64209 and now after everything is green you want to make sure the change passes all browsers:
curl --request POST \
--url https://circleci.com/api/v2/project/gh/mui/material-ui/pipeline \
--header 'content-type: application/json' \
--header 'Circle-Token: $CIRCLE_TOKEN' \
--data-raw '{"branch":"pull/64209/head","parameters":{"browserstack-force":true}}'
In the end, components are going to be used in a real browser. The DOM is just one dimension of that environment, so we also need to take into account the rendering engine.
Check out the visual regression testing readme for more information.
Checkout the end-to-end testing readme for more information.
When working on the visual regression tests you can run pnpm test:regressions:dev
in the background to constantly rebuild the views used for visual regression testing.
To actually take the screenshots you can then run pnpm test:regressions:run
.
You can pass the same arguments as you could to mocha
.
For example, pnpm test:regressions:run --watch --grep "docs-system-basic"
to take new screenshots of every demo in docs/src/pages/system/basic
.
You can view the screenshots in test/regressions/screenshots/chrome
.
Alternatively, you might want to open http://localhost:5001
(while pnpm test:regressions:dev
is running) to view individual views separately.
Our tests also explicitly document which parts of the queried element are included in the accessibility (a11y) tree and which are excluded. This check is fairly expensive which is why it is disabled when tests are run locally by default. The rationale being that in almost all cases including or excluding elements from a query-set depending on their a11y-tree membership makes no difference.
The queries where this does make a difference explicitly include checking for a11y tree inclusion, for example getByRole('button', { hidden: false })
(see byRole documentation for more information).
To see if your test (test:karma
or test:unit
) behaves the same between CI and local environment, set the environment variable CI
to 'true'
.
Not considering a11y tree exclusion is a common cause of "Unable to find an accessible element with the role" or "Found multiple elements with the role".
We have a dedicated CI task that profiles our core test suite.
Since this task is fairly expensive and not relevant to most day-to-day work it has to be started manually.
The CircleCI docs explain how to start a pipeline manually in detail.
Example:
With an environment variable $CIRCLE_TOKEN
containing a CircleCI personal access token.
The following command triggers the profile
workflow for the pull request #24289.
curl --request POST \
--url https://circleci.com/api/v2/project/gh/mui/material-ui/pipeline \
--header 'content-type: application/json' \
--header 'Circle-Token: $CIRCLE_TOKEN' \
--data-raw '{"branch":"pull/24289/head","parameters":{"workflow":"profile"}}'
To analyze this profile run you can use https://mui-dashboard.netlify.app/test-profile/:job-number.
To find out the job number you can start with the response of the previous CircleCI API request which includes the created pipeline id.
You then have to search in the CircleCI UI for the job number of test_profile
that is part of the started pipeline.
The job number can be extracted from the URL of a particular CircleCI job.
For example, in https://app.circleci.com/pipelines/github/mui/material-ui/32796/workflows/23f946de-328e-49b7-9c94-bfe0a0248a12/jobs/211258 jobs/211258
points to the job number which is in this case 211258
which means you want to visit https://mui-dashboard.netlify.app/test-profile/211258 to analyze the profile.
You can check integration of different versions of React (for example different release channels or PRs to React) by running:
pnpm use-react-version <version>
Possible values for version
:
- default:
stable
(minimum supported React version) - a tag on npm, for example
next
,experimental
orlatest
- an older version, for example
^17.0.0
There are two workflows that can be triggered for any given PR manually in the CircleCI web interface:
react-next
react-17
Follow these steps:
-
Go to https://app.circleci.com/pipelines/github/mui/material-ui?branch=pull/PR_NUMBER/head and replace
PR_NUMBER
with the PR number you want to test. -
Click
Trigger Pipeline
button. -
Expand
Add parameters (optional)
and add the following parameter:Parameter type Name Value string
workflow
react-next
orreact-17
-
Click
Trigger Pipeline
button.
You can pass the same version
to our CircleCI pipeline as well:
With the following API request we're triggering a run of the default workflow in
PR #24289 for react@next
curl --request POST \
--url https://circleci.com/api/v2/project/gh/mui/material-ui/pipeline \
--header 'content-type: application/json' \
--header 'Circle-Token: $CIRCLE_TOKEN' \
--data-raw '{"branch":"pull/24289/head","parameters":{"react-version":"next"}}'