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# Mocha Runner
Mocha Runner is a test runner on top of mocha.
It uses `/test/TestSuites.json` and `/test/TestExpectations.json` files to run mocha tests in multiple configurations and interpret results.
## Running tests for Mocha Runner itself.
```bash
npm test
```
## Running tests using Mocha Runner
```bash
npm run build && npm run test
```
By default, the runner runs all test suites applicable to the current platform.
To pick a test suite, provide the `--test-suite` arguments. For example,
```bash
npm run build && npm run test -- --test-suite chrome-headless
```
## TestSuites.json
Define test suites via the `testSuites` attribute. `parameters` can be used in the `TestExpectations.json` to disable tests
based on parameters. The meaning for parameters is defined in `parameterDefinitions` which tell what env object corresponds
to the given parameter.
## TestExpectations.json
An expectation looks like this:
```json
{
"testIdPattern": "[accessibility.spec]",
"platforms": ["darwin", "win32", "linux"],
"parameters": ["firefox"],
"expectations": ["SKIP"]
}
```
| Field | Description | Type | Match Logic |
| --------------- | ------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------- | ----------- |
| `testIdPattern` | Defines the full name (or pattern) to match against test name | string | - |
| `platforms` | Defines the platforms the expectation is for | Array<`linux` \| `win32` \|`darwin`> | `OR` |
| `parameters` | Defines the parameters that the test has to match | Array<[ParameterDefinitions](https://github.com/puppeteer/puppeteer/blob/main/test/TestSuites.json)> | `AND` |
| `expectations` | The list of test results that are considered to be acceptable | Array<`PASS` \| `FAIL` \| `TIMEOUT` \| `SKIP`> | `OR` |
> Order of defining expectations matters. The latest expectation that is set will take president over earlier ones.
> Adding `SKIP` to `expectations` will prevent the test from running, no matter if there are other expectations.
### Using pattern in `testIdPattern`
Sometimes we want a whole group of test to run. For that we can use a
pattern to achieve.
Pattern are defined with the use of `*` (using greedy method).
Examples:
| Pattern | Description | Example Pattern | Example match |
|------------------------|---------------------------------------------------------------------------------------------|-----------------------------------|-------------------------------------------------------------------------------------------------------------------------|
| `*` | Match all tests | - | - |
| `[test.spec] *` | Matches tests for the given file | `[jshandle.spec] *` | `[jshandle] JSHandle JSHandle.toString should work for primitives` |
| `[test.spec] <text> *` | Matches tests with for a given test with a specific prefixed test (usually a describe node) | `[page.spec] Page Page.goto *` | `[page.spec] Page Page.goto should work`,<br>`[page.spec] Page Page.goto should work with anchor navigation` |
| `[test.spec] * <text>` | Matches test with a surfix | `[navigation.spec] * should work` | `[navigation.spec] navigation Page.goto should work`,<br>`[navigation.spec] navigation Page.waitForNavigation should work` |
## Updating Expectations
Currently, expectations are updated manually. The test runner outputs the
suggested changes to the expectation file if the test run does not match
expectations.
## Debugging flaky test
### Utility functions:
| Utility | Params | Description |
| ------------------------ | ------------------------------- | --------------------------------------------------------------------------------- |
| `describe.withDebugLogs` | `(title, <DescribeBody>)` | Capture and print debug logs for each test that failed |
| `it.deflake` | `(repeat, title, <itFunction>)` | Reruns the test N number of times and print the debug logs if for the failed runs |
| `it.deflakeOnly` | `(repeat, title, <itFunction>)` | Same as `it.deflake` but runs only this specific test |
### With Environment variable
Run the test with the following environment variable to wrap it around `describe.withDebugLogs`. Example:
```bash
PUPPETEER_DEFLAKE_TESTS="[navigation.spec] navigation Page.goto should navigate to empty page with networkidle0" npm run test:chrome:headless
```
It also works with [patterns](#1--this-is-my-header) just like `TestExpectations.json`
```bash
PUPPETEER_DEFLAKE_TESTS="[navigation.spec] *" npm run test:chrome:headless
```
By default the test is rerun 100 times, but you can control this as well:
```bash
PUPPETEER_DEFLAKE_RETRIES=1000 PUPPETEER_DEFLAKE_TESTS="[navigation.spec] *" npm run test:chrome:headless
```