Add PT017 and PT019 docs (#6115)

crates/ruff/src/rules/flake8_pytest_style/rules/assertion.rs

@@ -69,6 +69,34 @@ impl Violation for PytestCompositeAssertion {
     }
 }
 
+/// ## What it does
+/// Checks for `assert` statements in `except` clauses.
+///
+/// ## Why is this bad?
+/// When testing for exceptions, `pytest.raises()` should be used instead of
+/// `assert` statements in `except` clauses, as it's more explicit and
+/// idiomatic. Further, `pytest.raises()` will fail if the exception is _not_
+/// raised, unlike the `assert` statement.
+///
+/// ## Example
+/// ```python
+/// def test_foo():
+///     try:
+///         1 / 0
+///     except ZeroDivisionError as e:
+///         assert e.args
+/// ```
+///
+/// Use instead:
+/// ```python
+/// def test_foo():
+///     with pytest.raises(ZeroDivisionError) as exc_info:
+///         1 / 0
+///     assert exc_info.value.args
+/// ```
+///
+/// ## References
+/// - [API Reference: `pytest.raises`](https://docs.pytest.org/en/latest/reference/reference.html#pytest-raises)
 #[violation]
 pub struct PytestAssertInExcept {
     name: String,

crates/ruff/src/rules/flake8_pytest_style/rules/fixture.rs

@@ -129,6 +129,47 @@ impl Violation for PytestIncorrectFixtureNameUnderscore {
     }
 }
 
+/// ## What it does
+/// Checks for `pytest` test functions that should be decorated with
+/// `@pytest.mark.usefixtures`.
+///
+/// ## Why is this bad?
+/// In `pytest`, fixture injection is used to activate fixtures in a test
+/// function.
+///
+/// Fixtures can be injected either by passing them as parameters to the test
+/// function, or by using the `@pytest.mark.usefixtures` decorator.
+///
+/// If the test function depends on the fixture being activated, but does not
+/// use it in the test body or otherwise rely on its return value, prefer
+/// the `@pytest.mark.usefixtures` decorator, to make the dependency explicit
+/// and avoid the confusion caused by unused arguments.
+///
+/// ## Example
+/// ```python
+/// @pytest.fixture
+/// def _patch_something():
+///     ...
+///
+///
+/// def test_foo(_patch_something):
+///     ...
+/// ```
+///
+/// Use instead:
+/// ```python
+/// @pytest.fixture
+/// def _patch_something():
+///     ...
+///
+///
+/// @pytest.mark.usefixtures("_patch_something")
+/// def test_foo():
+///     ...
+/// ```
+///
+/// ## References
+/// - [API Reference: `pytest.mark.usefixtures`](https://docs.pytest.org/en/latest/reference/reference.html#pytest-mark-usefixtures)
 #[violation]
 pub struct PytestFixtureParamWithoutValue {
     name: String,