# conditional-in-test (SMP803)
Flags `if` statements, `match` statements and conditional expressions in test functions.
## Why is this bad?
A branching test runs a different check depending on its input or environment, so a passing run does not say which path
was verified. With one [parametrized](https://docs.pytest.org/en/stable/how-to/parametrize.html) case per path, pytest
reports each path on its own.
## Example
`tests/test_paths.py`
```python
import sys
def test_separator() -> None:
if sys.platform == "win32":
assert separator() == "\\"
else:
assert separator() == "/"
```
`tests/test_paths.py`
```python
import sys
import pytest
@pytest.mark.parametrize(
("platform", "expected"),
[
pytest.param("win32", "\\", id="windows"),
pytest.param("linux", "/", id="linux"),
],
)
def test_separator(monkeypatch: pytest.MonkeyPatch, platform: str, expected: str) -> None:
monkeypatch.setattr(sys, "platform", platform)
assert separator() == expected
```
## What it does
No fix is offered: splitting a test into cases needs knowledge of what each branch tests.
### Active on
- **`if` statements, `match` statements and conditional expressions in a test function**: a test function is a function
or method whose name starts with `test`, in a test module as defined in [test-class](SMP801.html.md). Each branch picks
which check runs.
### Example: reported
`tests/test_if.py`
```python
def test_separator() -> None:
if sys.platform == "win32":
assert separator() == "\\"
else:
assert separator() == "/"
```
`tests/test_match.py`
```python
def test_kind(kind: str) -> None:
match kind:
case "a":
assert parse(kind)
case _:
assert not parse(kind)
```
`tests/test_ternary.py`
```python
def test_length() -> None:
assert (1 if sys.platform == "win32" else 2) == separator_length()
```
### Exceptions
- **Branches inside nested functions, classes and lambdas**: they run only when that code is called, not as part of the
test’s own path.
### Example: not reported
`tests/test_nested.py`
```python
def test_callbacks() -> None:
def check(value: int) -> None:
if value:
assert value
class Helper:
def pick(self, value: int) -> int:
return 1 if value else 2
assert (lambda value: 1 if value else 2)(0) == 2
check(1)
assert Helper().pick(0) == 2
```
- **`if` clauses and conditional items in comprehensions**: they shape the items a comprehension builds, rather than
pick which check runs.
### Example: not reported
`tests/test_comprehension.py`
```python
def test_filtered(items: list[int]) -> None:
assert [item for item in items if item] == [1, 2]
```
`tests/test_comprehension_item.py`
```python
def test_labels(tags: list[str | None]) -> None:
assert [tag if tag is not None else "-" for tag in tags] == ["a", "-"]
```
## Other tools
- **[Ruff](https://github.com/astral-sh/ruff):** open issue [#11060](https://github.com/astral-sh/ruff/issues/11060).
- [Sourcery](https://sourcery.ai) flags conditionals in tests through
[no-conditionals-in-tests](https://docs.sourcery.ai/reference/refactorings/python/no-conditionals-in-tests/).