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Python · testing

conditional-assertion-in-test

python:conditional-assertion-in-test

Tests should guarantee that at least one assertion runs on every execution path.

Code
SARJ065
Default
error
Fix
none
Languages
python

Why

Assertions confined to optional branches or loops let tests pass when a branch is skipped or a collection is empty.

Fix

Add an unconditional assertion, assert collection size before iterating, or make every branch assert or fail.

Before / after

Executed by this rule’s unit tests.

Before

Assertion may never run

tests/test_rows.py · focus
def test_rows():
    rows = fetch()
    for row in rows:
        assert row.id > 0

After

Test first asserts the collection size

tests/test_rows.py · focus
def test_rows():
    rows = fetch()
    assert len(rows) == 3
    for row in rows:
        assert row.id > 0

Limits

  • Only collected tests are analyzed.
  • Exhaustive branches and explicit failure paths count as guaranteed checks.