Structure test cases for maximum readability and maintainability by following these principles:

1. Organize each test in three distinct parts separated by blank lines:
   • Setup (arrange test fixtures)
   • Execution (run unit under test)
   • Verification (assert expected results)
2. Minimize intermediate variables - use direct assertions when possible:

Instead of:

matrix = [["cell1", "cell2"], ["cell3", "cell4"]]
expected_html = "<table><tr><td>cell1</td>...</table>"
assert utils.htmlify_matrix(matrix) == expected_html

Prefer:

assert utils.htmlify_matrix([["cell1", "cell2"], ["cell3", "cell4"]]) == (
    "<table><tr><td>cell1</td><td>cell2</td></tr>"
    "<tr><td>cell3</td><td>cell4</td></tr></table>"
)

1. Use parameterization to avoid repeated test code:

   @pytest.mark.parametrize(
    "date", ["1990-12-01", "2050-01-01T00:00:00", "2050-01-01+00:00:00"]
   )
   def test_validate_date_args_accepts_standard_formats(date):
    assert utils.validate_date_args(date)
   

2. Write meaningful assertions that clearly indicate the behavior being tested: ```python

   Weak assertion:

   assert “error” in caplog.text

Better assertion:

assert “invalid date format, expected YYYY-MM-DD” in caplog.text ```