pytest assertions in Python

A test is a function whose name starts with test and whose body asserts.

def slugify(title):
    return "-".join(title.lower().split())


def test_joins_words_with_hyphens():
    assert slugify("Language Basics") == "language-basics"


def test_collapses_runs_of_space():
    assert slugify("  Two   Words ") == "two-words"


def test_leaves_a_single_word_alone():
    assert slugify("Basics") == "basics"

How it works

1. Plain assert is enough: pytest rewrites it to show both sides.
2. One behavior per test, named for what it checks.
3. No class, no setUp, no boilerplate.

Keywords and builtins used here

• assert
• def
• return
• slugify
• test_collapses_runs_of_space
• test_joins_words_with_hyphens
• test_leaves_a_single_word_alone

The run, in numbers

Lines

14

Characters to type

316

Tokens

71

Three-star pace

100 tpm

At the three-star pace of 100 tokens a minute, this run takes about 43 seconds.

Type this snippet

Step 1 of 3 in Writing tests, step 1 of 9 in Testing with pytest.

Next →