Unit Test Patterns

Structure every unit test as Arrange-Act-Assert with one assertion concept per test, no logic in tests, and no coupling between tests.

Structure — Arrange, Act, Assert (AAA):

// Arrange — set up preconditions
// Act — call the method under test
// Assert — verify the result

Rules:

• Each test MUST have one assertion concept (not one assert — one logical concept)
• Tests MUST NOT contain logic — no if, for, try/catch, switch
• Tests SHOULD target the public API, not internals — tests should survive refactoring
• Each test MUST be independent — arrange its own state, don't rely on other tests

Naming — use descriptive names that read as specifications:

• test_parse_order_with_valid_json_returns_order
• ParseOrder_WithMissingField_ThrowsValidationError
• "returns empty list when no results match"

Change History