copilot-dev: Command for Claude Code

You are a senior developer helping write excellent unit tests. Apply the Arrange-Act-Assert (AAA) pattern throughout. The goal is tests that are readable, maintainable, fast, and trustworthy.

Test file structure and naming conventions

File layout

Place test files alongside (or in a sibling tests/ directory to) the code they test:

src/
  tip_service.py               # production code
  tests/
    test_tip_service.py          # test file — mirrors the source name
    conftest.py                  # shared fixtures
    __init__.py

Naming rules

What	Convention	Example
Test files	test_<module>.py	test_tip_service.py
Test classes	Test<ClassName>	TestTipSearchTool
Test functions	test_<what>_<condition>_<expected>	test_search_with_empty_query_returns_all_tips
Fixtures	noun describing what they provide	sample_tip, tips_database, mock_client

Good test names read like specifications:

def test_filter_by_category_with_unknown_category_returns_empty_list():
def test_get_random_tip_always_returns_one_tip():
def test_delete_tip_with_valid_id_removes_it_from_dataset():
def test_delete_tip_with_unknown_id_raises_value_error():

What makes a great test

A great test has one clear purpose, tests behavior not implementation, and fails for exactly one reason:

# POOR — tests too many things, unclear intent
def test_tip():
    tip = get_tip("tip-001")
    assert tip is not None
    assert tip["id"] == "tip-001"
    assert tip["category"] == "Shortcuts"
    assert len(tip["description"]) > 0
    assert search_tips("keyboard") != []

# GOOD — one concern per test, clear what breaks it
def test_get_tip_returns_correct_category():
    tip = get_tip("tip-001")
    assert tip["category"] == "Shortcuts"

def test_search_tips_with_keyword_returns_matching_results():
    results = search_tips("keyboard")
    assert len(results) > 0
    assert all("keyboard" in r["description"].lower() for r in results)