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clean-tests

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Clean Tests

整洁测试

T1: Insufficient Tests

T1: 测试覆盖不足

Test everything that could possibly break. Use coverage tools as a guide, not a goal.
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测试所有可能出现问题的场景。将覆盖率工具作为参考，而非目标。
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Bad - only tests happy path

不良示例 - 仅测试正常路径

def test_divide(): assert divide(10, 2) == 5
def test_divide(): assert divide(10, 2) == 5

Good - tests edge cases too

良好示例 - 同时测试边缘场景

def test_divide_normal(): assert divide(10, 2) == 5
def test_divide_by_zero(): with pytest.raises(ZeroDivisionError): divide(10, 0)
def test_divide_negative(): assert divide(-10, 2) == -5
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def test_divide_normal(): assert divide(10, 2) == 5
def test_divide_by_zero(): with pytest.raises(ZeroDivisionError): divide(10, 0)
def test_divide_negative(): assert divide(-10, 2) == -5
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T2: Use a Coverage Tool

T2: 使用覆盖率工具

Coverage tools report gaps in your testing strategy. Don't ignore them.
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覆盖率工具可报告测试策略中的漏洞，不要忽略这些结果。
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Run with coverage

结合覆盖率工具运行测试

pytest --cov=myproject --cov-report=term-missing
pytest --cov=myproject --cov-report=term-missing

Aim for meaningful coverage, not 100%

追求有意义的覆盖率，而非100%覆盖率

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T3: Don't Skip Trivial Tests

T3: 不要跳过简单测试

Trivial tests document behavior and catch regressions. They're worth more than their cost.
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简单测试可记录预期行为并捕获回归问题，其价值远高于编写成本。
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Worth having - documents expected behavior

值得编写 - 记录预期行为

def test_user_default_role(): user = User(name="Alice") assert user.role == "member"
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def test_user_default_role(): user = User(name="Alice") assert user.role == "member"
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T4: An Ignored Test Is a Question About an Ambiguity

T4: 被忽略的测试意味着存在模糊性问题

Don't use 
@pytest.mark.skip
to hide problems. Either fix the test or delete it.
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不要使用
@pytest.mark.skip
来掩盖问题。要么修复测试，要么删除它。
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Bad - hiding a problem

不良示例 - 掩盖问题

@pytest.mark.skip(reason="flaky, fix later") def test_async_operation(): ...
@pytest.mark.skip(reason="flaky, fix later") def test_async_operation(): ...

Good - either fix it or document why it's skipped

良好示例 - 要么修复，要么明确说明跳过原因

@pytest.mark.skip(reason="Requires Redis, see CONTRIBUTING.md for setup") def test_cache_invalidation(): ...
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@pytest.mark.skip(reason="Requires Redis, see CONTRIBUTING.md for setup") def test_cache_invalidation(): ...
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T5: Test Boundary Conditions

T5: 测试边界条件

Bugs congregate at boundaries. Test them explicitly.
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def test_pagination_boundaries():
    items = list(range(100))
    
    # First page
    assert paginate(items, page=1, size=10) == items[0:10]
    
    # Last page
    assert paginate(items, page=10, size=10) == items[90:100]
    
    # Beyond last page
    assert paginate(items, page=11, size=10) == []
    
    # Page zero (invalid)
    with pytest.raises(ValueError):
        paginate(items, page=0, size=10)
    
    # Empty list
    assert paginate([], page=1, size=10) == []
漏洞往往集中在边界场景，需明确测试这些场景。
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def test_pagination_boundaries():
    items = list(range(100))
    
    # 第一页
    assert paginate(items, page=1, size=10) == items[0:10]
    
    # 最后一页
    assert paginate(items, page=10, size=10) == items[90:100]
    
    # 超出最后一页
    assert paginate(items, page=11, size=10) == []
    
    # 第0页（无效）
    with pytest.raises(ValueError):
        paginate(items, page=0, size=10)
    
    # 空列表
    assert paginate([], page=1, size=10) == []

T6: Exhaustively Test Near Bugs

T6: 针对已发现漏洞的相似场景进行全面测试

When you find a bug, write tests for all similar cases. Bugs cluster.
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当发现一个漏洞时，为所有相似场景编写测试。漏洞往往会集中出现。
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Found bug: off-by-one in date calculation

发现漏洞：日期计算中的差一错误

Now test ALL date boundaries

现在测试所有日期边界场景

def test_month_boundaries(): assert last_day_of_month(2024, 1) == 31 # January assert last_day_of_month(2024, 2) == 29 # Leap year February assert last_day_of_month(2023, 2) == 28 # Non-leap February assert last_day_of_month(2024, 4) == 30 # 30-day month assert last_day_of_month(2024, 12) == 31 # December
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def test_month_boundaries(): assert last_day_of_month(2024, 1) == 31 # 一月 assert last_day_of_month(2024, 2) == 29 # 闰年二月 assert last_day_of_month(2023, 2) == 28 # 非闰年二月 assert last_day_of_month(2024, 4) == 30 # 30天的月份 assert last_day_of_month(2024, 12) == 31 # 十二月
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T7: Patterns of Failure Are Revealing

T7: 测试失败的模式具有参考价值

When tests fail, look for patterns. They often point to deeper issues.
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当测试失败时，寻找其中的模式，它们通常指向更深层次的问题。
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If all async tests fail intermittently,

如果所有异步测试都间歇性失败，

the problem isn't the tests—it's the async handling

问题不在测试本身——而是异步处理逻辑有问题

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T8: Test Coverage Patterns Can Be Revealing

T8: 测试覆盖率模式具有参考价值

Look at which code paths are untested. Often they reveal design problems.
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查看哪些代码路径未被测试，它们通常会暴露设计问题。
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If you can't easily test a function, it probably does too much

如果某个函数难以测试，它可能承担了过多职责

Refactor for testability

需重构以提升可测试性

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T9: Tests Should Be Fast

T9: 测试应快速执行

Slow tests don't get run. Keep unit tests under 100ms each.
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缓慢的测试不会被频繁运行。确保每个单元测试的执行时间在100ms以内。
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Bad - hits real database

不良示例 - 连接真实数据库

def test_user_creation(): db = connect_to_database() # Slow! user = db.create_user("Alice") assert user.name == "Alice"
def test_user_creation(): db = connect_to_database() # 速度慢！ user = db.create_user("Alice") assert user.name == "Alice"

Good - uses mock or in-memory

良好示例 - 使用模拟或内存数据库

def test_user_creation(): db = InMemoryDatabase() user = db.create_user("Alice") assert user.name == "Alice"
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def test_user_creation(): db = InMemoryDatabase() user = db.create_user("Alice") assert user.name == "Alice"
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Test Organization

测试组织规范

F.I.R.S.T. Principles

F.I.R.S.T. 原则

  • Fast: Tests should run quickly
  • Independent: Tests shouldn't depend on each other
  • Repeatable: Same result every time, any environment
  • Self-Validating: Pass or fail, no manual inspection
  • Timely: Written before or with the code, not after
  • Fast：测试应快速运行
  • Independent：测试之间不应存在依赖关系
  • Repeatable：在任何环境下，每次运行都能得到相同结果
  • Self-Validating：通过或失败，无需人工检查
  • Timely：在代码编写之前或同时编写测试，而非之后

One Concept Per Test

每个测试仅验证一个概念

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Bad - testing multiple things

不良示例 - 同时测试多个内容

def test_user(): user = User("Alice", "alice@example.com") assert user.name == "Alice" assert user.email == "alice@example.com" assert user.is_valid() user.activate() assert user.is_active
def test_user(): user = User("Alice", "alice@example.com") assert user.name == "Alice" assert user.email == "alice@example.com" assert user.is_valid() user.activate() assert user.is_active

Good - one concept each

良好示例 - 每个测试仅验证一个概念

def test_user_stores_name(): user = User("Alice", "alice@example.com") assert user.name == "Alice"
def test_user_stores_email(): user = User("Alice", "alice@example.com") assert user.email == "alice@example.com"
def test_new_user_is_valid(): user = User("Alice", "alice@example.com") assert user.is_valid()
def test_user_can_be_activated(): user = User("Alice", "alice@example.com") user.activate() assert user.is_active
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def test_user_stores_name(): user = User("Alice", "alice@example.com") assert user.name == "Alice"
def test_user_stores_email(): user = User("Alice", "alice@example.com") assert user.email == "alice@example.com"
def test_new_user_is_valid(): user = User("Alice", "alice@example.com") assert user.is_valid()
def test_user_can_be_activated(): user = User("Alice", "alice@example.com") user.activate() assert user.is_active
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Quick Reference

快速参考

RulePrinciple
T1Test everything that could break
T2Use coverage tools
T3Don't skip trivial tests
T4Ignored test = ambiguity question
T5Test boundary conditions
T6Exhaustively test near bugs
T7Look for patterns in failures
T8Check coverage when debugging
T9Tests must be fast (<100ms)
规则原则
T1测试所有可能出现问题的场景
T2使用覆盖率工具
T3不要跳过简单测试
T4被忽略的测试 = 存在模糊性问题
T5测试边界条件
T6针对已发现漏洞的相似场景进行全面测试
T7寻找测试失败中的模式
T8调试时检查覆盖率
T9测试必须快速（<100ms）