如何在 pytest 中断言 ValueError

Question

我正在为以下函数编写 pytest 单元测试

from datetime import datetime

def validate_timestamp(timestamp):
    """Confirm that the passed in string is in the proper format %Y%m%d_%H"""
    try:
        ts = datetime.strptime(str(timestamp),'%Y%m%d_%H')
    except:
        raise ValueError("{0} must be in the format `%Y%m%d_%H".format(timestamp))
    return datetime.strftime(ts,'%Y%m%d_%H')

如何测试格式错误的时间戳？为此编写的最佳单元测试是什么？

Answer 1

运行预计会在 with 块中引发异常的代码，例如：

with pytest.raises(ValueError):
    # code

有关详细信息和选项，请阅读 https://pytest.org/en/latest/getting-started.html#assert-that-a-certain-exception-is-raised。

Answer 2

从 Python 3.1 开始，您可以使用 match 参数来匹配调用堆栈中的整个字符串或子字符串。

from datetime import datetime

def validate_timestamp(timestamp):
    """Confirm that the passed in string is in the proper format %Y%m%d_%H"""
    try:
        ts = datetime.strptime(str(timestamp),'%Y%m%d_%H')
    except:
        raise ValueError("{0} must be in the format `%Y%m%d_%H".format(timestamp))
    return datetime.strftime(ts,'%Y%m%d_%H')

def test_bad_timestamp_fails():
    with pytest.raises(ValueError, match=r"foobar must be in the format `%Y%m%d_%H"):
                       validate_timestamp("foobar")

如何在 pytest 中断言 ValueError

How to assert ValueError in pytest

python

unit-testing

pytest