即使调用了模拟，Python 模拟断言也会失败

Question

我正在使用 mock 和 pytest 在我的项目上运行多个单元测试，但我面临一个非常奇怪的错误。

在模拟中的特定测试中，我正在测试的函数中调用了一个函数，我想检查是否使用特定参数调用了该函数。 但是 mock_function.assert_called() 失败了。

为了调试它，我添加了以下几行：

    print(f"called: {str( mock_send_ano.called )}")
    print(f"call args: {str( mock_send_ano.call_args )}")
    assert mock_send_ano.assert_called()
    assert mock_send_ano.assert_called_with(expected_parameter)

在输出控制台中，我得到了：

called: True
call args: call({'msn': 'F8231', 'flight': 'V0001'})

与expected_parameter= {'msn': 'F8231', 'flight': 'V0001'}

我仍然收到此错误

AssertionError: assert None
   +  where None = <bound method NonCallableMock.assert_called of <MagicMock name='send_anomaly' id='2120318385680'>>()

这是我要测试的功能：

def retrieve_anomalies(file):
try:
    if file.split(".")[-1] == "csv" and "anomalies" in file.split("/")[3]:

        print(file)
        s3 = boto3.client("s3")
        csvfile = s3.get_object(Bucket=file.split("/")[2],Key=file.split("/")3])

        csvcontent = csvfile["Body"].read().decode("utf-8").splitlines()
        csv_data = csv.DictReader(csvcontent)

        for row in csv_data:

            anomaly = {
                "msn": row["flight_id"][:5],
                "flight": row["flight_id"][5:]
            }

            send_anomaly(anomaly)

和测试功能：

@mock.patch("boto3.client", new=mock.MagicMock())
@mock.patch("lambda_out.lambda-out.send_anomaly")
@mock.patch("csv.DictReader")
def test_ok(mock_csv_reader, mock_send_ano):
    csv_data = [
        {
            "flight_id": "F8231V0001"
        }
    ]
    mock_csv_reader.return_value = csv_data
    file = "s3://bucket/anomalies.csv"

    lambda_out.retrieve_anomalies(file)

    anomaly = {
        "msn": "F8231",
        "flight": "V0001"
    }
    print(f"called: {str( mock_send_ano.called )}")
    print(f"call args: {str( mock_send_ano.call_args )}")
    assert mock_send_ano.assert_called()
    assert mock_send_ano.assert_called_with(anomaly)

Answer 1

使用unittest.mock的assert_called方法时，您需要省略assert调用。 您的代码简单地变为：

@mock.patch("lambda_out.lambda-out.send_anomaly")
@mock.patch("csv.DictReader")
def test_ok(mock_csv_reader, mock_send_ano):
    csv_data = [
        {
            "flight_id": "F8231V0001"
        }
    ]
    mock_csv_reader.return_value = csv_data
    file = "s3://bucket/anomalies.csv"

    lambda_out.retrieve_anomalies(file)

    anomaly = {
        "msn": "F8231",
        "flight": "V0001"
    }
    print(f"called: {str( mock_send_ano.called )}")
    print(f"call args: {str( mock_send_ano.call_args )}")
    mock_send_ano.assert_called()
    mock_send_ano.assert_called_with(anomaly)