Question

我在单元测试中嘲笑导入的模块时遇到了麻烦。我试图使用mock模块在我的模块tracker.models中模拟PIL Image类。我知道你应该嘲笑使用它们的东西，所以我写了@mock.patch('tracker.models.Image')作为单元测试的装饰者。我正在尝试检查下载的图像是否作为PIL图像打开。模拟补丁似乎覆盖了整个Image模块。以下是我在运行测试时遇到的错误：

File "/home/ubuntu/workspace/tracker/models.py", line 40, in set_photo
    width, height = image.size
ValueError: need more than 0 values to unpack

这是我的单元测试：

test_models.py

@responses.activate
@mock.patch('tracker.models.Image')
def test_set_photo(self, mock_pil_image):
    # Initialize data
    hammer = Product.objects.get(name="Hammer")
    fake_url = 'http://www.example.com/prod.jpeg'
    fake_destination = 'Hammer.jpeg'

    # Mock successful image download using sample image. (This works fine)
    with open('tracker/tests/test_data/small_pic.jpeg', 'r') as pic:
        sample_pic_content = pic.read()
    responses.add(responses.GET, fake_url, body=sample_pic_content, status=200, content_type='image/jpeg')

    # Run the actual method
    hammer.set_photo(fake_url, fake_destination)

    # Check that it was opened as a PIL Image
    self.assertTrue(mock_pil_image.open.called,
                    "Failed to open the downloaded file as a PIL image.")

以下是它正在测试的一段代码。

跟踪器/ models.py

class Product(models.Model):
    def set_photo(self, url, filename):
        image_request_result = requests.get(url)
        image_request_result.content
        image = Image.open(StringIO(image_request_result.content))

        # Shrink photo if needed
        width, height = image.size  # Unit test fails here
        max_size = [MAX_IMAGE_SIZE, MAX_IMAGE_SIZE]
        if width > MAX_IMAGE_SIZE or height > MAX_IMAGE_SIZE:
            image.thumbnail(max_size)
        image_io = StringIO()
        image.save(image_io, format='JPEG')
        self.photo.save(filename, ContentFile(image_io.getvalue()))

Answer 1

您需要配置Image.open的返回值以包含size属性：

opened_image = mock_pil_image.open.return_value
opened_image.size = (42, 83)

现在，当您的被测函数调用Image.open时，返回的MagicMock实例将具有size属性，这是一个元组。

对于需要返回某些内容的任何其他方法或属性，您可以执行相同的操作。

opened_image参考对于测试被测功能的其他方面也很有用;您现在可以断言image.thumbnail和image.save被调用：

opened_image = mock_pil_image.open.return_value
opened_image.size = (42, 83)

# Run the actual method
hammer.set_photo(fake_url, fake_destination)

# Check that it was opened as a PIL Image
self.assertTrue(mock_pil_image.open.called,
                "Failed to open the downloaded file as a PIL image.")

self.assertTrue(opened_image.thumbnail.called)
self.assertTrue(opened_image.save.called)

这使您可以非常准确地测试缩略图大小逻辑是否正常工作，例如，无需测试PIL是否正在执行其操作;毕竟，PIL没有在这里进行测试。

Answer 2

我正在编写类似的测试，但是我的功能是使用using namespace std作为上下文管理器（Image.open）。多亏Martijn Pieters的回答和this one，我才得以将测试用于：

with Image.open(<filepath>) as img:

这个Python模拟补丁有什么问题？

2 个答案: