如何对绘制PDF图形的Python函数进行单元测试？ [英] How to unit test a Python function that draws PDF graphics?

问题描述

我正在编写一个使用Cairo图形库输出PDF文件的CAD应用程序。许多单元测试不需要实际生成PDF文件，例如计算对象的预期边界框。但是，我想确保在更改代码后生成的PDF文件看起来正确。有没有自动化的方法来做到这一点？我怎样才能尽可能自动化？我是否需要目视检查每个生成的PDF？如何在不拔头的情况下解决这个问题？

I'm writing a CAD application that outputs PDF files using the Cairo graphics library. A lot of the unit testing does not require actually generating the PDF files, such as computing the expected bounding boxes of the objects. However, I want to make sure that the generated PDF files "look" correct after I change the code. Is there an automated way to do this? How can I automate as much as possible? Do I need to visually inspect each generated PDF? How can I solve this problem without pulling my hair out?

推荐答案

您可以将PDF捕获为位图（或者至少是无损压缩的图像，然后将每个测试生成的图像与它应该看起来像的参考图像进行比较。任何差异都会被标记为测试错误。

You could capture the PDF as a bitmap (or at least a losslessly-compressed) image, and then compare the image generated by each test with a reference image of what it's supposed to look like. Any differences would be flagged as an error for the test.

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