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A testcase is a page demonstrating a bug or feature. Good testcases are minimal, meaning they contain only what is needed to trigger the effect and nothing else.

How to make a testcase:

1. Start with something that demonstrates the effect you want a testcase for
2. Remove something you haven't tried removing before
3. If the feature/bug disappears, add the something back
4. Repeat 2-3 until you run out of things to remove