The output of the GetWindowDimensions function is hard to understand just by looking at it,
so I've added a helper function in the tests to render the window layout as text, so that
in order to create a new test you just come up with some args and paste the output as the
expected output.
This has the same downsides that any snapshot-based testing has: it's more brittle than
targeted assertions. But it is much easier to make sense of these snapshots than it is
to make sense of more fine-grained assertions, and I like the fact that these tests can
serve as documentation.
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