While we might never be able to have 100% of our code strict, we can at
the very least do it for all of our tests. This ensures that our tests
are using our API with the types as intended by the test author, and not
silently be cast to what our API requires.
See issue #2331. Timestamp is expected in format yyyy-mm-dd (plus other information), with the expectation that month and day are 2 digits zero-filled on the left if needed. The user's file instead used a space rather than zero as filler. Although I don't know how the unexpected timestamp was created, it was easy enough to alter the timestamp in an otherwise normal spreadsheet, and use that file as a test case.