Fix bug in WikiProject builder frontend, add test, tweak tests

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 90.95%. Comparing base (0c6b468) to head (f47a63b).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #732 +/- ## ======================================= Coverage 90.95% 90.95% ======================================= Files 64 64 Lines 3394 3394 ======================================= Hits 3087 3087 Misses 307 307 ```

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