check_whitespace: add tests

See #2.
6 jobs for check_whitespace-test
Status Job ID Name Coverage
  External
failed kwrobot-branch-check

failed rust-git-hooks-megas-linux-debug

failed rust-git-hooks-megas-linux-debug

failed rust-git-hooks-megas-linux-debug

failed rust-git-hooks-megas-linux-debug

failed rust-git-hooks-megas-linux-debug

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