Allow to check outputs of tests

[EagleoutIce]

See Slice for initial x should return noting else in calls-tests for an example.

[codecov[bot]]

Codecov Report

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

Project coverage is 71.82%. Comparing base (1f92d6e) to head (2d7f746).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #799 +/- ## ======================================= Coverage 71.82% 71.82% ======================================= Files 201 201 Lines 7192 7192 Branches 1109 1109 ======================================= Hits 5166 5166 Misses 1679 1679 Partials 347 347 ```

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[EagleoutIce]

This pull request is included in v2.0.2 (see Release v2.0.2 (Fixing Control-Flow, Markdown-Exports, and Handling of Unnamed Closures)).