refactor(test_shell): Use named, typed test fixtures

[tony]

Extracted from #891

[codecov[bot]]

Codecov Report

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

Comparison is base (28f4f37) 70.49% compared to head (2d57386) 70.49%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #893 +/- ## ======================================= Coverage 70.49% 70.49% ======================================= Files 25 25 Lines 1935 1935 Branches 407 407 ======================================= Hits 1364 1364 Misses 448 448 Partials 123 123 ```

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