Add tmux format tests

[arl]

No description provided.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@98153ae). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master       #1   +/-   ##
=========================================
  Coverage          ?   39.54%           
=========================================
  Files             ?        5           
  Lines             ?      177           
  Branches          ?        0           
=========================================
  Hits              ?       70           
  Misses            ?      103           
  Partials          ?        4

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