Fix lambda syntax error in test case macros

[RedSkittleFox]

Fixed invalid lambda syntax from []() <typename T> to proper C++ syntax []<typename T>().

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.97%. Comparing base (67cc5c7) to head (cc38283).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #217   +/-   ##
=======================================
  Coverage   93.97%   93.97%           
=======================================
  Files          30       30           
  Lines        1775     1775           
=======================================
  Hits         1668     1668           
  Misses        107      107           

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[cschreib]

How did that ever work?! Thank you for spotting and fixing this. Can I ask how you happened to notice this was not right? Was it causing an issue with a particular compiler?

[RedSkittleFox]

How did that ever work?! Thank you for spotting and fixing this. Can I ask how you happened to notice this was not right? Was it causing an issue with a particular compiler?

I don't think it has ever worked. My guess is that this macro has never been properly tested. I stumbled across this whilst using GCC 15.2.

[cschreib]

I don't think it has ever worked. My guess is that this macro has never been properly tested.

Ahah yes, you're right.