Convert tests from unittest to pytest

[ESadek-MO]

🧪 PyTest Conversion

This issue will be used to track the progress of the move from unittest to pytest. Progress on this has already been made on #6207.

If you notice an inaccuracy in this list, please feel free to change it!

[path/to/test/directory/]: (Link to Project View)

• [/]: (Link to Project View)
• [/experimental]: (Link to Project View)
• [/graphics]: (Link to Project View)
• [/unit]: (Link to Project View)
• [/unit/analysis]: (Link to Project View)
• [/unit/aux_factory]: (Link to Project View)
• [/unit/common]: (Link to Project View)
• [/unit/concatenate]: (Link to Project View)
• [/unit/config]: (Link to Project View)
• [/unit/constraints]: (Link to Project View)
• [/unit/coord_categorisation]: (Link to Project View)
• [/unit/coord_systems]: (Link to Project View)
• [/unit/coords]: (Link to Project View)
• [/unit/cube]: (Link to Project View)
• [/unit/data_manager]: (Link to Project View)
• [/unit/experimental]: (Link to Project View)
• [/unit/io]: (Link to Project View)
• [/unit/lazy_data]: (Link to Project View)
• [/unit/merge]: (Link to Project View)
• [/unit/pandas]: (Link to Project View)
• [/unit/plot]: (Link to Project View)
• [/unit/quickplot]: (Link to Project View)
• [/unit/representation]: (Link to Project View)
• [/unit/tests]: (Link to Project View)
• [/unit/time]: (Link to Project View)
• [/unit/util]: (Link to Project View)
• [/integration]: (Link to Project View)
• [/integration/analysis]: (Link to Project View)
• [/integration/aux_factory]: (Link to Project View)
• [/integration/concatenate]: (Link to Project View)
• [/integration/experimental]: (Link to Project View)
• [/integration/fast_load]: (Link to Project View)
• [/integration/merge]: (Link to Project View)
• [/integration/netcdf]: (Link to Project View)
• [/integration/plot]: (Link to Project View)
• [/integration/um]: (Link to Project View)
• [/unit/fileformats]: (Link to Project View)
• [/unit/fileformats/abf]: (Link to Project View)
• [/unit/fileformats/cf]: (Link to Project View)
• [/unit/fileformats/dot]: (Link to Project View)
• [/unit/fileformats/ff]: (Link to Project View)
• [/unit/fileformats/name_loaders]: (Link to Project View)
• [/unit/fileformats/nc_load_rules]: (Link to Project View)
• [/unit/fileformats/netcdf]: (Link to Project View)
• [/unit/fileformats/nimrod_load_rules]: (Link to Project View)
• [/unit/fileformats/pp]: (Link to Project View)
• [/unit/fileformats/pp_load_rules]: (Link to Project View)
• [/unit/fileformats/rules]: (Link to Project View)
• [/unit/fileformats/structured_array_identification]: (Link to Project View)
• [/unit/fileformats/um]: (Link to Project View)