Use data path and fixtures consistently

[K-Meech]

Description

What is this PR

• Bug fix
• Addition of a new feature
• Other

Why is this PR needed?
Currently tests don't access the test data directory in a consistent way. For example, many use os.path.join("tests", "data") which means pytest fails when run from any location apart from the top directory.

Also, fixtures aren't consistently used for data generated inside of test modules.

What does this PR do?

This PR creates a data_path fixture inside of tests/tests/conftest.py that can be re-used by all tests. This ensures pytest can be run from any location successfully.

The PR also makes sure that any data generated inside of tests is wrapped into a fixture.

References

None

How has this PR been tested?

All tests pass locally.

Is this a breaking change?

No

Does this PR require an update to the documentation?

No

Checklist:

• The code has been tested locally
• Tests have been added to cover all new functionality (unit & integration)
• The documentation has been updated to reflect any changes
• The code has been formatted with pre-commit

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.07%. Comparing base (87ca009) to head (830c1d2).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #58   +/-   ##
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  Coverage   84.07%   84.07%           
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  Files          35       35           
  Lines        1331     1331           
=======================================
  Hits         1119     1119           
  Misses        212      212           

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[K-Meech]

Ok - all fixed now! Data has been moved to the data folder, + some fixtures changed to parametrize, + I noticed I'd missed the test_pandas/test_pandas_misc file so I updated that to match the rest. @willGraham01 - could you maybe take a quick look, then merge if you're happy with it? Thanks!