Updata Tests for file import functions - importing csv files

[warren-davies4]

The tests for the file import functions scan the current directory and pass if they find nothing, because the test assumes there are no csvs or xlsx files in the project folder.

However the tests failed because sometimes packages contain csv files, and if you have one installed, the function will find it in your vanv folder.

This will be updated so that the test only scans the tests/ folder.

However this only tests when it successfully doesn't find a file. We should also add two more tests:

• test that it correctly finds a csv file
• test that it correctly finds more than one csvs by looking in subdirectories also