Restructure tests

[khoroshevskyi]

As good praises we shouldn't use actual databases for testing.
Consider to use: another test class instead of bedbaseconfig to write data to txt file or any similar file. Also consider using @runtime_checkable for that

[nsheff]

I just made it so that the tests will skip automatically if the database isn't running; so, we're set up to easily accommodate tests that don't require database connection now.