test: Increase Project Unittest coverage from 50% to 75.9%

[madhavmk]

• Uncomment testcases in test_geo.py
• Add unittests for download_test_data()
• Add end to end run_gnatss() unittest
• Overall increase of project unittest coverage from 50% to 75.9%
• Related to Issue #261

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 75.85%. Comparing base (2f00e30) to head (127375c). Report is 56 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #279 +/- ## =========================================== + Coverage 49.67% 75.85% +26.17% =========================================== Files 16 29 +13 Lines 930 1752 +822 =========================================== + Hits 462 1329 +867 + Misses 468 423 -45 ```

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