Add more tests

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 71.72%. Comparing base (044f411) to head (51cca07). Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
cmd/yopass-server/main.go	83.33%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2512 +/- ## ========================================== + Coverage 69.65% 71.72% +2.06% ========================================== Files 8 8 Lines 669 672 +3 ========================================== + Hits 466 482 +16 + Misses 172 158 -14 - Partials 31 32 +1 ```

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