Adding Unit Tests for Maybe

[FRosner]

Problem

There are no unit tests for the public functions of the Maybe module. This makes it impossible to apply refactoring to the existing code without knowing whether this will break the expected behaviour.

Also, unit tests are good examples on how to use an API. All public functions should have unit tests.

Solution

Add unit tests.

[process-bot]

Thanks for the pull request! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[process-bot]

Thanks for the pull request! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[rtfeldman]

Thanks @FRosner!

[rtfeldman]

Thanks @FRosner!