Test operator== for game

[richelbilderbeek]

Is your feature request related to a problem? Please describe.

Currently, the operator== for game is untested.

Describe the solution you'd like

Write multiple tests to check this operator:

• Two default-constructed games should be the same
• Two default-constructed games, after a change to one game, should result in two different games

These are multiple tests, at least one per member variable.

Describe alternatives you've considered

None.

Additional context

None.