Make the mock data mutable inside the scope of a test
Make the mock data mutable inside the scope of a test

Also, add a test that demonstrates that

UMM-CSci-3601-S17/digital-display-garden-iteration-3-dorfner,UMM-CSci-3601-S17/digital-display-garden-iteration-3-dorfner,UMM-CSci-3601-S17/digital-display-garden-iteration-3-dorfner,UMM-CSci-3601-S17/digital-display-garden-iteration-4-dorfner-v2,UMM-CSci-3601-S17/digital-display-garden-iteration-4-dorfner-v2,UMM-CSci-3601-S17/digital-display-garden-iteration-3-dorfner,UMM-CSci-3601-S17/digital-display-garden-iteration-4-dorfner-v2,UMM-CSci-3601-S17/digital-display-garden-iteration-4-dorfner-v2,UMM-CSci-3601-S17/digital-display-garden-iteration-4-dorfner-v2