Add unit tests

[sean-g-rae]

Thanks for your contribution to Apache Commons! Your help is appreciated!

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[garydgregory]

Hello @sean-g-rae

This PR needs work. You must make sure that when a change is made to a main class, a corresponding test class fails when the main changes are omitted.

For example, if I apply this PR locally and revert the changes to ColorGroup and run ColorGroupTest, the test is green. This obviously is bad and means that a regression is just waiting to happen.

TY!

[garydgregory]

@sean-g-rae ping 🔔

[sean-g-rae]

@sean-g-rae ping 🔔

Thanks for the feedback! To keep the PR focused, I reverted the non-test change.

[garydgregory]

Hello @sean-g-rae

The build is broken

From the description:

Run a successful build using the default Maven goal with mvn; that's mvn on the command line by itself.

[garydgregory]

Closing: I cleaned up a local diff of this PR that doesn't break the build. You are credited in git master.