Create unit tests for Fullness

[patrickanguyen]

Description

After creating the basic implementation of the Fullness class, you need to create unit tests to prove that your implementation functions, and that we can make sure it can continue to work.

Create tests in test/test_desktop_fullness to test all of the public functions in Fullness. Use MockDistance to simulate distance measurements.

Depends on #10

Requirements

• Create at least 5 tests that test getFullness()
• Create at least 5 tests that test isValidFullness()
• Be sure to test every edge case