runTests()

This function runs a few examples to test the matrix inversion and caching.

• There are 5 test cases, 3 are expected to work, 2 are expected to fail.
• An inner function handles the common stuff.
• A successful test returns the associated identity matrix.
• A test failure reports the error and continues onto the next test.

Note: I have had to round the identity matrix values (8 significant digits)