Alter to allow assert invokation... Test output...
idea is to use it from FractionCalculatorTest to test FractionTest
routinely during further development.

Test output ...
$ java -ea FractionTest
FractionTest tests verbose output:
test "Divide by zero: that 1/0 should throw an IllegalArgumentException exception" passes.
test ".equal method: that 1/2 .equals 1/2" passes.
test ".equal method: that 1/2 equals 3/6" passes.
test ".equal method: that -1/2 equals 1/-2" passes.
test ".equal method: that -1/-2 equals 1/2" passes.
test ".equal method: that 4/-8 does not equal 1/2" passes.
test "Multiply: that multiplying 1/2 by 3/5 gives 3/10" passes.
test "Divide: that (2/9) / (3/5) gives 10/27" passes.
test "Add: that 1/2 + 1/4 gives 3/4" passes.
test "Add: that 2/9 + 3/5 gives 37/45" passes.
test "Subtract: that 2/9 - 3/5 gives -17/45" passes.
test "AbsValue: that absValue(-7/9) = 7/9" passes.
test "Negate: that Negate(7/9) = -7/9" passes.
test ".toString(): that (6/5).toString() is equal to "6/5" " passes.
test ".toString(): that (6/1).toString() is equal to "6" " passes.
FractionTest: All tests pass
first assert FractionTest... Test output...
idea is to routinely use FractionTest to test Fraction during development
of this FractionCalculator. The FractionTest output is silent if no
error is found.

So Test output is not altered (-ea enables assertions) ...

$ java -ea FractionCalculatorTest
FractionTestCalculator tests verbose output:
debug call to process with inputString ="quit"