Test: 101
TPP: unconditional -> if (number == 101), the new execution path is a nil -> constant (return "one hundred one")
I did a refactoring which merges the logic of converting number within a counting unit into one method.
Test: 102, and test name is refactored to "one hundred and single digit convert to three words"
TPP: constant -> scala (1 -> number - 100)
all other code changes are refactorings, including merging the if condition (number == 101 || number == 102) and replace constant with the value from map ("one" -> NUMBER_TO_ONE_WORD.get(1))