General FizzBuzz in Scala
Map is not guaranteed to impose or preserve any order for its entries.  For example, if I change Factors to …

private final val Factors = Map(3 -&gt; "a", 5 -&gt; "b", 6 -&gt; "c", 7 -&gt; "d", 8 -&gt; "e", 9 -&gt; "f")


… I get:


⁞
89
bcfa
d
92
a
94
b
cae
97
d
fa
b



So, the fact that you get "fizzbuzz" rather than "buzzfizz" is based on luck, not skill.  If you want to guarantee "fizzbuzz", you need a scala.collection.immutable.SortedMap.