adding first key-value pair.
beta == beta
checking for failure to insert.
adding second key-value pair.
delta == delta
adding four more key-value pairs.
c["unos"] = eins
c["dos"] = zwei
c["tres"] = drei
c["quatro"] = vier
testing lookup invariants.
Testing iterator interface.
beta, zwei, delta, vier, drei, eins, 
End of tests.
