Improve unit test coverage per bug/934566.
Improve unit test coverage per bug/934566.

bug/934566 identified an error which should have been caught by
more complete unit test coverage. This review extends unit test
coverage and is one of a series I will be sending.

Change-Id: I76b966fc2bf18940d0dc0475f3776f8a3148a78d

n0ano/ganttclient