Only one assertion per test

[frankwis]

In general there should be only one assertion per test method to avoid hiding further assertion failures after the first failing assertion which effectively may hide the real severity of the problem.

See http://blog.jayfields.com/2007/06/testing-one-assertion-per-test.html

Also reoccurring words in several test methods are a sign that the tests should be grouped together, i.e. with @Enclosed. Since that feature is still experimental let's discuss what we want to do.

(See comments for PR #14 )