End to End tests and Unit tests

on E2E vs unit: http://googletesting.blogspot.com/2015/04/just-say-no-to-more-end-to-end-tests.html

Pointed out "gold standard" of unit testing in guava, i.e. https://github.com/google/guava/blob/master/guava-tests/test/com/google/common/base/StopwatchTest.java testing https://github.com/google/guava/blob/master/guava/src/com/google/common/base/Stopwatch.java