Package-level declarations

wraps a similarity with checks for testing

Abstract class to do basic tests for a similarity. NOTE: This test focuses on the similarity impl, nothing else. The stretch goal is for this test to be so thorough in testing a new Similarity that if this test passes, then all Lucene tests should also pass. Ie, if there is some bug in a given Similarity that this test fails to catch then this test needs to be improved!

Similarity implementation that randomizes Similarity implementations per-field.