Reuse DiffPerformanceTest support code to validate algorithms

Each algorithm should produce a particular number of results
given one of the standard inputs used during the performance
tests.  To help ensure those tests are accurate, assert that
the edit list length is correct.

Change-Id: I292f8fde0cec6a60a75ce09e70814a00ca47cb99
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
3 files changed