message: Added a test for no merge or dedup
  Added a test for data where merge and deduplication isn't necessary.
diff: @@ -424,4 +424,40 @@ mod tests {
  let all = t1.all_traces();
  assert_eq!(all.len(), 2);
  }
  +
  + #[test]
  + fn merge_needed() {
  + let mut t1 = TraceMap::new();
  + let mut t2 = TraceMap::new();
  +
  + t1.add_trace(Path::new("file.rs"), Trace {
  + line: 2,
  + address: Some(1),
  + length: 0,
  + stats: CoverageStat::Line(5)
  + });
  + t2.add_trace(Path::new("file.rs"), Trace {
  + line: 2,
  + address: Some(1),
  + length: 0,
  + stats: CoverageStat::Line(2)
  + });
  + t1.merge(&t2);
  + assert_eq!(t1.all_traces().len(), 1);
  + assert_eq!(t1.get_trace(1), Some(&Trace {
  + line: 2,
  + address: Some(1),
  + length: 0,
  + stats: CoverageStat::Line(7)
  + }));
  + // Deduplicating should have no effect.
  + t1.dedup();
  + assert_eq!(t1.all_traces().len(), 1);
  + assert_eq!(t1.get_trace(1), Some(&Trace {
  + line: 2,
  + address: Some(1),
  + length: 0,
  + stats: CoverageStat::Line(7)
  + }));
  + }
  }
  