# crosshair check /tmp/ch_demo.py
add: post condition was violated
  Counterexample: add(0, 0) -> 1 (expected 0)
Found 1 error in 1 function.

# crosshair cover /tmp/ch_demo.py
test_deduplicate_1: deduplicate([]) == []
test_deduplicate_2: deduplicate([1]) == [1]