Refactor `count_occurrences` #1662

All 766 tests pass, 20 skipped in 1m 38s

      1 files ±0     80 suites ±0 1m 38s ⏱️ +15s
  786 tests ±0   766 ✔️ ±0   20 💤 ±0 0 ❌ ±0
1 668 runs ±0 1 036 ✔️ ±0 632 💤 ±0 0 ❌ ±0

Results for commit 8e70abf. ± Comparison against earlier commit 961ffe9.