Implement new Javascript test case sync mechanism (#328) #225

All 1 281 tests pass, 15 skipped in 1m 21s

      4 files ±0       4 suites ±0 1m 21s ⏱️ -1s
1 296 tests - 2 1 281 ✔️ - 2 15 💤 ±0 0 ❌ ±0
1 302 runs - 2 1 287 ✔️ - 2 15 💤 ±0 0 ❌ ±0

Results for commit 6ac4a87. ± Comparison against earlier commit cf743db.