highlight issue: msprime produces different trees on macos (same seed)

Author: lkirk

python/tests/test_python_c.py

@@ -2052,9 +2052,9 @@ def norm_func(X, n, nA, nB):
         )
         import platform
 
-        # only run if we're not running on macos
-        if platform.system() in {"Linux", "Windows"}:
-            assert (ts_multi.get_num_sites(), ts_multi.get_num_sites()) == (56, 56)
+        if platform.system() == "Darwin":
+            assert a.shape == (54, 54, 1)  # ts has 54 sites on macos?
+        else:
             assert a.shape == (56, 56, 1)  # ts has 56 sites
         a = ts_multi.two_locus_count_stat(
             ss_sizes, ss, stat_func, norm_func, 1, True, None, None, None, None, "branch"