diff --git a/src/testdir/thread_util.py b/src/testdir/thread_util.py
new file mode 100644
index 0000000..e82f23c
--- /dev/null
+++ b/src/testdir/thread_util.py
@@ -0,0 +1,90 @@
+import platform
+
+if platform.system() == 'Darwin':
+    from ctypes import (
+        CDLL,
+        POINTER,
+        Structure,
+        byref,
+        c_int,
+        c_uint,
+        c_uint32,
+        c_void_p,
+        sizeof
+    )
+    from ctypes.util import find_library
+
+    class ThreadTimeConstraintPolicy(Structure):
+        _fields_ = [
+            ("period", c_uint32),
+            ("computation", c_uint32),
+            ("constraint", c_uint32),
+            ("preemptible", c_uint)
+        ]
+
+    _libc = CDLL(find_library('c'))
+
+    THREAD_TIME_CONSTRAINT_POLICY = c_uint(2)
+
+    THREAD_TIME_CONSTRAINT_POLICY_COUNT = c_uint(
+        int(sizeof(ThreadTimeConstraintPolicy) / sizeof(c_int)))
+
+    _libc.pthread_self.restype = c_void_p
+
+    _libc.pthread_mach_thread_np.restype = c_uint
+    _libc.pthread_mach_thread_np.argtypes = [c_void_p]
+
+    _libc.thread_policy_get.restype = c_int
+    _libc.thread_policy_get.argtypes = [
+        c_uint,
+        c_uint,
+        c_void_p,
+        POINTER(c_uint),
+        POINTER(c_uint)
+    ]
+
+    _libc.thread_policy_set.restype = c_int
+    _libc.thread_policy_set.argtypes = [
+        c_uint,
+        c_uint,
+        c_void_p,
+        c_uint
+    ]
+
+    def _mach_thread_self():
+        return _libc.pthread_mach_thread_np(_libc.pthread_self())
+
+    def _get_time_constraint_policy(default=False):
+        thread = _mach_thread_self()
+        policy_info = ThreadTimeConstraintPolicy()
+        policy_infoCnt = THREAD_TIME_CONSTRAINT_POLICY_COUNT
+        get_default = c_uint(default)
+
+        kret = _libc.thread_policy_get(
+            thread,
+            THREAD_TIME_CONSTRAINT_POLICY,
+            byref(policy_info),
+            byref(policy_infoCnt),
+            byref(get_default))
+        if kret != 0:
+            return None
+        return policy_info
+
+    def _set_time_constraint_policy(policy_info):
+        thread = _mach_thread_self()
+        policy_infoCnt = THREAD_TIME_CONSTRAINT_POLICY_COUNT
+
+        kret = _libc.thread_policy_set(
+            thread,
+            THREAD_TIME_CONSTRAINT_POLICY,
+            byref(policy_info),
+            policy_infoCnt)
+        if kret != 0:
+            raise OSError(kret)
+
+    def set_high_priority():
+        policy_info = _get_time_constraint_policy(default=True)
+        if not policy_info:
+            return
+        policy_info.preemptible = c_uint(False)
+        _set_time_constraint_policy(policy_info)