tests/thread: Add tests that mutate shared objects.

Tests concurrent mutating access to: list, dict, set, bytearray.

tests/thread/mutate_bytearray.py

@@ -0,0 +1,44 @@
+# test concurrent mutating access to a shared bytearray object
+#
+# MIT license; Copyright (c) 2016 Damien P. George on behalf of Pycom Ltd
+
+import _thread
+
+# the shared bytearray
+ba = bytearray()
+
+# main thread function
+def th(n, lo, hi):
+    for repeat in range(n):
+        for i in range(lo, hi):
+            l = len(ba)
+            ba.append(i)
+            assert len(ba) >= l + 1
+
+            l = len(ba)
+            ba.extend(bytearray([i]))
+            assert len(ba) >= l + 1
+
+    with lock:
+        global n_finished
+        n_finished += 1
+
+lock = _thread.allocate_lock()
+n_thread = 4
+n_finished = 0
+
+# spawn threads
+for i in range(n_thread):
+    _thread.start_new_thread(th, (40, i * 256 // n_thread, (i + 1) * 256 // n_thread))
+
+# busy wait for threads to finish
+while n_finished < n_thread:
+    pass
+
+# check bytearray has correct contents
+print(len(ba))
+count = [0 for _ in range(256)]
+for b in ba:
+    count[b] += 1
+print(count)
+