tests: Add tests for sys.settrace feature.

tests/misc/sys_settrace_loop.py

@@ -0,0 +1,51 @@
+# test sys.settrace with while and for loops
+
+import sys
+
+try:
+    sys.settrace
+except AttributeError:
+    print("SKIP")
+    raise SystemExit
+
+def print_stacktrace(frame, level=0):
+    print("%2d: %s@%s:%s => %s:%d" % (
+        level, "  ",
+        frame.f_globals['__name__'],
+        frame.f_code.co_name,
+        # reduce full path to some pseudo-relative
+        'misc' + ''.join(frame.f_code.co_filename.split('tests/misc')[-1:]),
+        frame.f_lineno,
+    ))
+
+    if frame.f_back:
+        print_stacktrace(frame.f_back, level + 1)
+
+trace_count = 0
+
+def trace_tick_handler(frame, event, arg):
+    global trace_count
+    print("### trace_handler::main event:", event)
+    trace_count += 1
+    print_stacktrace(frame)
+    return trace_tick_handler
+
+def test_loop():
+    # for loop
+    r = 0
+    for i in range(3):
+        r += i
+    print("test_for_loop", r)
+
+    # while loop
+    r = 0
+    i = 0
+    while i < 3:
+        r += i
+        i += 1
+    print("test_while_loop", i)
+
+sys.settrace(trace_tick_handler)
+test_loop()
+sys.settrace(None)
+print("Total traces executed: ", trace_count)