tests: Improve ClockObject tests

Closes #898

tests/putil/test_clockobject.py

@@ -1,4 +1,5 @@
 import time
+from pytest import approx
 
 
 def test_clock_get_frame_time(clockobj):
@@ -15,8 +16,14 @@ def test_clock_jump_frame_time(clockobj):
 
 def test_clock_get_real_time(clockobj):
     current_time = clockobj.get_real_time()
-    time.sleep(0.2)
-    assert current_time != clockobj.get_real_time()
+    time.sleep(0.4)
+    assert clockobj.get_real_time() - current_time == approx(0.4, 0.1)
+
+
+def test_clock_get_long_time(clockobj):
+    current_time = clockobj.get_long_time()
+    time.sleep(0.4)
+    assert clockobj.get_long_time() - current_time == approx(0.4, 0.1)
 
 
 def test_clock_get_dt(clockobj):