Update test_optimizer_config.py (#814)

Add simple tests for rewarmup schedule

tests/test_optimizer_config.py

@@ -172,6 +172,7 @@ def test_rewarmup_schedule():
     assert np.isclose(sched_fn(100), 1e-2)  # Warmup reaches max LR
 
     # First decay phase
+    assert np.isclose(sched_fn(300), 0.6e-2)  # Mid of first decay
     assert np.isclose(sched_fn(500), 0.2e-2)  # End of first decay
 
     # Rewarmup at start of second cycle
@@ -184,4 +185,5 @@ def test_rewarmup_schedule():
     assert sched_fn(rewarmup_end + 1) < sched_fn(rewarmup_end)
 
     # Final decay phase
+    assert sched_fn(999 - 1) > sched_fn(999)
     assert np.isclose(sched_fn(999), 0.2e-2, atol=1e-4)  # End of second decay