diff --git a/tests/unit/rate_limiter_window_invariants_test.py b/tests/unit/rate_limiter_window_invariants_test.py
new file mode 100644
index 0000000..a059361
--- /dev/null
+++ b/tests/unit/rate_limiter_window_invariants_test.py
@@ -0,0 +1,18 @@
+import pytest
+import time
+
+def test_sliding_window_burst_clamping():
+    max_burst = 20
+    window_seconds = 60
+    incoming_requests = 25
+    admitted = min(incoming_requests, max_burst)
+
+    assert admitted == 20
+    assert incoming_requests - admitted == 5
+
+def test_cooldown_expiry_invariants():
+    cooldown_seconds = 10
+    start_time = 100
+    current_time = 112
+
+    assert (current_time - start_time) >= cooldown_seconds