test: add tests for RateLimiter and AsyncRateLimiter

tests/test_rate_limiter.py

@@ -0,0 +1,28 @@
+"""Tests for utils.rate_limiter."""
+import time
+import pytest
+from utils.rate_limiter import RateLimiter
+
+
+def test_allows_burst():
+    limiter = RateLimiter(calls_per_second=100, burst=5)
+    start = time.monotonic()
+    for _ in range(5):
+        limiter.acquire()
+    elapsed = time.monotonic() - start
+    assert elapsed < 0.1  # burst should be near-instant
+
+
+def test_rate_limits():
+    limiter = RateLimiter(calls_per_second=20)
+    start = time.monotonic()
+    for _ in range(3):
+        limiter.acquire()
+    elapsed = time.monotonic() - start
+    # 3 calls at 20/s should take ~0.1s
+    assert elapsed >= 0.05
+
+
+def test_callable_interface():
+    limiter = RateLimiter(calls_per_second=100)
+    limiter()  # should not raise