1 files changed, 57 insertions, 1 deletions
diff --git a/tests/builder/cache.test.py b/tests/builder/cache.test.py
index 700a8e4..045e8e9 100644
--- a/tests/builder/cache.test.py
+++ b/tests/builder/cache.test.py
@@ -1,8 +1,33 @@
-"""Tests for the per-instance lazy compile cache."""
+"""Tests for the per-instance lazy compile cache — semantics and cold/warm ratio."""
+
+import time
 
 from edify import Pattern, RegexBuilder
 
 
+def _hex_number_builder():
+    return (
+        RegexBuilder()
+        .start_of_input()
+        .assert_ahead()
+        .any_of("0x", "0o", "0b")
+        .end()
+        .capture()
+        .any_of("0x", "0o", "0b")
+        .end()
+        .between(1, 16)
+        .any_of_chars("0123456789abcdefABCDEF")
+        .end_of_input()
+    )
+
+
+def _measure_call_wall_clock(action, iterations):
+    start = time.perf_counter()
+    for _ in range(iterations):
+        action()
+    return time.perf_counter() - start
+
+
 def test_two_no_kwargs_to_regex_calls_return_the_same_instance():
     builder = RegexBuilder().one_or_more().digit()
     first = builder.to_regex()
@@ -61,3 +86,34 @@ def test_chain_step_yields_a_fresh_cache_slot():
 def test_pattern_also_caches_across_repeat_to_regex_calls():
     pattern = Pattern().string("hi")
     assert pattern.to_regex() is pattern.to_regex()
+
+
+def test_warm_to_regex_is_at_least_ten_times_cheaper_than_cold_to_regex():
+    warm_iterations = 200
+    cold_iterations = 200
+
+    cold_total = 0.0
+    for _ in range(cold_iterations):
+        builder = _hex_number_builder()
+        cold_start = time.perf_counter()
+        builder.to_regex()
+        cold_total += time.perf_counter() - cold_start
+
+    warm_builder = _hex_number_builder()
+    warm_builder.to_regex()
+    warm_total = _measure_call_wall_clock(warm_builder.to_regex, warm_iterations)
+
+    average_cold = cold_total / cold_iterations
+    average_warm = warm_total / warm_iterations
+
+    assert average_warm * 10 < average_cold, (
+        f"cache ratio too weak: warm={average_warm * 1e6:.2f}µs, "
+        f"cold={average_cold * 1e6:.2f}µs — warm should be < cold / 10."
+    )
+
+
+def test_repeat_to_regex_returns_the_same_regex_instance():
+    warm_builder = _hex_number_builder()
+    first = warm_builder.to_regex()
+    second = warm_builder.to_regex()
+    assert first is second