Honor configurable cache size with LRU eviction

tests/test_core.py

@@ -64,6 +64,26 @@ class CoreTests(unittest.TestCase):
         source.write_bytes(b"changed")
         self.assertFalse(manager.cache_valid(relative))
 
+    def test_smaller_cache_limit_evicts_oldest_content(self):
+        m = self.module
+        manager = m.Manager()
+        relative = "movies/Resize/Resize.mkv"
+        source = self.root / "source" / relative
+        source.parent.mkdir(parents=True, exist_ok=True)
+        source.write_bytes(b"original")
+        output, manifest = manager.cache_paths(relative)
+        output.write_bytes(b"cached rendition")
+        manifest.write_text(json.dumps({"relative": relative, "source_fingerprint": m.fingerprint(source)}))
+        manager.ensure_link(relative, m.cache_target(relative))
+        old_limit = m.CACHE_MAX_BYTES
+        try:
+            m.CACHE_MAX_BYTES = 1
+            manager.enforce_cache_limit()
+        finally:
+            m.CACHE_MAX_BYTES = old_limit
+        self.assertFalse(output.exists())
+        self.assertEqual(os.readlink(self.root / "view" / relative), m.source_target(relative))
+
 
 if __name__ == "__main__":
     unittest.main()