diff --git a/tests/test.py b/tests/test.py
index a9d7a20..4b8e2a9 100644
--- a/tests/test.py
+++ b/tests/test.py
@@ -2,15 +2,22 @@
 
 from tempfile import TemporaryDirectory
 import os
+import sys
 import subprocess
 from pathlib import Path
 import shutil
 import unittest
+from typing import List
 
 
 TEST_ROOT = Path(__file__).resolve().parent
 
 
+def run(cmd: List[str], **kwargs) -> subprocess.CompletedProcess:
+    print("$ " + " ".join(cmd))
+    return subprocess.run(cmd, **kwargs)
+
+
 class IntegrationTest(unittest.TestCase):
     def setUp(self) -> None:
         self.env = os.environ.copy()
@@ -24,12 +31,32 @@ class IntegrationTest(unittest.TestCase):
             f.write(f"use nix")
 
     def test_direnv(self) -> None:
-        subprocess.run(
-            ["direnv", "allow"], cwd=str(self.testenv), env=self.env, check=True
+        run(["direnv", "allow"], cwd=str(self.testenv), env=self.env, check=True)
+
+        run(["nix-collect-garbage"], check=True)
+
+        out1 = run(
+            ["direnv", "exec", str(self.testenv), "hello"],
+            env=self.env,
+            stderr=subprocess.PIPE,
+            text=True,
         )
-        subprocess.run(
-            ["direnv", "exec", str(self.testenv), "hello"], env=self.env, check=True
+        sys.stderr.write(out1.stderr)
+        self.assertIn("renewed cache and derivation link", out1.stderr)
+        self.assertEqual(out1.returncode, 0)
+
+        run(["nix-collect-garbage"], check=True)
+        run(["sh", "-c", "realpath /nix/var/nix/gcroots/per-user/$USER/*"], check=True)
+
+        out2 = run(
+            ["direnv", "exec", str(self.testenv), "hello"],
+            env=self.env,
+            stderr=subprocess.PIPE,
+            text=True,
         )
+        sys.stderr.write(out2.stderr)
+        self.assertIn("using cached derivation", out2.stderr)
+        self.assertEqual(out2.returncode, 0)
 
     def tearDown(self) -> None:
         self.dir.cleanup()