diff --git a/.gitignore b/.gitignore
index 49e14ccc8d..5bb0f64707 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,3 +10,4 @@ venv*/
 .python-version
 build/
 dist/
+.idea/
diff --git a/requirements.txt b/requirements.txt
index 0d8ba2eff0..48360c8206 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -28,3 +28,4 @@ trio-typing==0.10.0
 trustme==1.1.0; python_version < '3.9'
 trustme==1.2.0; python_version >= '3.9'
 uvicorn==0.32.1
+blockbuster==1.5.10
diff --git a/tests/conftest.py b/tests/conftest.py
index 858bca1397..f50edc4db4 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -7,6 +7,7 @@
 
 import pytest
 import trustme
+from blockbuster import blockbuster_ctx
 from cryptography.hazmat.backends import default_backend
 from cryptography.hazmat.primitives.serialization import (
     BestAvailableEncryption,
@@ -31,6 +32,13 @@
 }
 
 
+@pytest.fixture(autouse=True)
+def blockbuster():
+    with blockbuster_ctx() as bb:
+        bb.functions["os.stat"].can_block_in("/mimetypes.py", "init")
+        yield bb
+
+
 @pytest.fixture(scope="function", autouse=True)
 def clean_environ():
     """Keeps os.environ clean for every test without having to mock os.environ"""
diff --git a/tests/models/test_whatwg.py b/tests/models/test_whatwg.py
index 14af682586..8f3fa2b0a0 100644
--- a/tests/models/test_whatwg.py
+++ b/tests/models/test_whatwg.py
@@ -3,6 +3,7 @@
 # https://url.spec.whatwg.org/
 
 import json
+from pathlib import Path
 
 import pytest
 
@@ -10,7 +11,8 @@
 
 # URL test cases from...
 # https://github.com/web-platform-tests/wpt/blob/master/url/resources/urltestdata.json
-with open("tests/models/whatwg.json", "r", encoding="utf-8") as input:
+whatwg_path = Path(__file__).parent.parent / "models" / "whatwg.json"
+with whatwg_path.open("r", encoding="utf-8") as input:
     test_cases = json.load(input)
     test_cases = [
         item