--- a/test/conftest.py
+++ b/test/conftest.py
@@ -0,0 +1,28 @@
+import os
+import shutil
+import tempfile
+
+import pytest
+
+import pyproj
+
+
+@pytest.fixture(scope="session")
+def aoi_data_directory():
+    """
+    This is to ensure that the ntv2_0.gsb file is actually
+    missing for the AOI tests.
+    """
+    data_dir = pyproj.datadir.get_data_dir()
+    with tempfile.TemporaryDirectory() as tmpdir:
+        tmp_data_dir = os.path.join(tmpdir, "proj")
+        shutil.copytree(data_dir, tmp_data_dir)
+        try:
+            os.remove(os.path.join(str(tmp_data_dir), "ntv2_0.gsb"))
+        except OSError:
+            pass
+        try:
+            pyproj.datadir.set_data_dir(str(tmp_data_dir))
+            yield
+        finally:
+            pyproj.datadir.set_data_dir(data_dir)