diff --git a/pyproject.toml b/pyproject.toml
index f36091db..73002860 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -66,6 +66,7 @@ test = [
   "parameterized==0.9",
   "pytest>=7",
   "pytest-cov>=6.2.1",
+  "pytest-xdist>=3",
   "types-beautifulsoup4==4.12.0.20250516",
   "types-requests==2.33.0.20260518",
   "types-tqdm==4.68.0.20260608",
@@ -85,7 +86,7 @@ envs.hatch-test.overrides.matrix.python.features = [
 ]
 # pyproject.toml is the single source of truth for the environments CI tests:
 # the workflow reads this matrix via `hatch env show --json`.
-envs.hatch-test.default-args = [ "tests" ]
+envs.hatch-test.default-args = [ "-n", "auto", "tests" ]
 envs.hatch-test.dependency-groups = [ "test" ]
 
 [tool.ruff]
diff --git a/tests/test_virus.py b/tests/test_virus.py
index 12798ac1..673e0dbe 100644
--- a/tests/test_virus.py
+++ b/tests/test_virus.py
@@ -261,24 +261,11 @@ class TestVirus(unittest.TestCase, metaclass=from_json(virus_dict, virus)):
     See module docstring for detailed parameter coverage analysis.
     """
 
-    @classmethod
-    def setUpClass(cls):
-        """Set up test fixtures that are shared across all tests."""
-        cls.test_output_dir = "test_virus_output"
-
-    @classmethod
-    def tearDownClass(cls):
-        """Clean up after all tests have run."""
-        # Clean up test output directory if it exists
-        if os.path.exists(cls.test_output_dir):
-            shutil.rmtree(cls.test_output_dir)
-
     def setUp(self):
         """Set up before each test method."""
-        # Create a fresh test output directory
-        if os.path.exists(self.test_output_dir):
-            shutil.rmtree(self.test_output_dir)
-        os.makedirs(self.test_output_dir, exist_ok=True)
+        # Create a unique per-test output directory so tests can run in parallel
+        # (pytest-xdist) without racing on a shared, fixed directory.
+        self.test_output_dir = tempfile.mkdtemp(prefix="test_virus_")
 
     def tearDown(self):
         """Clean up after each test method."""