@@ -3,7 +3,10 @@
 import json
 from pathlib import Path
 
-from git import _backend
+import pytest
+
+from git import Repo, _backend
+from test.lib import GIT_REPO, TestBase
 
 
 def pytest_addoption(parser):
@@ -30,3 +33,38 @@ def pytest_terminal_summary(terminalreporter, exitstatus, config):
         with open(path, "w", encoding="utf-8") as stream:
             json.dump(records, stream, indent=2)
             stream.write("\n")
+
+
+@pytest.fixture(scope="session")
+def dependency_repo_factory(tmp_path_factory):
+    """Prepare each immutable historical clone source only when a test needs it."""
+    root = tmp_path_factory.mktemp("dependency-repos")
+    paths = {}
+
+    def get(name):
+        if name not in paths:
+            revision = {
+                "gitdb": "2da3232f9d58e7761e384ac6d32f7b1ed77a74a2",
+                "smmap": "8ce61ad5cc4016bffaf25080bc0d69b3acbe8555",
+            }[name]
+            path = root / name
+            with Repo(GIT_REPO) as source, source.clone(path, shared=True, no_checkout=True) as repo:
+                repo.create_head("master", repo.commit(revision), force=True).checkout()
+                if name == "smmap":
+                    repo.create_tag("v0.8.1", ref="master~10", message="Test fixture tag", force=True)
+                repo.git.gc()
+            paths[name] = str(path)
+        return paths[name]
+
+    return get
+
+
+@pytest.fixture(scope="class", autouse=True)
+def historical_dependency_sources(request):
+    if request.cls is not None and issubclass(request.cls, TestBase):
+        factory = request.getfixturevalue("dependency_repo_factory")
+        request.cls._dependency_repo_factory = staticmethod(factory)
+        yield
+        del request.cls._dependency_repo_factory
+    else:
+        yield
@@ -395,13 +395,13 @@ def _small_repo_url(self):
         """:return: A path to a small, clonable repository"""
         from git.cmd import Git
 
-        return Git.polish_url(self._dependency_repo_dirs["smmap"])
+        return Git.polish_url(self._dependency_repo_factory("smmap"))
 
     def _gitdb_repo_url(self):
         """:return: A local gitdb repository reconstructed from merged history"""
         from git.cmd import Git
 
-        return Git.polish_url(self._dependency_repo_dirs["gitdb"])
+        return Git.polish_url(self._dependency_repo_factory("gitdb"))
 
     @classmethod
     def setUpClass(cls):
@@ -413,26 +413,11 @@ def setUpClass(cls):
 
         gc.collect()
         cls.rorepo = Repo(GIT_REPO)
-        cls._dependency_repo_root = tempfile.mkdtemp(prefix="gitpython-dependency-repos-")
-        cls._dependency_repo_dirs = {}
-        for name, rev in {
-            "gitdb": "2da3232f9d58e7761e384ac6d32f7b1ed77a74a2",
-            "smmap": "8ce61ad5cc4016bffaf25080bc0d69b3acbe8555",
-        }.items():
-            path = osp.join(cls._dependency_repo_root, name)
-            repo = cls.rorepo.clone(path, shared=True, no_checkout=True)
-            repo.create_head("master", repo.commit(rev), force=True).checkout()
-            if name == "smmap":
-                repo.create_tag("v0.8.1", ref="master~10", message="Test fixture tag", force=True)
-            repo.git.gc()
-            repo.close()
-            cls._dependency_repo_dirs[name] = path
 
     @classmethod
     def tearDownClass(cls):
         cls.rorepo.git.clear_cache()
         cls.rorepo.git = None
-        rmtree(cls._dependency_repo_root)
 
     def _make_file(self, rela_path, data, repo=None):
         """