diff --git a/django/test/runner.py b/django/test/runner.py
index c11681fde8..b63ca6adb8 100644
--- a/django/test/runner.py
+++ b/django/test/runner.py
@@ -574,28 +574,7 @@ class DiscoverRunner:
             if not os.path.exists(label_as_path):
                 tests = self.test_loader.loadTestsFromName(label)
             elif os.path.isdir(label_as_path) and not self.top_level:
-                # Try to be a bit smarter than unittest about finding the
-                # default top-level for a given directory path, to avoid
-                # breaking relative imports. (Unittest's default is to set
-                # top-level equal to the path, which means relative imports
-                # will result in "Attempted relative import in non-package.").
-
-                # We'd be happy to skip this and require dotted module paths
-                # (which don't cause this problem) instead of file paths (which
-                # do), but in the case of a directory in the cwd, which would
-                # be equally valid if considered as a top-level module or as a
-                # directory path, unittest unfortunately prefers the latter.
-
-                top_level = label_as_path
-                while True:
-                    init_py = os.path.join(top_level, '__init__.py')
-                    if not os.path.exists(init_py):
-                        break
-                    try_next = os.path.dirname(top_level)
-                    if try_next == top_level:
-                        # __init__.py all the way down? give up.
-                        break
-                    top_level = try_next
+                top_level = find_top_level(label_as_path)
                 kwargs['top_level_dir'] = top_level
 
             if not (tests and tests.countTestCases()) and is_discoverable(label):
@@ -764,6 +743,30 @@ def is_discoverable(label):
     return os.path.isdir(os.path.abspath(label))
 
 
+def find_top_level(top_level):
+    # Try to be a bit smarter than unittest about finding the default top-level
+    # for a given directory path, to avoid breaking relative imports.
+    # (Unittest's default is to set top-level equal to the path, which means
+    # relative imports will result in "Attempted relative import in
+    # non-package.").
+
+    # We'd be happy to skip this and require dotted module paths (which don't
+    # cause this problem) instead of file paths (which do), but in the case of
+    # a directory in the cwd, which would be equally valid if considered as a
+    # top-level module or as a directory path, unittest unfortunately prefers
+    # the latter.
+    while True:
+        init_py = os.path.join(top_level, '__init__.py')
+        if not os.path.exists(init_py):
+            break
+        try_next = os.path.dirname(top_level)
+        if try_next == top_level:
+            # __init__.py all the way down? give up.
+            break
+        top_level = try_next
+    return top_level
+
+
 def reorder_tests(tests, classes, reverse=False):
     """
     Reorder an iterable of tests by test type, removing any duplicates.