Implemented unittest import check

tests/integration/test_unittest_imports.py

@@ -0,0 +1,36 @@
+# File: tests/integration/test_unittest_imports.py
+
+import os
+import unittest
+
+class TestUnittestImports(unittest.TestCase):
+    TEST_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))
+
+    def test_all_test_files_import_unittest(self):
+        missing = []
+
+        for root, dirs, files in os.walk(self.TEST_ROOT):
+            for filename in files:
+                if not filename.endswith('.py'):
+                    continue
+                # only consider test files named like "test_*.py"
+                if not filename.startswith('test_'):
+                    continue
+
+                filepath = os.path.join(root, filename)
+                with open(filepath, encoding='utf-8') as f:
+                    content = f.read()
+
+                # check for either import form
+                if 'import unittest' not in content and 'from unittest import' not in content:
+                    rel_path = os.path.relpath(filepath, os.getcwd())
+                    missing.append(rel_path)
+
+        if missing:
+            self.fail(
+                "The following test files do not import unittest:\n" +
+                "\n".join(f"- {path}" for path in missing)
+            )
+
+if __name__ == '__main__':
+    unittest.main()