1 files changed, 31 insertions, 0 deletions
diff --git a/tests/test_helper.py b/tests/test_helper.py
new file mode 100644
index 0000000..d37c03a
--- /dev/null
+++ b/tests/test_helper.py
@@ -0,0 +1,31 @@
+import unittest
+
+from sqlglot.helper import tsort
+
+
+class TestHelper(unittest.TestCase):
+    def test_tsort(self):
+        self.assertEqual(tsort({"a": []}), ["a"])
+        self.assertEqual(tsort({"a": ["b", "b"]}), ["b", "a"])
+        self.assertEqual(tsort({"a": ["b"]}), ["b", "a"])
+        self.assertEqual(tsort({"a": ["c"], "b": [], "c": []}), ["c", "a", "b"])
+        self.assertEqual(
+            tsort(
+                {
+                    "a": ["b", "c"],
+                    "b": ["c"],
+                    "c": [],
+                    "d": ["a"],
+                }
+            ),
+            ["c", "b", "a", "d"],
+        )
+
+        with self.assertRaises(ValueError):
+            tsort(
+                {
+                    "a": ["b", "c"],
+                    "b": ["a"],
+                    "c": [],
+                }
+            )