diff --git a/tests/test_fix_ascendancy_positions.py b/tests/test_fix_ascendancy_positions.py
new file mode 100644
index 00000000..690dc8df
--- /dev/null
+++ b/tests/test_fix_ascendancy_positions.py
@@ -0,0 +1,29 @@
+import filecmp
+import pathlib
+import shutil
+import tempfile
+
+import fix_ascendancy_positions
+
+
+def test_fix_one() -> None:
+    raw = pathlib.Path("data.json")
+    fixed = pathlib.Path("data_fixed.json")
+    with tempfile.TemporaryDirectory() as td:
+        new = pathlib.Path(td, raw)
+        shutil.copy(raw, td)
+        fix_ascendancy_positions.fix_ascendancy_positions(new)
+        assert filecmp.cmp(new, fixed, shallow=False)
+
+
+def test_fix_all() -> None:
+    raw = pathlib.Path("data.json")
+    fixed = pathlib.Path("data_fixed.json")
+    with tempfile.TemporaryDirectory() as outer, tempfile.TemporaryDirectory(
+        dir=outer
+    ) as inner:
+        root = pathlib.Path(outer)
+        new = pathlib.Path(inner, raw)
+        shutil.copy(raw, inner)
+        fix_ascendancy_positions.main(root)
+        assert filecmp.cmp(new, fixed, shallow=False)