diff --git a/tests/test_raw_parser.py b/tests/test_raw_parser.py
index 9a42bef..db8d45b 100644
--- a/tests/test_raw_parser.py
+++ b/tests/test_raw_parser.py
@@ -69,6 +69,22 @@ class TestRawFileGetVariable:
         assert len(result) == mock_rawfile.points
 
 
+class TestRawFileResolveIndex:
+    def test_exact_match_returns_index(self, mock_rawfile):
+        assert mock_rawfile.resolve_index("V(out)") == 1
+        assert mock_rawfile.resolve_index("time") == 0
+
+    def test_case_insensitive(self, mock_rawfile):
+        assert mock_rawfile.resolve_index("v(out)") == 1
+
+    def test_partial_does_not_match(self, mock_rawfile):
+        """Unlike get_variable, resolve_index requires an exact name match."""
+        assert mock_rawfile.resolve_index("out") is None
+
+    def test_missing_returns_none(self, mock_rawfile):
+        assert mock_rawfile.resolve_index("V(nonexistent)") is None
+
+
 class TestRawFileRunData:
     def test_get_run_data_slicing(self, mock_rawfile_stepped):
         """Extracting a single run produces correct point count."""