Match the 13-bus redirect to IEEELineCodes.DSS so it compiles on Linux

OpenDSS/13Bus/IEEE13Nodeckt.dss

@@ -43,7 +43,7 @@ New Transformer.XFM1  Phases=3   Windings=2  XHL=2
 
 
 !LINE CODES
-redirect IEEELineCodes.dss
+redirect IEEELineCodes.DSS
 
 // these are local matrix line codes
 // corrected 9-14-2011

OpenDSS/13Bus/IEEE13Nodeckt_com_loadshape.dss

@@ -43,7 +43,7 @@ New Transformer.XFM1  Phases=3   Windings=2  XHL=2
 
 
 !LINE CODES
-redirect IEEELineCodes.dss
+redirect IEEELineCodes.DSS
 
 // these are local matrix line codes
 // corrected 9-14-2011

tests/test_opendss_case_files.py

@@ -0,0 +1,49 @@
+"""The shipped OpenDSS cases must compile on case-sensitive filesystems.
+
+Windows and macOS resolve ``redirect IEEELineCodes.dss`` against a file named
+``IEEELineCodes.DSS``; Linux does not, and OpenDSS then leaves a circuit with
+no line codes. Compare names exactly so the check fails on every platform.
+"""
+
+from __future__ import annotations
+
+import re
+from pathlib import Path
+
+import pytest
+
+OPENDSS_DIR = Path(__file__).resolve().parents[1] / "OpenDSS"
+_FILE_COMMAND = re.compile(r"^\s*(redirect|compile|buscoords)\s+(\S+)", re.IGNORECASE)
+
+
+def _dss_files():
+    return sorted(p for p in OPENDSS_DIR.rglob("*") if p.suffix.lower() == ".dss")
+
+
+def _referenced_files(dss_file: Path):
+    for line in dss_file.read_text(errors="replace").splitlines():
+        match = _FILE_COMMAND.match(line)
+        if match:
+            yield match.group(2).strip("\"'()[]")
+
+
+def _exists_with_exact_case(base: Path, relative: str) -> bool:
+    current = base
+    for part in Path(relative.replace("\\", "/")).parts:
+        if part in (".", ".."):
+            current = current / part
+            continue
+        if not current.is_dir() or part not in {entry.name for entry in current.iterdir()}:
+            return False
+        current = current / part
+    return current.is_file()
+
+
+@pytest.mark.parametrize("dss_file", _dss_files(), ids=lambda p: str(p.relative_to(OPENDSS_DIR)))
+def test_referenced_files_match_case_exactly(dss_file):
+    missing = [
+        target
+        for target in _referenced_files(dss_file)
+        if not _exists_with_exact_case(dss_file.parent, target)
+    ]
+    assert not missing, f"{dss_file.name} references files that do not exist with this exact case: {missing}"