1 files changed, 16 insertions, 0 deletions
diff --git a/frontend/src/test-setup.ts b/frontend/src/test-setup.ts
index cdd6071..10f9568 100644
--- a/frontend/src/test-setup.ts
+++ b/frontend/src/test-setup.ts
@@ -1,4 +1,20 @@
 
+// layerchart reads window.matchMedia (settings context, dark-mode aware
+// styling) in jsdom where no backend exists. Narrow shim for media queries
+// used by chart settings only.
+if (typeof window !== 'undefined' && !window.matchMedia) {
+  window.matchMedia = (query: string) => ({
+    matches: false,
+    media: query,
+    onchange: null,
+    addEventListener: () => {},
+    removeEventListener: () => {},
+    addListener: () => {},
+    removeListener: () => {},
+    dispatchEvent: () => false
+  });
+}
+
 // jsdom does not implement Range.getClientRects, which CodeMirror's
 // measurement layer calls for drawing decorations (diagnostics markers).
 // Without it the suite emits an unhandled