Match the settings popup to the browser/OS dark mode preference

tests/popup.test.js

@@ -121,6 +121,31 @@ test("saving an unparseable custom URL is rejected with an error, not saved", as
   assert.strictEqual(savedCalls.length, 0, "should not save an invalid URL");
 });
 
+test("marks the status message as an error (for themed error styling) on a rejected save", async () => {
+  const { window } = loadPopupScript();
+  await wait(20);
+
+  const urlPreset = window.document.getElementById("urlPreset");
+  urlPreset.value = "custom";
+  urlPreset.dispatchEvent(new window.Event("change"));
+  window.document.getElementById("customUrl").value = "   ";
+
+  window.document.getElementById("saveBtn").click();
+  await wait(20);
+
+  assert.strictEqual(window.document.getElementById("status").classList.contains("error"), true);
+});
+
+test("does not mark the status message as an error on a successful save", async () => {
+  const { window } = loadPopupScript();
+  await wait(20);
+
+  window.document.getElementById("saveBtn").click();
+  await wait(20);
+
+  assert.strictEqual(window.document.getElementById("status").classList.contains("error"), false);
+});
+
 test("unchecking a toggle and saving persists it as false", async () => {
   const { window, savedCalls } = loadPopupScript();
   await wait(20);