@@ -4,9 +4,11 @@ import { test, vi } from "vitest";
 
 import { bootDebugPage, fire, settle } from "./debug-page-harness.js";
 
-/* The Database panel feature is the failure fixture: it is the only module the
-   bootstrap loads on demand here, and its import must reject for the degraded
-   callout to appear. No other scenario in this file ships a panel marker. */
+/**
+ * The Database panel feature is the failure fixture: it is the only module the
+ * bootstrap loads on demand here, and its import must reject for the degraded
+ * callout to appear. No other scenario in this file ships a panel marker.
+ */
 vi.doMock("../src/panels/db.js", () => {
   throw new Error("Chunk load failed.");
 });
 
@@ -451,8 +451,10 @@ test("a field that cannot place a caret is only refocused", async () => {
   const page = await bootDebugPage({
     body: '<input name="Debug[url]" value="/site/index">',
     prepare(documentValue) {
-      /* Older engines expose no selection API on some input types; the source
-         must still hand the field back its focus. */
+      /**
+       * Older engines expose no selection API on some input types; the source
+       * must still hand the field back its focus.
+       */
       documentValue.querySelector("input").setSelectionRange = undefined;
     },
     sessionData: {
 
@@ -215,8 +215,10 @@ export async function bootDebugPage(options) {
     settings.prepare(documentValue);
   }
 
-  /* jsdom's EventTarget methods reject an inheriting receiver, so the facade
-     forwards them to the window they were taken from. */
+  /**
+   * jsdom's EventTarget methods reject an inheriting receiver, so the facade
+   * forwards them to the window they were taken from.
+   */
   ["addEventListener", "dispatchEvent", "removeEventListener"].forEach(
     function (name) {
       define(facade, name, win[name].bind(win));
 
@@ -1,19 +1,29 @@
 // @vitest-environment jsdom
 import assert from "node:assert/strict";
-import { test } from "vitest";
+import { afterEach, test } from "vitest";
 
 import {
   createToolbar,
   installLocalStorage,
   installMatchMedia,
   renderToolbar,
+  teardownToolbars,
   toolbarPayload,
 } from "./toolbar-element-harness.js";
 
 var storage = installLocalStorage({ "yii-debug-toolbar-expanded": "1" });
 
 installMatchMedia();
 
+/**
+ * Detaches the fixtures and restores the expanded flag unconditionally: a
+ * thrown assertion must not hand the next test a collapsed bar.
+ */
+afterEach(() => {
+  teardownToolbars();
+  storage.set("yii-debug-toolbar-expanded", "1");
+});
+
 function request(overrides) {
   return Object.assign(
     {
 
@@ -1,20 +1,30 @@
 // @vitest-environment jsdom
 import assert from "node:assert/strict";
-import { test } from "vitest";
+import { afterEach, test } from "vitest";
 
 import {
   installLocalStorage,
   installMatchMedia,
   renderToolbar,
   stubBoundingHeight,
   stubViewportHeight,
+  teardownToolbars,
   toolbarPayload,
 } from "./toolbar-element-harness.js";
 
 var storage = installLocalStorage({ "yii-debug-toolbar-expanded": "1" });
 
 installMatchMedia();
 
+/**
+ * Detaches the fixtures and restores the expanded flag, which the collapse
+ * control persists as part of the behaviour under test.
+ */
+afterEach(() => {
+  teardownToolbars();
+  storage.set("yii-debug-toolbar-expanded", "1");
+});
+
 function payload(overrides) {
   return toolbarPayload(
     Object.assign(
 
@@ -1,17 +1,21 @@
 // @vitest-environment jsdom
 import assert from "node:assert/strict";
-import { test } from "vitest";
+import { afterEach, test } from "vitest";
 
 import {
   installLocalStorage,
   installMatchMedia,
   renderToolbar,
+  teardownToolbars,
   toolbarPayload,
 } from "./toolbar-element-harness.js";
 
 installLocalStorage({ "yii-debug-toolbar-expanded": "1" });
 installMatchMedia();
 
+/** Detaches the fixtures a thrown assertion would leave connected. */
+afterEach(teardownToolbars);
+
 function payload(overrides) {
   return toolbarPayload(
     Object.assign(
 
@@ -134,6 +134,30 @@ export function installXmlHttpRequest() {
   };
 }
 
+/**
+ * Fixtures this module attached to the document, in attachment order.
+ *
+ * Only what the harness appends is recorded: a detached `createToolbar()`
+ * fixture stays out of it, so the lifecycle tests keep driving
+ * `disconnectedCallback()` themselves.
+ */
+var attached = [];
+
+/**
+ * Detaches every recorded fixture still in the document and forgets all of
+ * them, so a thrown assertion cannot leave a connected toolbar registered in
+ * `toolbars`, listening on the document or holding a theme observer.
+ */
+export function teardownToolbars() {
+  for (var i = attached.length - 1; i >= 0; i--) {
+    if (attached[i].isConnected) {
+      attached[i].remove();
+    }
+  }
+
+  attached.length = 0;
+}
+
 export function defineToolbar() {
   if (!window.customElements.get(tagName)) {
     window.customElements.define(tagName, YiiDebugToolbar);
@@ -159,6 +183,7 @@ export function connectToolbar(attributes) {
   var element = createToolbar(attributes);
 
   document.body.appendChild(element);
+  attached.push(element);
 
   return element;
 }
@@ -212,6 +237,7 @@ export function stubFrameWindow(frame) {
   var donor = document.createElement("iframe");
 
   document.body.appendChild(donor);
+  attached.push(donor);
   Object.defineProperty(frame, "contentWindow", {
     configurable: true,
     value: donor.contentWindow,
 
@@ -1,6 +1,6 @@
 // @vitest-environment jsdom
 import assert from "node:assert/strict";
-import { test, vi } from "vitest";
+import { afterEach, test, vi } from "vitest";
 
 import { toolbars } from "../src/toolbar/state.js";
 import {
@@ -9,11 +9,27 @@ import {
   installMatchMedia,
   removeMatchMedia,
   renderToolbar,
+  teardownToolbars,
   toolbarPayload,
 } from "./toolbar-element-harness.js";
 
+var mutationObserver = window.MutationObserver;
+
 installLocalStorage({ "yii-debug-toolbar-expanded": "1" });
 
+/**
+ * Restores what a thrown assertion would leave behind: a connected toolbar, a
+ * fake clock, the deleted `MutationObserver` and the removed media query. The
+ * detached `createToolbar()` fixtures stay untouched, so the tests that drive
+ * `disconnectedCallback()` themselves keep proving what it does.
+ */
+afterEach(() => {
+  teardownToolbars();
+  vi.useRealTimers();
+  window.MutationObserver = mutationObserver;
+  installMatchMedia();
+});
+
 function payload() {
   return toolbarPayload({
     items: [
 
@@ -1,31 +1,35 @@
 // @vitest-environment jsdom
 import assert from "node:assert/strict";
-import { test, vi } from "vitest";
+import { afterEach, test, vi } from "vitest";
 
 import {
+  connectToolbar,
   createToolbar,
   installLocalStorage,
   installMatchMedia,
   installXmlHttpRequest,
+  teardownToolbars,
 } from "./toolbar-element-harness.js";
 
 installLocalStorage({ "yii-debug-toolbar-expanded": "1" });
 installMatchMedia();
 
 var transport = installXmlHttpRequest();
 
+/** Detaches the fixtures and drops a fake clock a thrown assertion left set. */
+afterEach(() => {
+  teardownToolbars();
+  vi.useRealTimers();
+});
+
 var snapshot = JSON.stringify({
   items: [{ id: "db", title: "Database", url: "/debug/db" }],
   tag: "tag-1",
   title: "Yii Debugger",
 });
 
 function mount(attributes) {
-  var element = createToolbar(attributes);
-
-  document.body.appendChild(element);
-
-  return element;
+  return connectToolbar(attributes);
 }
 
 function errorMessage(element) {
 
@@ -1,19 +1,23 @@
 // @vitest-environment jsdom
 import assert from "node:assert/strict";
-import { test } from "vitest";
+import { afterEach, test } from "vitest";
 
 import {
   createToolbar,
   installLocalStorage,
   installMatchMedia,
   renderToolbar,
+  teardownToolbars,
   toolbarPayload,
 } from "./toolbar-element-harness.js";
 
 var storage = installLocalStorage();
 
 installMatchMedia();
 
+/** Detaches the fixtures a thrown assertion would leave connected. */
+afterEach(teardownToolbars);
+
 function expanded() {
   storage.set("yii-debug-toolbar-expanded", "1");
 }