1 files changed, 106 insertions, 0 deletions
diff --git a/devtools/client/inspector/test/browser_inspector_pane-toggle-05.js b/devtools/client/inspector/test/browser_inspector_pane-toggle-05.js
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index 0000000000..d2653639a0
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+++ b/devtools/client/inspector/test/browser_inspector_pane-toggle-05.js
@@ -0,0 +1,106 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+// Tests whether the initial selected tab is displayed when switched from 3 pane to 2 pane
+// and back to 3 pane when no other tab is selected explicitly. Rule view is displayed
+// immediately on toggling to 2 pane.
+add_task(async function () {
+  info(
+    "Switch to 2 pane inspector and back to 3 pane to test whether the selected tab is used"
+  );
+  await pushPref("devtools.inspector.three-pane-enabled", true);
+
+  const { inspector } = await openInspectorForURL("about:blank");
+
+  inspector.sidebar.select("changesview");
+
+  is(
+    inspector.sidebar.getCurrentTabID(),
+    "changesview",
+    "Changes view should be the active sidebar"
+  );
+
+  info("Click on the toggle button to toggle OFF 3 pane inspector");
+  await toggleSidebar(inspector);
+
+  is(
+    inspector.sidebar.getCurrentTabID(),
+    "ruleview",
+    "Rules view should be the active sidebar on toggle to 2 pane"
+  );
+
+  info("Click on the toggle button to toggle ON 3 pane inspector");
+  await toggleSidebar(inspector);
+
+  is(
+    inspector.sidebar.getCurrentTabID(),
+    "changesview",
+    "Changes view should be the active sidebar again"
+  );
+});
+
+// Tests whether the selected pane in 2 pane view is also used after toggling to 3 pane view.
+add_task(async function () {
+  info("Switch to 3 pane to test whether the selected pane is preserved");
+  await pushPref("devtools.inspector.three-pane-enabled", false);
+
+  const { inspector } = await openInspectorForURL("about:blank");
+
+  inspector.sidebar.select("changesview");
+
+  is(
+    inspector.sidebar.getCurrentTabID(),
+    "changesview",
+    "Changes view should be the active sidebar"
+  );
+
+  info("Click on the toggle button to toggle ON 3 pane inspector");
+  await toggleSidebar(inspector);
+
+  is(
+    inspector.sidebar.getCurrentTabID(),
+    "changesview",
+    "Changes view should still be the active sidebar"
+  );
+});
+
+// Tests whether the selected pane is layout view, if rule view is selected before toggling to 3 pane.
+add_task(async function () {
+  info("Switch to 3 pane to test whether the selected pane is layout view");
+  await pushPref("devtools.inspector.three-pane-enabled", false);
+
+  const { inspector } = await openInspectorForURL("about:blank");
+
+  inspector.sidebar.select("ruleview");
+
+  is(
+    inspector.sidebar.getCurrentTabID(),
+    "ruleview",
+    "Rules view should be the active sidebar in 2 pane"
+  );
+
+  info("Click on the toggle button to toggle ON 3 pane inspector");
+  await toggleSidebar(inspector);
+
+  is(
+    inspector.sidebar.getCurrentTabID(),
+    "layoutview",
+    "Layout view should be the active sidebar in 3 pane"
+  );
+});
+
+const toggleSidebar = async inspector => {
+  const { panelDoc: doc } = inspector;
+  const button = doc.querySelector(".sidebar-toggle");
+
+  const onRuleViewAdded = inspector.once("ruleview-added");
+  EventUtils.synthesizeMouseAtCenter(
+    button,
+    {},
+    inspector.panelDoc.defaultView
+  );
+  await onRuleViewAdded;
+};