diff -r 000000000000 -r 6474c204b198 browser/devtools/debugger/test/browser_dbg_instruments-pane-collapse.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/debugger/test/browser_dbg_instruments-pane-collapse.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,154 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Tests that the debugger panes collapse properly.
+ */
+
+const TAB_URL = EXAMPLE_URL + "doc_recursion-stack.html";
+
+let gTab, gDebuggee, gPanel, gDebugger;
+let gPrefs, gOptions;
+
+function test() {
+  initDebugger(TAB_URL).then(([aTab, aDebuggee, aPanel]) => {
+    gTab = aTab;
+    gDebuggee = aDebuggee;
+    gPanel = aPanel;
+    gDebugger = gPanel.panelWin;
+    gPrefs = gDebugger.Prefs;
+    gOptions = gDebugger.DebuggerView.Options;
+
+    testPanesState();
+
+    gDebugger.DebuggerView.toggleInstrumentsPane({ visible: true, animated: false });
+
+    testInstrumentsPaneCollapse();
+    testPanesStartupPref();
+
+    closeDebuggerAndFinish(gPanel);
+  });
+}
+
+function testPanesState() {
+  let instrumentsPane =
+    gDebugger.document.getElementById("instruments-pane");
+  let instrumentsPaneToggleButton =
+    gDebugger.document.getElementById("instruments-pane-toggle");
+
+  ok(instrumentsPane.hasAttribute("pane-collapsed") &&
+     instrumentsPaneToggleButton.hasAttribute("pane-collapsed"),
+    "The debugger view instruments pane should initially be hidden.");
+  is(gPrefs.panesVisibleOnStartup, false,
+    "The debugger view instruments pane should initially be preffed as hidden.");
+  isnot(gOptions._showPanesOnStartupItem.getAttribute("checked"), "true",
+    "The options menu item should not be checked.");
+}
+
+function testInstrumentsPaneCollapse() {
+  let instrumentsPane =
+    gDebugger.document.getElementById("instruments-pane");
+  let instrumentsPaneToggleButton =
+    gDebugger.document.getElementById("instruments-pane-toggle");
+
+  let width = parseInt(instrumentsPane.getAttribute("width"));
+  is(width, gPrefs.instrumentsWidth,
+    "The instruments pane has an incorrect width.");
+  is(instrumentsPane.style.marginLeft, "0px",
+    "The instruments pane has an incorrect left margin.");
+  is(instrumentsPane.style.marginRight, "0px",
+    "The instruments pane has an incorrect right margin.");
+  ok(!instrumentsPane.hasAttribute("animated"),
+    "The instruments pane has an incorrect animated attribute.");
+  ok(!instrumentsPane.hasAttribute("pane-collapsed") &&
+     !instrumentsPaneToggleButton.hasAttribute("pane-collapsed"),
+    "The instruments pane should at this point be visible.");
+
+  gDebugger.DebuggerView.toggleInstrumentsPane({ visible: false, animated: true });
+
+  is(gPrefs.panesVisibleOnStartup, false,
+    "The debugger view panes should still initially be preffed as hidden.");
+  isnot(gOptions._showPanesOnStartupItem.getAttribute("checked"), "true",
+    "The options menu item should still not be checked.");
+
+  let margin = -(width + 1) + "px";
+  is(width, gPrefs.instrumentsWidth,
+    "The instruments pane has an incorrect width after collapsing.");
+  is(instrumentsPane.style.marginLeft, margin,
+    "The instruments pane has an incorrect left margin after collapsing.");
+  is(instrumentsPane.style.marginRight, margin,
+    "The instruments pane has an incorrect right margin after collapsing.");
+  ok(instrumentsPane.hasAttribute("animated"),
+    "The instruments pane has an incorrect attribute after an animated collapsing.");
+  ok(instrumentsPane.hasAttribute("pane-collapsed") &&
+     instrumentsPaneToggleButton.hasAttribute("pane-collapsed"),
+    "The instruments pane should not be visible after collapsing.");
+
+  gDebugger.DebuggerView.toggleInstrumentsPane({ visible: true, animated: false });
+
+  is(gPrefs.panesVisibleOnStartup, false,
+    "The debugger view panes should still initially be preffed as hidden.");
+  isnot(gOptions._showPanesOnStartupItem.getAttribute("checked"), "true",
+    "The options menu item should still not be checked.");
+
+  is(width, gPrefs.instrumentsWidth,
+    "The instruments pane has an incorrect width after uncollapsing.");
+  is(instrumentsPane.style.marginLeft, "0px",
+    "The instruments pane has an incorrect left margin after uncollapsing.");
+  is(instrumentsPane.style.marginRight, "0px",
+    "The instruments pane has an incorrect right margin after uncollapsing.");
+  ok(!instrumentsPane.hasAttribute("animated"),
+    "The instruments pane has an incorrect attribute after an unanimated uncollapsing.");
+  ok(!instrumentsPane.hasAttribute("pane-collapsed") &&
+     !instrumentsPaneToggleButton.hasAttribute("pane-collapsed"),
+    "The instruments pane should be visible again after uncollapsing.");
+}
+
+function testPanesStartupPref() {
+  let instrumentsPane =
+    gDebugger.document.getElementById("instruments-pane");
+  let instrumentsPaneToggleButton =
+    gDebugger.document.getElementById("instruments-pane-toggle");
+
+  is(gPrefs.panesVisibleOnStartup, false,
+    "The debugger view panes should still initially be preffed as hidden.");
+
+  ok(!instrumentsPane.hasAttribute("pane-collapsed") &&
+     !instrumentsPaneToggleButton.hasAttribute("pane-collapsed"),
+    "The debugger instruments pane should at this point be visible.");
+  is(gPrefs.panesVisibleOnStartup, false,
+    "The debugger view panes should initially be preffed as hidden.");
+  isnot(gOptions._showPanesOnStartupItem.getAttribute("checked"), "true",
+    "The options menu item should still not be checked.");
+
+  gOptions._showPanesOnStartupItem.setAttribute("checked", "true");
+  gOptions._toggleShowPanesOnStartup();
+
+  ok(!instrumentsPane.hasAttribute("pane-collapsed") &&
+     !instrumentsPaneToggleButton.hasAttribute("pane-collapsed"),
+    "The debugger instruments pane should at this point be visible.");
+  is(gPrefs.panesVisibleOnStartup, true,
+    "The debugger view panes should now be preffed as visible.");
+  is(gOptions._showPanesOnStartupItem.getAttribute("checked"), "true",
+    "The options menu item should now be checked.");
+
+  gOptions._showPanesOnStartupItem.setAttribute("checked", "false");
+  gOptions._toggleShowPanesOnStartup();
+
+  ok(!instrumentsPane.hasAttribute("pane-collapsed") &&
+     !instrumentsPaneToggleButton.hasAttribute("pane-collapsed"),
+    "The debugger instruments pane should at this point be visible.");
+  is(gPrefs.panesVisibleOnStartup, false,
+    "The debugger view panes should now be preffed as hidden.");
+  isnot(gOptions._showPanesOnStartupItem.getAttribute("checked"), "true",
+    "The options menu item should now be unchecked.");
+}
+
+registerCleanupFunction(function() {
+  gTab = null;
+  gDebuggee = null;
+  gPanel = null;
+  gDebugger = null;
+  gPrefs = null;
+  gOptions = null;
+});