diff -r 000000000000 -r 6474c204b198 browser/devtools/debugger/test/browser_dbg_pretty-print-05.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/debugger/test/browser_dbg_pretty-print-05.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,76 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Make sure that prettifying HTML sources doesn't do anything.
+ */
+
+const TAB_URL = EXAMPLE_URL + "doc_included-script.html";
+
+let gTab, gDebuggee, gPanel, gDebugger;
+let gEditor, gSources, gControllerSources;
+
+function test() {
+  initDebugger(TAB_URL).then(([aTab, aDebuggee, aPanel]) => {
+    gTab = aTab;
+    gDebuggee = aDebuggee;
+    gPanel = aPanel;
+    gDebugger = gPanel.panelWin;
+    gEditor = gDebugger.DebuggerView.editor;
+    gSources = gDebugger.DebuggerView.Sources;
+    gControllerSources = gDebugger.DebuggerController.SourceScripts;
+
+    Task.spawn(function() {
+      yield waitForSourceShown(gPanel, TAB_URL);
+
+      // From this point onward, the source editor's text should never change.
+      gEditor.once("change", () => {
+        ok(false, "The source editor text shouldn't have changed.");
+      });
+
+      is(gSources.selectedValue, TAB_URL,
+        "The correct source is currently selected.");
+      ok(gEditor.getText().contains("myFunction"),
+        "The source shouldn't be pretty printed yet.");
+
+      clickPrettyPrintButton();
+
+      let { source } = gSources.selectedItem.attachment;
+      try {
+        yield gControllerSources.togglePrettyPrint(source);
+        ok(false, "The promise for a prettified source should be rejected!");
+      } catch ([source, error]) {
+        is(error, "Can't prettify non-javascript files.",
+          "The promise was correctly rejected with a meaningful message.");
+      }
+
+      let [source, text] = yield gControllerSources.getText(source);
+      is(gSources.selectedValue, TAB_URL,
+        "The correct source is still selected.");
+      ok(gEditor.getText().contains("myFunction"),
+        "The displayed source hasn't changed.");
+      ok(text.contains("myFunction"),
+        "The cached source text wasn't altered in any way.");
+
+      yield closeDebuggerAndFinish(gPanel);
+    });
+  });
+}
+
+function clickPrettyPrintButton() {
+  gDebugger.document.getElementById("pretty-print").click();
+}
+
+function prepareDebugger(aPanel) {
+  aPanel._view.Sources.preferredSource = TAB_URL;
+}
+
+registerCleanupFunction(function() {
+  gTab = null;
+  gDebuggee = null;
+  gPanel = null;
+  gDebugger = null;
+  gEditor = null;
+  gSources = null;
+  gControllerSources = null;
+});