diff -r 000000000000 -r 6474c204b198 browser/devtools/styleeditor/test/browser_styleeditor_pretty.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/styleeditor/test/browser_styleeditor_pretty.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,49 @@
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const TESTCASE_URI = TEST_BASE + "minified.html";
+
+let gUI;
+
+function test()
+{
+  waitForExplicitFinish();
+
+  addTabAndCheckOnStyleEditorAdded(panel => gUI = panel.UI, editor => {
+    editor.getSourceEditor().then(function() {
+      testEditor(editor);
+    });
+  });
+
+  content.location = TESTCASE_URI;
+}
+
+let editorTestedCount = 0;
+function testEditor(aEditor)
+{
+  if (aEditor.styleSheet.styleSheetIndex == 0) {
+    let prettifiedSource = "body\{\r?\n\tbackground\:white;\r?\n\}\r?\n\r?\ndiv\{\r?\n\tfont\-size\:4em;\r?\n\tcolor\:red\r?\n\}\r?\n\r?\nspan\{\r?\n\tcolor\:green;\r?\n\}\r?\n";
+    let prettifiedSourceRE = new RegExp(prettifiedSource);
+
+    ok(prettifiedSourceRE.test(aEditor.sourceEditor.getText()),
+       "minified source has been prettified automatically");
+    editorTestedCount++;
+    let summary = gUI.editors[1].summary;
+    EventUtils.synthesizeMouseAtCenter(summary, {}, gPanelWindow);
+  }
+
+  if (aEditor.styleSheet.styleSheetIndex == 1) {
+    let originalSource = "body \{ background\: red; \}\r?\ndiv \{\r?\nfont\-size\: 5em;\r?\ncolor\: red\r?\n\}";
+    let originalSourceRE = new RegExp(originalSource);
+
+    ok(originalSourceRE.test(aEditor.sourceEditor.getText()),
+       "non-minified source has been left untouched");
+    editorTestedCount++;
+  }
+
+  if (editorTestedCount == 2) {
+    gUI = null;
+    finish();
+  }
+}