diff -r 000000000000 -r 6474c204b198 browser/devtools/webconsole/test/browser_output_longstring_expand.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/webconsole/test/browser_output_longstring_expand.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,93 @@
+/* vim:set ts=2 sw=2 sts=2 et: */
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Test that long strings can be expanded in the console output.
+
+function test()
+{
+  waitForExplicitFinish();
+
+  let tempScope = {};
+  Cu.import("resource://gre/modules/devtools/dbg-server.jsm", tempScope);
+  let DebuggerServer = tempScope.DebuggerServer;
+
+  let longString = (new Array(DebuggerServer.LONG_STRING_LENGTH + 4)).join("a") +
+                   "foobar";
+  let initialString =
+    longString.substring(0, DebuggerServer.LONG_STRING_INITIAL_LENGTH);
+
+  addTab("data:text/html;charset=utf8,test for bug 787981 - check that long strings can be expanded in the output.");
+
+  let hud = null;
+
+  gBrowser.selectedBrowser.addEventListener("load", function onLoad() {
+    gBrowser.selectedBrowser.removeEventListener("load", onLoad, true);
+    openConsole(null, performTest);
+  }, true);
+
+  function performTest(aHud)
+  {
+    hud = aHud;
+    hud.jsterm.clearOutput(true);
+    hud.jsterm.execute("console.log('bazbaz', '" + longString +"', 'boom')");
+
+    waitForMessages({
+      webconsole: hud,
+      messages: [{
+        name: "console.log output",
+        text: ["bazbaz", "boom", initialString],
+        noText: "foobar",
+        longString: true,
+      }],
+    }).then(onConsoleMessage);
+  }
+
+  function onConsoleMessage([result])
+  {
+    let clickable = result.longStrings[0];
+    ok(clickable, "long string ellipsis is shown");
+
+    clickable.scrollIntoView(false);
+
+    EventUtils.synthesizeMouse(clickable, 2, 2, {}, hud.iframeWindow);
+
+    waitForMessages({
+      webconsole: hud,
+      messages: [{
+        name: "full string",
+        text: ["bazbaz", "boom", longString],
+        category: CATEGORY_WEBDEV,
+        longString: false,
+      }],
+    }).then(() => {
+      hud.jsterm.clearOutput(true);
+      hud.jsterm.execute("'" + longString +"'", onExecute);
+    });
+  }
+
+  function onExecute(msg)
+  {
+    isnot(msg.textContent.indexOf(initialString), -1,
+        "initial string is shown");
+    is(msg.textContent.indexOf(longString), -1,
+        "full string is not shown");
+
+    let clickable = msg.querySelector(".longStringEllipsis");
+    ok(clickable, "long string ellipsis is shown");
+
+    clickable.scrollIntoView(false);
+
+    EventUtils.synthesizeMouse(clickable, 3, 4, {}, hud.iframeWindow);
+
+    waitForMessages({
+      webconsole: hud,
+      messages: [{
+        name: "full string",
+        text: longString,
+        category: CATEGORY_OUTPUT,
+        longString: false,
+      }],
+    }).then(finishTest);
+  }
+}