diff -r 000000000000 -r 6474c204b198 browser/devtools/webconsole/test/browser_webconsole_js_input_expansion.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/webconsole/test/browser_webconsole_js_input_expansion.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,60 @@
+/* vim:set ts=2 sw=2 sts=2 et: */
+/* 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/. */
+
+// Tests that the input box expands as the user types long lines.
+
+const TEST_URI = "http://example.com/browser/browser/devtools/webconsole/test/test-console.html";
+
+function test() {
+  addTab(TEST_URI);
+  browser.addEventListener("load", function onLoad() {
+    browser.removeEventListener("load", onLoad, true);
+    openConsole(null, testJSInputExpansion);
+  }, true);
+}
+
+function testJSInputExpansion(hud) {
+  let jsterm = hud.jsterm;
+  let input = jsterm.inputNode;
+  input.focus();
+
+  is(input.getAttribute("multiline"), "true", "multiline is enabled");
+  // Tests if the inputNode expands.
+  input.value = "hello\nworld\n";
+  let length = input.value.length;
+  input.selectionEnd = length;
+  input.selectionStart = length;
+  function getHeight()
+  {
+    return input.clientHeight;
+  }
+  let initialHeight = getHeight();
+  // Performs an "d". This will trigger/test for the input event that should
+  // change the "row" attribute of the inputNode.
+  EventUtils.synthesizeKey("d", {});
+  let newHeight = getHeight();
+  ok(initialHeight < newHeight, "Height changed: " + newHeight);
+
+  // Add some more rows. Tests for the 8 row limit.
+  input.value = "row1\nrow2\nrow3\nrow4\nrow5\nrow6\nrow7\nrow8\nrow9\nrow10\n";
+  length = input.value.length;
+  input.selectionEnd = length;
+  input.selectionStart = length;
+  EventUtils.synthesizeKey("d", {});
+  let newerHeight = getHeight();
+
+  ok(newerHeight > newHeight, "height changed: " + newerHeight);
+
+  // Test if the inputNode shrinks again.
+  input.value = "";
+  EventUtils.synthesizeKey("d", {});
+  let height = getHeight();
+  info("height: " + height);
+  info("initialHeight: " + initialHeight);
+  let finalHeightDifference = Math.abs(initialHeight - height);
+  ok(finalHeightDifference <= 1, "height shrank to original size within 1px");
+
+  finishTest();
+}