diff -r 000000000000 -r 6474c204b198 toolkit/devtools/server/tests/unit/test_longstringactor.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/devtools/server/tests/unit/test_longstringactor.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,107 @@
+/* -*- Mode: javascript; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; js-indent-level: 2; -*- */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function run_test()
+{
+  Cu.import("resource://gre/modules/jsdebugger.jsm");
+  addDebuggerToGlobal(this);
+  let loader = Cc["@mozilla.org/moz/jssubscript-loader;1"]
+    .getService(Components.interfaces.mozIJSSubScriptLoader);
+  loader.loadSubScript("resource://gre/modules/devtools/server/actors/script.js");
+
+  test_LSA_disconnect();
+  test_LSA_grip();
+  test_LSA_onSubstring();
+}
+
+const TEST_STRING = "This is a very long string!";
+
+function makeMockLongStringActor()
+{
+  let string = TEST_STRING;
+  let actor = new LongStringActor(string);
+  actor.actorID = "longString1";
+  actor.registeredPool = {
+    longStringActors: {
+      longString1: actor
+    }
+  };
+  return actor;
+}
+
+function test_LSA_disconnect()
+{
+  let actor = makeMockLongStringActor();
+  do_check_eq(actor.registeredPool.longStringActors[actor.actorID], actor);
+
+  actor.disconnect();
+  do_check_eq(actor.registeredPool.longStringActors[actor.actorID], void 0);
+}
+
+function test_LSA_substring()
+{
+  let actor = makeMockLongStringActor();
+  do_check_eq(actor._substring(0, 4), TEST_STRING.substring(0, 4));
+  do_check_eq(actor._substring(6, 9), TEST_STRING.substring(6, 9));
+  do_check_eq(actor._substring(0, TEST_STRING.length), TEST_STRING);
+}
+
+function test_LSA_grip()
+{
+  let actor = makeMockLongStringActor();
+
+  let grip = actor.grip();
+  do_check_eq(grip.type, "longString");
+  do_check_eq(grip.initial, TEST_STRING.substring(0, DebuggerServer.LONG_STRING_INITIAL_LENGTH));
+  do_check_eq(grip.length, TEST_STRING.length);
+  do_check_eq(grip.actor, actor.actorID);
+}
+
+function test_LSA_onSubstring()
+{
+  let actor = makeMockLongStringActor();
+  let response;
+
+  // From the start
+  response = actor.onSubstring({
+    start: 0,
+    end: 4
+  });
+  do_check_eq(response.from, actor.actorID);
+  do_check_eq(response.substring, TEST_STRING.substring(0, 4));
+
+  // In the middle
+  response = actor.onSubstring({
+    start: 5,
+    end: 8
+  });
+  do_check_eq(response.from, actor.actorID);
+  do_check_eq(response.substring, TEST_STRING.substring(5, 8));
+
+  // Whole string
+  response = actor.onSubstring({
+    start: 0,
+    end: TEST_STRING.length
+  });
+  do_check_eq(response.from, actor.actorID);
+  do_check_eq(response.substring, TEST_STRING);
+
+  // Negative index
+  response = actor.onSubstring({
+    start: -5,
+    end: TEST_STRING.length
+  });
+  do_check_eq(response.from, actor.actorID);
+  do_check_eq(response.substring,
+              TEST_STRING.substring(-5, TEST_STRING.length));
+
+  // Past the end
+  response = actor.onSubstring({
+    start: TEST_STRING.length - 5,
+    end: 100
+  });
+  do_check_eq(response.from, actor.actorID);
+  do_check_eq(response.substring,
+              TEST_STRING.substring(TEST_STRING.length - 5, 100));
+}