gecko/testing/xpcshell/head.js

/* -*- Mode: JavaScript; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/. */

/*
 * This file contains common code that is loaded before each test file(s).
 * See http://developer.mozilla.org/en/docs/Writing_xpcshell-based_unit_tests
 * for more information.
 */

var _quit = false;
var _passed = true;
var _tests_pending = 0;
var _passedChecks = 0, _falsePassedChecks = 0;
var _todoChecks = 0;
var _cleanupFunctions = [];
var _pendingTimers = [];

function _dump(str) {
  let start = /^TEST-/.test(str) ? "\n" : "";
  if (typeof _XPCSHELL_PROCESS == "undefined") {
    dump(start + str);
  } else {
    dump(start + _XPCSHELL_PROCESS + ": " + str);
  }
}

// Disable automatic network detection, so tests work correctly when
// not connected to a network.
let (ios = Components.classes["@mozilla.org/network/io-service;1"]
           .getService(Components.interfaces.nsIIOService2)) {
  ios.manageOfflineStatus = false;
  ios.offline = false;
}

// Disable IPv6 lookups for 'localhost' on windows.
try {
  if ("@mozilla.org/windows-registry-key;1" in Components.classes) {
    let processType = Components.classes["@mozilla.org/xre/runtime;1"].
      getService(Components.interfaces.nsIXULRuntime).processType;
    if (processType == Components.interfaces.nsIXULRuntime.PROCESS_TYPE_DEFAULT) {
      let (prefs = Components.classes["@mozilla.org/preferences-service;1"]
                   .getService(Components.interfaces.nsIPrefBranch)) {
        prefs.setCharPref("network.dns.ipv4OnlyDomains", "localhost");
      }
    }
  }
}
catch (e) { }

// Enable crash reporting, if possible
// We rely on the Python harness to set MOZ_CRASHREPORTER_NO_REPORT
// and handle checking for minidumps.
// Note that if we're in a child process, we don't want to init the
// crashreporter component.
try { // nsIXULRuntime is not available in some configurations.
  let processType = Components.classes["@mozilla.org/xre/runtime;1"].
    getService(Components.interfaces.nsIXULRuntime).processType;
  if (processType == Components.interfaces.nsIXULRuntime.PROCESS_TYPE_DEFAULT &&
      "@mozilla.org/toolkit/crash-reporter;1" in Components.classes) {
    // Remember to update </toolkit/crashreporter/test/unit/test_crashreporter.js>
    // too if you change this initial setting.
    let (crashReporter =
          Components.classes["@mozilla.org/toolkit/crash-reporter;1"]
          .getService(Components.interfaces.nsICrashReporter)) {
      crashReporter.enabled = true;
      crashReporter.minidumpPath = do_get_cwd();
    }
  }
}
catch (e) { }

/**
 * Date.now() is not necessarily monotonically increasing (insert sob story
 * about times not being the right tool to use for measuring intervals of time,
 * robarnold can tell all), so be wary of error by erring by at least
 * _timerFuzz ms.
 */
const _timerFuzz = 15;

function _Timer(func, delay) {
  delay = Number(delay);
  if (delay < 0)
    do_throw("do_timeout() delay must be nonnegative");

  if (typeof func !== "function")
    do_throw("string callbacks no longer accepted; use a function!");

  this._func = func;
  this._start = Date.now();
  this._delay = delay;

  var timer = Components.classes["@mozilla.org/timer;1"]
                        .createInstance(Components.interfaces.nsITimer);
  timer.initWithCallback(this, delay + _timerFuzz, timer.TYPE_ONE_SHOT);

  // Keep timer alive until it fires
  _pendingTimers.push(timer);
}
_Timer.prototype = {
  QueryInterface: function(iid) {
    if (iid.Equals(Components.interfaces.nsITimerCallback) ||
        iid.Equals(Components.interfaces.nsISupports))
      return this;

    throw Components.results.NS_ERROR_NO_INTERFACE;
  },

  notify: function(timer) {
    _pendingTimers.splice(_pendingTimers.indexOf(timer), 1);

    // The current nsITimer implementation can undershoot, but even if it
    // couldn't, paranoia is probably a virtue here given the potential for
    // random orange on tinderboxen.
    var end = Date.now();
    var elapsed = end - this._start;
    if (elapsed >= this._delay) {
      try {
        this._func.call(null);
      } catch (e) {
        do_throw("exception thrown from do_timeout callback: " + e);
      }
      return;
    }

    // Timer undershot, retry with a little overshoot to try to avoid more
    // undershoots.
    var newDelay = this._delay - elapsed;
    do_timeout(newDelay, this._func);
  }
};

function _do_main() {
  if (_quit)
    return;

  _dump("TEST-INFO | (xpcshell/head.js) | running event loop\n");

  var thr = Components.classes["@mozilla.org/thread-manager;1"]
                      .getService().currentThread;

  while (!_quit)
    thr.processNextEvent(true);

  while (thr.hasPendingEvents())
    thr.processNextEvent(true);
}

function _do_quit() {
  _dump("TEST-INFO | (xpcshell/head.js) | exiting test\n");

  _quit = true;
}

function _dump_exception_stack(stack) {
  stack.split("\n").forEach(function(frame) {
    if (!frame)
      return;
    // frame is of the form "fname(args)@file:line"
    let frame_regexp = new RegExp("(.*)\\(.*\\)@(.*):(\\d*)", "g");
    let parts = frame_regexp.exec(frame);
    if (parts)
        dump("JS frame :: " + parts[2] + " :: " + (parts[1] ? parts[1] : "anonymous")
             + " :: line " + parts[3] + "\n");
    else /* Could be a -e (command line string) style location. */
        dump("JS frame :: " + frame + "\n");
  });
}

/**
 * Overrides idleService with a mock.  Idle is commonly used for maintenance
 * tasks, thus if a test uses a service that requires the idle service, it will
 * start handling them.
 * This behaviour would cause random failures and slowdown tests execution,
 * for example by running database vacuum or cleanups for each test.
 *
 * @note Idle service is overridden by default.  If a test requires it, it will
 *       have to call do_get_idle() function at least once before use.
 */
_fakeIdleService = {
  get registrar() {
    delete this.registrar;
    return this.registrar =
      Components.manager.QueryInterface(Components.interfaces.nsIComponentRegistrar);
  },
  contractID: "@mozilla.org/widget/idleservice;1",
  get CID() this.registrar.contractIDToCID(this.contractID),

  activate: function FIS_activate()
  {
    if (!this.originalFactory) {
      // Save original factory.
      this.originalFactory =
        Components.manager.getClassObject(Components.classes[this.contractID],
                                          Components.interfaces.nsIFactory);
      // Unregister original factory.
      this.registrar.unregisterFactory(this.CID, this.originalFactory);
      // Replace with the mock.
      this.registrar.registerFactory(this.CID, "Fake Idle Service",
                                     this.contractID, this.factory
      );
    }
  },

  deactivate: function FIS_deactivate()
  {
    if (this.originalFactory) {
      // Unregister the mock.
      this.registrar.unregisterFactory(this.CID, this.factory);
      // Restore original factory.
      this.registrar.registerFactory(this.CID, "Idle Service",
                                     this.contractID, this.originalFactory);
      delete this.originalFactory;
    }
  },

  factory: {
    // nsIFactory
    createInstance: function (aOuter, aIID)
    {
      if (aOuter) {
        throw Components.results.NS_ERROR_NO_AGGREGATION;
      }
      return _fakeIdleService.QueryInterface(aIID);
    },
    lockFactory: function (aLock) {
      throw Components.results.NS_ERROR_NOT_IMPLEMENTED;
    },
    QueryInterface: function(aIID) {
      if (aIID.equals(Components.interfaces.nsIFactory) ||
          aIID.equals(Components.interfaces.nsISupports)) {
        return this;
      }
      throw Components.results.NS_ERROR_NO_INTERFACE;
    }
  },

  // nsIIdleService
  get idleTime() 0,
  addIdleObserver: function () {},
  removeIdleObserver: function () {},

  QueryInterface: function(aIID) {
    // Useful for testing purposes, see test_get_idle.js.
    if (aIID.equals(Components.interfaces.nsIFactory)) {
      return this.factory;
    }
    if (aIID.equals(Components.interfaces.nsIIdleService) ||
        aIID.equals(Components.interfaces.nsISupports)) {
      return this;
    }
    throw Components.results.NS_ERROR_NO_INTERFACE;
  }
}

/**
 * Restores the idle service factory if needed and returns the service's handle.
 * @return A handle to the idle service.
 */
function do_get_idle() {
  _fakeIdleService.deactivate();
  return Components.classes[_fakeIdleService.contractID]
                   .getService(Components.interfaces.nsIIdleService);
}

// Map resource://test/ to current working directory and
// resource://testing-common/ to the shared test modules directory.
function _register_protocol_handlers() {
  let (ios = Components.classes["@mozilla.org/network/io-service;1"]
             .getService(Components.interfaces.nsIIOService)) {
    let protocolHandler =
      ios.getProtocolHandler("resource")
         .QueryInterface(Components.interfaces.nsIResProtocolHandler);
    let curDirURI = ios.newFileURI(do_get_cwd());
    protocolHandler.setSubstitution("test", curDirURI);

    if (this._TESTING_MODULES_DIR) {
      let modulesFile = Components.classes["@mozilla.org/file/local;1"].
                        createInstance(Components.interfaces.nsILocalFile);
      modulesFile.initWithPath(_TESTING_MODULES_DIR);

      let modulesURI = ios.newFileURI(modulesFile);
      protocolHandler.setSubstitution("testing-common", modulesURI);
    }
  }
}

function _execute_test() {
  _register_protocol_handlers();

  // Override idle service by default.
  // Call do_get_idle() to restore the factory and get the service.
  _fakeIdleService.activate();

  // _HEAD_FILES is dynamically defined by <runxpcshelltests.py>.
  _load_files(_HEAD_FILES);
  // _TEST_FILE is dynamically defined by <runxpcshelltests.py>.
  _load_files(_TEST_FILE);

  try {
    do_test_pending();
    run_test();
    do_test_finished();
    _do_main();
  } catch (e) {
    _passed = false;
    // do_check failures are already logged and set _quit to true and throw
    // NS_ERROR_ABORT. If both of those are true it is likely this exception
    // has already been logged so there is no need to log it again. It's
    // possible that this will mask an NS_ERROR_ABORT that happens after a
    // do_check failure though.
    if (!_quit || e != Components.results.NS_ERROR_ABORT) {
      msg = "TEST-UNEXPECTED-FAIL | ";
      if (e.fileName) {
        msg += e.fileName;
        if (e.lineNumber) {
          msg += ":" + e.lineNumber;
        }
      } else {
        msg += "xpcshell/head.js";
      }
      msg += " | " + e;
      if (e.stack) {
        _dump(msg + " - See following stack:\n");
        _dump_exception_stack(e.stack);
      }
      else {
        _dump(msg + "\n");
      }
    }
  }

  // _TAIL_FILES is dynamically defined by <runxpcshelltests.py>.
  _load_files(_TAIL_FILES);

  // Execute all of our cleanup functions.
  var func;
  while ((func = _cleanupFunctions.pop()))
    func();

  // Restore idle service to avoid leaks.
  _fakeIdleService.deactivate();

  if (!_passed)
    return;

  var truePassedChecks = _passedChecks - _falsePassedChecks;
  if (truePassedChecks > 0) {
    _dump("TEST-PASS | (xpcshell/head.js) | " + truePassedChecks + " (+ " +
            _falsePassedChecks + ") check(s) passed\n");
    _dump("TEST-INFO | (xpcshell/head.js) | " + _todoChecks +
            " check(s) todo\n");
  } else {
    // ToDo: switch to TEST-UNEXPECTED-FAIL when all tests have been updated. (Bug 496443)
    _dump("TEST-INFO | (xpcshell/head.js) | No (+ " + _falsePassedChecks + ") checks actually run\n");
  }
}

/**
 * Loads files.
 *
 * @param aFiles Array of files to load.
 */
function _load_files(aFiles) {
  function loadTailFile(element, index, array) {
    load(element);
  }

  aFiles.forEach(loadTailFile);
}


/************** Functions to be used from the tests **************/

/**
 * Prints a message to the output log.
 */
function do_print(msg) {
  var caller_stack = Components.stack.caller;
  _dump("TEST-INFO | " + caller_stack.filename + " | " + msg + "\n");
}

/**
 * Calls the given function at least the specified number of milliseconds later.
 * The callback will not undershoot the given time, but it might overshoot --
 * don't expect precision!
 *
 * @param delay : uint
 *   the number of milliseconds to delay
 * @param callback : function() : void
 *   the function to call
 */
function do_timeout(delay, func) {
  new _Timer(func, Number(delay));
}

function do_execute_soon(callback) {
  do_test_pending();
  var tm = Components.classes["@mozilla.org/thread-manager;1"]
                     .getService(Components.interfaces.nsIThreadManager);

  tm.mainThread.dispatch({
    run: function() {
      try {
        callback();
      } catch (e) {
        // do_check failures are already logged and set _quit to true and throw
        // NS_ERROR_ABORT. If both of those are true it is likely this exception
        // has already been logged so there is no need to log it again. It's
        // possible that this will mask an NS_ERROR_ABORT that happens after a
        // do_check failure though.
        if (!_quit || e != Components.results.NS_ERROR_ABORT) {
          _dump("TEST-UNEXPECTED-FAIL | (xpcshell/head.js) | " + e);
          if (e.stack) {
            dump(" - See following stack:\n");
            _dump_exception_stack(e.stack);
          }
          else {
            dump("\n");
          }
          _do_quit();
        }
      }
      finally {
        do_test_finished();
      }
    }
  }, Components.interfaces.nsIThread.DISPATCH_NORMAL);
}

function do_throw(text, stack) {
  if (!stack)
    stack = Components.stack.caller;

  _passed = false;
  _dump("TEST-UNEXPECTED-FAIL | " + stack.filename + " | " + text +
        " - See following stack:\n");
  var frame = Components.stack;
  while (frame != null) {
    _dump(frame + "\n");
    frame = frame.caller;
  }

  _do_quit();
  throw Components.results.NS_ERROR_ABORT;
}

function do_throw_todo(text, stack) {
  if (!stack)
    stack = Components.stack.caller;

  _passed = false;
  _dump("TEST-UNEXPECTED-PASS | " + stack.filename + " | " + text +
        " - See following stack:\n");
  var frame = Components.stack;
  while (frame != null) {
    _dump(frame + "\n");
    frame = frame.caller;
  }

  _do_quit();
  throw Components.results.NS_ERROR_ABORT;
}

function do_report_unexpected_exception(ex, text) {
  var caller_stack = Components.stack.caller;
  text = text ? text + " - " : "";

  _passed = false;
  _dump("TEST-UNEXPECTED-FAIL | " + caller_stack.filename + " | " + text +
        "Unexpected exception " + ex + ", see following stack:\n" + ex.stack +
        "\n");

  _do_quit();
  throw Components.results.NS_ERROR_ABORT;
}

function do_note_exception(ex, text) {
  var caller_stack = Components.stack.caller;
  text = text ? text + " - " : "";

  _dump("TEST-INFO | " + caller_stack.filename + " | " + text +
        "Swallowed exception " + ex + ", see following stack:\n" + ex.stack +
        "\n");
}

function _do_check_neq(left, right, stack, todo) {
  if (!stack)
    stack = Components.stack.caller;

  var text = left + " != " + right;
  if (left == right) {
    if (!todo) {
      do_throw(text, stack);
    } else {
      ++_todoChecks;
      _dump("TEST-KNOWN-FAIL | " + stack.filename + " | [" + stack.name +
            " : " + stack.lineNumber + "] " + text +"\n");
    }
  } else {
    if (!todo) {
      ++_passedChecks;
      _dump("TEST-PASS | " + stack.filename + " | [" + stack.name + " : " +
            stack.lineNumber + "] " + text + "\n");
    } else {
      do_throw_todo(text, stack);
    }
  }
}

function do_check_neq(left, right, stack) {
  if (!stack)
    stack = Components.stack.caller;

  _do_check_neq(left, right, stack, false);
}

function todo_check_neq(left, right, stack) {
  if (!stack)
      stack = Components.stack.caller;

  _do_check_neq(left, right, stack, true);
}

function _do_check_eq(left, right, stack, todo) {
  if (!stack)
    stack = Components.stack.caller;

  var text = left + " == " + right;
  if (left != right) {
    if (!todo) {
      do_throw(text, stack);
    } else {
      ++_todoChecks;
      _dump("TEST-KNOWN-FAIL | " + stack.filename + " | [" + stack.name +
            " : " + stack.lineNumber + "] " + text +"\n");
    }
  } else {
    if (!todo) {
      ++_passedChecks;
      _dump("TEST-PASS | " + stack.filename + " | [" + stack.name + " : " +
            stack.lineNumber + "] " + text + "\n");
    } else {
      do_throw_todo(text, stack);
    }
  }
}

function do_check_eq(left, right, stack) {
  if (!stack)
    stack = Components.stack.caller;

  _do_check_eq(left, right, stack, false);
}

function todo_check_eq(left, right, stack) {
  if (!stack)
      stack = Components.stack.caller;

  _do_check_eq(left, right, stack, true);
}

function do_check_true(condition, stack) {
  if (!stack)
    stack = Components.stack.caller;

  do_check_eq(condition, true, stack);
}

function todo_check_true(condition, stack) {
  if (!stack)
    stack = Components.stack.caller;

  todo_check_eq(condition, true, stack);
}

function do_check_false(condition, stack) {
  if (!stack)
    stack = Components.stack.caller;

  do_check_eq(condition, false, stack);
}

function todo_check_false(condition, stack) {
  if (!stack)
    stack = Components.stack.caller;

  todo_check_eq(condition, false, stack);
}

function do_check_null(condition, stack=Components.stack.caller) {
  do_check_eq(condition, null, stack);
}

function todo_check_null(condition, stack=Components.stack.caller) {
  todo_check_eq(condition, null, stack);
}

function do_test_pending() {
  ++_tests_pending;

  _dump("TEST-INFO | (xpcshell/head.js) | test " + _tests_pending +
         " pending\n");
}

function do_test_finished() {
  _dump("TEST-INFO | (xpcshell/head.js) | test " + _tests_pending +
         " finished\n");

  if (--_tests_pending == 0)
    _do_quit();
}

function do_get_file(path, allowNonexistent) {
  try {
    let lf = Components.classes["@mozilla.org/file/directory_service;1"]
      .getService(Components.interfaces.nsIProperties)
      .get("CurWorkD", Components.interfaces.nsILocalFile);

    let bits = path.split("/");
    for (let i = 0; i < bits.length; i++) {
      if (bits[i]) {
        if (bits[i] == "..")
          lf = lf.parent;
        else
          lf.append(bits[i]);
      }
    }

    if (!allowNonexistent && !lf.exists()) {
      // Not using do_throw(): caller will continue.
      _passed = false;
      var stack = Components.stack.caller;
      _dump("TEST-UNEXPECTED-FAIL | " + stack.filename + " | [" +
            stack.name + " : " + stack.lineNumber + "] " + lf.path +
            " does not exist\n");
    }

    return lf;
  }
  catch (ex) {
    do_throw(ex.toString(), Components.stack.caller);
  }

  return null;
}

// do_get_cwd() isn't exactly self-explanatory, so provide a helper
function do_get_cwd() {
  return do_get_file("");
}

/**
 * Loads _HTTPD_JS_PATH file, which is dynamically defined by
 * <runxpcshelltests.py>.
 */
function do_load_httpd_js() {
  load(_HTTPD_JS_PATH);
}

function do_load_manifest(path) {
  var lf = do_get_file(path);
  const nsIComponentRegistrar = Components.interfaces.nsIComponentRegistrar;
  do_check_true(Components.manager instanceof nsIComponentRegistrar);
  // Previous do_check_true() is not a test check.
  ++_falsePassedChecks;
  Components.manager.autoRegister(lf);
}

/**
 * Parse a DOM document.
 *
 * @param aPath File path to the document.
 * @param aType Content type to use in DOMParser.
 *
 * @return nsIDOMDocument from the file.
 */
function do_parse_document(aPath, aType) {
  switch (aType) {
    case "application/xhtml+xml":
    case "application/xml":
    case "text/xml":
      break;

    default:
      do_throw("type: expected application/xhtml+xml, application/xml or text/xml," +
                 " got '" + aType + "'",
               Components.stack.caller);
  }

  var lf = do_get_file(aPath);
  const C_i = Components.interfaces;
  const parserClass = "@mozilla.org/xmlextras/domparser;1";
  const streamClass = "@mozilla.org/network/file-input-stream;1";
  var stream = Components.classes[streamClass]
                         .createInstance(C_i.nsIFileInputStream);
  stream.init(lf, -1, -1, C_i.nsIFileInputStream.CLOSE_ON_EOF);
  var parser = Components.classes[parserClass]
                         .createInstance(C_i.nsIDOMParser);
  var doc = parser.parseFromStream(stream, null, lf.fileSize, aType);
  parser = null;
  stream = null;
  lf = null;
  return doc;
}

/**
 * Registers a function that will run when the test harness is done running all
 * tests.
 *
 * @param aFunction
 *        The function to be called when the test harness has finished running.
 */
function do_register_cleanup(aFunction)
{
  _cleanupFunctions.push(aFunction);
}

/**
 * Registers a directory with the profile service,
 * and return the directory as an nsILocalFile.
 *
 * @return nsILocalFile of the profile directory.
 */
function do_get_profile() {
  // Since we have a profile, we will notify profile shutdown topics at
  // the end of the current test, to ensure correct cleanup on shutdown.
  do_register_cleanup(function() {
    let obsSvc = Components.classes["@mozilla.org/observer-service;1"].
                 getService(Components.interfaces.nsIObserverService);
    obsSvc.notifyObservers(null, "profile-change-net-teardown", null);
    obsSvc.notifyObservers(null, "profile-change-teardown", null);
    obsSvc.notifyObservers(null, "profile-before-change", null);
  });

  let env = Components.classes["@mozilla.org/process/environment;1"]
                      .getService(Components.interfaces.nsIEnvironment);
  // the python harness sets this in the environment for us
  let profd = env.get("XPCSHELL_TEST_PROFILE_DIR");
  let file = Components.classes["@mozilla.org/file/local;1"]
                       .createInstance(Components.interfaces.nsILocalFile);
  file.initWithPath(profd);

  let dirSvc = Components.classes["@mozilla.org/file/directory_service;1"]
                         .getService(Components.interfaces.nsIProperties);
  let provider = {
    getFile: function(prop, persistent) {
      persistent.value = true;
      if (prop == "ProfD" || prop == "ProfLD" || prop == "ProfDS" ||
          prop == "ProfLDS" || prop == "TmpD") {
        return file.clone();
      }
      throw Components.results.NS_ERROR_FAILURE;
    },
    QueryInterface: function(iid) {
      if (iid.equals(Components.interfaces.nsIDirectoryServiceProvider) ||
          iid.equals(Components.interfaces.nsISupports)) {
        return this;
      }
      throw Components.results.NS_ERROR_NO_INTERFACE;
    }
  };
  dirSvc.QueryInterface(Components.interfaces.nsIDirectoryService)
        .registerProvider(provider);

  // The methods of 'provider' will entrain this scope so null out everything
  // to avoid spurious leak reports.
  env = null;
  profd = null;
  dirSvc = null;
  provider = null;
  return file.clone();
}

/**
 * This function loads head.js (this file) in the child process, so that all
 * functions defined in this file (do_throw, etc) are available to subsequent
 * sendCommand calls.  It also sets various constants used by these functions.
 *
 * (Note that you may use sendCommand without calling this function first;  you
 * simply won't have any of the functions in this file available.)
 */
function do_load_child_test_harness()
{
  // Make sure this isn't called from child process
  var runtime = Components.classes["@mozilla.org/xre/app-info;1"]
                  .getService(Components.interfaces.nsIXULRuntime);
  if (runtime.processType != 
            Components.interfaces.nsIXULRuntime.PROCESS_TYPE_DEFAULT) 
  {
    do_throw("run_test_in_child cannot be called from child!");
  }

  // Allow to be called multiple times, but only run once
  if (typeof do_load_child_test_harness.alreadyRun != "undefined")
    return;
  do_load_child_test_harness.alreadyRun = 1;
  
  function addQuotes (str)  { 
    return '"' + str + '"'; 
  }
  var quoted_head_files = _HEAD_FILES.map(addQuotes);
  var quoted_tail_files = _TAIL_FILES.map(addQuotes);

  _XPCSHELL_PROCESS = "parent";

  let command =
        "const _HEAD_JS_PATH='" + _HEAD_JS_PATH + "'; "
      + "const _HTTPD_JS_PATH='" + _HTTPD_JS_PATH + "'; "
      + "const _HEAD_FILES=[" + quoted_head_files.join() + "];"
      + "const _TAIL_FILES=[" + quoted_tail_files.join() + "];"
      + "const _XPCSHELL_PROCESS='child';";

  if (this._TESTING_MODULES_DIR) {
    command += "const _TESTING_MODULES_DIR='" + _TESTING_MODULES_DIR + "'; ";
  }

  command += "load(_HEAD_JS_PATH);";

  sendCommand(command);
}

/**
 * Runs an entire xpcshell unit test in a child process (rather than in chrome,
 * which is the default).
 *
 * This function returns immediately, before the test has completed.  
 *
 * @param testFile
 *        The name of the script to run.  Path format same as load().
 * @param optionalCallback.
 *        Optional function to be called (in parent) when test on child is
 *        complete.  If provided, the function must call do_test_finished();
 */
function run_test_in_child(testFile, optionalCallback) 
{
  var callback = (typeof optionalCallback == 'undefined') ? 
                    do_test_finished : optionalCallback;

  do_load_child_test_harness();

  var testPath = do_get_file(testFile).path.replace(/\\/g, "/");
  do_test_pending();
  sendCommand("_dump('CHILD-TEST-STARTED'); "
              + "const _TEST_FILE=['" + testPath + "']; _execute_test(); "
              + "_dump('CHILD-TEST-COMPLETED');", 
              callback);
}


/**
 * Add a test function to the list of tests that are to be run asynchronously.
 *
 * Each test function must call run_next_test() when it's done. Test files
 * should call run_next_test() in their run_test function to execute all
 * async tests.
 *
 * @return the test function that was passed in.
 */
let gTests = [];
function add_test(func) {
  gTests.push(func);
  return func;
}

/**
 * Runs the next test function from the list of async tests.
 */
let gRunningTest = null;
let gTestIndex = 0; // The index of the currently running test.
function run_next_test()
{
  function _run_next_test()
  {
    if (gTestIndex < gTests.length) {
      do_test_pending();
      gRunningTest = gTests[gTestIndex++];
      print("TEST-INFO | " + _TEST_FILE + " | Starting " +
            gRunningTest.name);
      // Exceptions do not kill asynchronous tests, so they'll time out.
      try {
        gRunningTest();
      }
      catch (e) {
        do_throw(e);
      }
    }
  }

  // For sane stacks during failures, we execute this code soon, but not now.
  // We do this now, before we call do_test_finished(), to ensure the pending
  // counter (_tests_pending) never reaches 0 while we still have tests to run
  // (do_execute_soon bumps that counter).
  do_execute_soon(_run_next_test);

  if (gRunningTest !== null) {
    // Close the previous test do_test_pending call.
    do_test_finished();
  }
}