Fixed timing-dependent unit-tests failures

DebuggerAgent.resume unit-test should pass `done` as the callback
function, otherwise other tests may run before this one is finished.

Fixed launcher so that it runs the test callback only once, instead of
everytime a `break` event is emitted.

test/DebuggerAgent.js

@@ -227,10 +227,8 @@ describe('DebuggerAgent', function() {
     before(setupDebugScenario);
 
     it('does not throw an error', function(done) {
-      expect(function () { agent.resume(); })
+      expect(function () { agent.resume({}, done); })
         .to.not.throw();
-
-      done();
     });
 
     var debuggerClient, agent;
@@ -238,7 +236,15 @@ describe('DebuggerAgent', function() {
     function setupDebugScenario(done) {
       launcher.runOnBreakInFunction(function(client) {
         debuggerClient = client;
-        agent = new DebuggerAgent({}, null, debuggerClient, null, null);
+        var frontEndClientStub = {
+          sendEvent: function() {}
+        };
+        agent = new DebuggerAgent(
+          {},
+          frontEndClientStub,
+          debuggerClient,
+          null,  // BreakEventHandler
+          null); // ScripManager
         done();
       });
     }

test/helpers/launcher.js

@@ -44,7 +44,7 @@ function startDebugger(scriptPath, done) {
 function runOnBreakInFunction(test) {
   stopAllDebuggers();
   startDebugger('BreakInFunction.js', function(childProcess, debuggerClient) {
-    debuggerClient.on('break', function() {
+    debuggerClient.once('break', function() {
       test(debuggerClient);
     });
     childProcess.stdin.write('go!\n');
@@ -55,7 +55,7 @@ function runOnBreakInFunction(test) {
 function runInspectObject(test) {
   stopAllDebuggers();
   startDebugger('InspectObject.js', function(childProcess, debuggerClient) {
-    debuggerClient.on('break', function() {
+    debuggerClient.once('break', function() {
       debuggerClient.fetchObjectId(
         debuggerClient,
         'inspectedObject',