diff --git a/.eslintrc b/.eslintrc
index f1f99bd4..d1b1705f 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -37,6 +37,7 @@
     "CustomType": true,
     "window": true,
     "document": true,
-    "smaller": true
+    "smaller": true,
+    "wait": true
   }
 }
diff --git a/gulpfile.js b/gulpfile.js
index bbf2445d..dafa90b9 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -95,7 +95,9 @@ gulp.task("build", function () {
      .pipe(babel({
        loose: "all",
        modules: "ignore",
-       blacklist: ["regenerator"]
+       optional: ["es7.asyncFunctions"],
+       blacklist: ["regenerator"],
+       experimental: true
      }))
      .pipe(sourcemaps.write())
      .pipe(gulp.dest("."));
@@ -114,7 +116,9 @@ gulp.task("test", function () {
     .pipe(concat("jasmine"))
     .pipe(babel({
       loose: "all",
-      modules: "ignore"
+      optional: ["es7.asyncFunctions"],
+      modules: "ignore",
+      experimental: true
     }))
     .pipe(uglify())
     .pipe(sourcemaps.write())
@@ -132,7 +136,9 @@ gulp.task("build_jasmine_browser", function(){
    .pipe(babel({
      loose: "all",
      modules: "ignore",
-     blacklist: ["regenerator"]
+     optional: ["es7.asyncFunctions"],
+     blacklist: "regenerator",
+     experimental: true
    }))
    .pipe(sourcemaps.write())
    .pipe(gulp.dest("build"));
diff --git a/src/Connector.js b/src/Connector.js
index 832f580a..fffe84f7 100644
--- a/src/Connector.js
+++ b/src/Connector.js
@@ -81,22 +81,22 @@ class AbstractConnector { //eslint-disable-line no-unused-vars
   // returns false, if there is no sync target
   // true otherwise
   findNextSyncTarget () {
-    if (this.currentSyncTarget != null && this.connections[this.currentSyncTarget].isSynced === false) {
-      throw new Error("The current sync has not finished!");
+    if (this.currentSyncTarget != null) {
+      return; // "The current sync has not finished!"
     }
 
     var syncUser = null;
     for (var uid in this.connections) {
-      syncUser = this.connections[uid];
-      if (!syncUser.isSynced) {
+      if (!this.connections[uid].isSynced) {
+        syncUser = uid;
         break;
       }
     }
     if (syncUser != null){
       var conn = this;
+      this.currentSyncTarget = syncUser;
       this.y.db.requestTransaction(function*(){
-        conn.currentSyncTarget = uid;
-        conn.send(uid, {
+        conn.send(syncUser, {
           type: "sync step 1",
           stateVector: yield* this.getStateVector()
         });
@@ -110,7 +110,6 @@ class AbstractConnector { //eslint-disable-line no-unused-vars
       }
       this.whenSyncedListeners = null;
     }
-    return false;
   }
   send (uid, message) {
     if (this.debug) {
@@ -149,24 +148,38 @@ class AbstractConnector { //eslint-disable-line no-unused-vars
               type: "sync done"
             });
           }, conn.syncingClientDuration);
+        } else {
+          conn.send(sender, {
+            type: "sync done"
+          });
         }
       });
     } else if (m.type === "sync step 2") {
       this.y.db.apply(m.os);
       let conn = this;
+      var broadcastHB = !this.broadcastedHB;
+      this.broadcastedHB = true;
       this.y.db.requestTransaction(function*(){
         var ops = yield* this.getOperations(m.stateVector);
-        conn.broadcastedHB = true;
         if (ops.length > 0) {
-          conn.broadcast({
+          m = {
             type: "update",
             ops: ops
-          });
+          };
+          if (!broadcastHB) {
+            conn.send(sender, m);
+          } else {
+            // broadcast only once!
+            conn.broadcast(m);
+          }
         }
       });
     } else if (m.type === "sync done") {
       this.connections[sender].isSynced = true;
-      this.findNextSyncTarget();
+      if (sender === this.currentSyncTarget) {
+        this.currentSyncTarget = null;
+        this.findNextSyncTarget();
+      }
     } else if (m.type === "update") {
       if (this.forwardToSyncingClients) {
         for (var client of this.syncingClients) {
diff --git a/src/Connectors/Test.js b/src/Connectors/Test.js
index 5a41348e..9152e8ae 100644
--- a/src/Connectors/Test.js
+++ b/src/Connectors/Test.js
@@ -73,10 +73,26 @@ class Test extends AbstractConnector {
     }
   }
   flushAll () {
-    var c = true;
-    while (c) {
-      c = flushOne();
+    var def = Promise.defer();
+    // flushes may result in more created operations,
+    // flush until there is nothing more to flush
+    function nextFlush() {
+      var c = flushOne();
+      if (c) {
+        while(flushOne()) {
+          //nop
+        }
+        wait().then(nextFlush);
+      } else {
+        wait().then(function(){
+          def.resolve();
+        });
+      }
     }
+    // in the case that there are
+    // still actions that want to be performed
+    wait(0).then(nextFlush);
+    return def.promise;
   }
   flushOne() {
     flushOne();
diff --git a/src/Helper.spec.js b/src/Helper.spec.js
index d42a1aeb..560ec628 100644
--- a/src/Helper.spec.js
+++ b/src/Helper.spec.js
@@ -5,6 +5,13 @@
   This is "just" a compilation of functions that help to test this library!
 ***/
 
+function wait(t = 0) {//eslint-disable-line
+  var def = Promise.defer();
+  setTimeout(function(){
+    def.resolve();
+  }, t);
+  return def.promise;
+}
 
 // returns a random element of o
 // works on Object, and Array
@@ -26,7 +33,7 @@ function getRandomNumber(n) {//eslint-disable-line
   return Math.floor(Math.random() * n);
 }
 
-function applyRandomTransactions (users, objects, transactions, numberOfTransactions) {//eslint-disable-line
+async function applyRandomTransactions (users, objects, transactions, numberOfTransactions) {//eslint-disable-line
   function randomTransaction (root) {
     var f = getRandom(transactions);
     f(root);
@@ -39,40 +46,45 @@ function applyRandomTransactions (users, objects, transactions, numberOfTransact
     } else {
       randomTransaction(getRandom(objects));
     }
+    wait();
   }
 }
 
-function compareAllUsers(users){//eslint-disable-line
+async function compareAllUsers(users){//eslint-disable-line
   var s1, s2;
+  var db1 = [];
   function* t1(){
     s1 = yield* this.getStateSet();
   }
   function* t2(){
     s2 = yield* this.getStateSet();
   }
-  users[0].connector.flushAll();
-  for (var uid = 0; uid + 1 < users.length; uid++) {
-    var u1 = users[uid];
-    var u2 = users[uid + 1];
-    u1.db.requestTransaction(t1);
-    u2.db.requestTransaction(t2);
-    expect(s1).toEqual(s2);
-    var db1 = [];
-    var db2 = [];
-    u1.db.os.iterate(null, null, function(o){//eslint-disable-line
-      db1.push(o);
-    });
-    u2.db.os.iterate(null, null, function(o){//eslint-disable-line
-      db2.push(o);
-    });
-
-    for (var key in db1) {
-      expect(db1[key]).toEqual(db2[key]);
+  await users[0].connector.flushAll();
+  for (var uid = 0; uid < users.length; uid++) {
+    if (s1 == null) {
+      var u = users[uid];
+      u.db.requestTransaction(t1);
+      await wait();
+      u.db.os.iterate(null, null, function(o){//eslint-disable-line
+        db1.push(o);
+      });
+    } else {
+      var u2 = users[uid];
+      u2.db.requestTransaction(t2);
+      await wait();
+      expect(s1).toEqual(s2);
+      var count = 0;
+      u2.db.os.iterate(null, null, function(o){//eslint-disable-line
+        expect(db1[count++]).toEqual(o);
+      });
     }
   }
 }
 
-function createUsers(self, numberOfUsers, done) {//eslint-disable-line
+async function createUsers(self, numberOfUsers) {//eslint-disable-line
+  if (globalRoom.users[0] != null) {//eslint-disable-line
+    await globalRoom.users[0].flushAll();//eslint-disable-line
+  }
   //destroy old users
   for (var u in globalRoom.users) {//eslint-disable-line
     globalRoom.users[u].y.destroy()//eslint-disable-line
@@ -91,8 +103,5 @@ function createUsers(self, numberOfUsers, done) {//eslint-disable-line
       }
     }));
   }
-  Promise.all(promises).then( users => {
-    self.users = users;
-    done();
-  });
+  self.users = await Promise.all(promises);
 }
diff --git a/src/OperationStores/Memory.js b/src/OperationStores/Memory.js
index 2038848a..93c6546b 100644
--- a/src/OperationStores/Memory.js
+++ b/src/OperationStores/Memory.js
@@ -126,7 +126,7 @@ Y.Memory = (function(){ //eslint-disable-line no-unused-vars
     requestTransaction (_makeGen : Function) {
       if (!this.transactionInProgress) {
         this.transactionInProgress = true;
-        window.setTimeout(() => {
+        setTimeout(() => {
           var makeGen = _makeGen;
           while (makeGen != null) {
             var t = new Transaction(this);
diff --git a/src/Types/Array.spec.js b/src/Types/Array.spec.js
index 5c0d845e..b7cf1334 100644
--- a/src/Types/Array.spec.js
+++ b/src/Types/Array.spec.js
@@ -1,116 +1,98 @@
 /* @flow */
 /*eslint-env browser,jasmine */
 
-var numberOfYArrayTests = 20;
+var numberOfYArrayTests = 80;
 
 describe("Array Type", function(){
-  jasmine.DEFAULT_TIMEOUT_INTERVAL = 5000;
-  beforeEach(function(done){
-    createUsers(this, 5, done);
+  var y1, y2, y3, flushAll;
+
+  jasmine.DEFAULT_TIMEOUT_INTERVAL = 50000;
+  beforeEach(async function(done){
+    await createUsers(this, 5);
+    y1 = this.users[0].root;
+    y2 = this.users[1].root;
+    y3 = this.users[2].root;
+    flushAll = this.users[0].connector.flushAll;
+    done();
+  });
+  afterEach(async function(done) {
+    await compareAllUsers(this.users);
+    done();
   });
 
   describe("Basic tests", function(){
-    it("insert three elements", function(done){
-      var y = this.users[0].root;
-      y.set("Array", Y.Array).then(function(array) {
-        array.insert(0, [1, 2, 3]);
-        return y.get("Array");
-      }).then(function(array){
-        expect(array.toArray()).toEqual([1, 2, 3]);
-        done();
-      });
+    it("insert three elements, try re-get property", async function(done){
+      var array = await y1.set("Array", Y.Array);
+      array.insert(0, [1, 2, 3]);
+      array = await y1.get("Array"); // re-get property
+      expect(array.toArray()).toEqual([1, 2, 3]);
+      done();
     });
-    it("Basic insert in array (handle three conflicts)", function(done){
-      var y = this.users[0];
+    it("Basic insert in array (handle three conflicts)", async function(done){
       var l1, l2, l3;
-      y.root.set("Array", Y.Array).then((array)=>{
-        l1 = array;
-        y.connector.flushAll();
-        l1.insert(0, [0]);
-        return this.users[1].root.get("Array");
-      }).then((array)=>{
-        l2 = array;
-        l2.insert(0, [1]);
-        return this.users[2].root.get("Array");
-      }).then((array)=>{
-        l3 = array;
-        l3.insert(0, [2]);
-        y.connector.flushAll();
-        expect(l1.toArray()).toEqual(l2.toArray());
-        expect(l2.toArray()).toEqual(l3.toArray());
-        compareAllUsers(this.users);
-        done();
-      });
+      await y1.set("Array", Y.Array);
+      await flushAll();
+      (l1 = await y1.get("Array")).insert(0, [0]);
+      (l2 = await y2.get("Array")).insert(0, [1]);
+      (l3 = await y3.get("Array")).insert(0, [2]);
+      await flushAll();
+      expect(l1.toArray()).toEqual(l2.toArray());
+      expect(l2.toArray()).toEqual(l3.toArray());
+      done();
     });
-    it("Basic insert&delete in array (handle three conflicts)", function(done){
-      var y = this.users[0];
+    it("Basic insert&delete in array (handle three conflicts)", async function(done){
       var l1, l2, l3;
-      y.root.set("Array", Y.Array).then((array)=>{
-        l1 = array;
-        l1.insert(0, ["x", "y", "z"]);
-        y.connector.flushAll();
-        l1.insert(1, [0]);
-        return this.users[1].root.get("Array");
-      }).then((array)=>{
-        l2 = array;
-        l2.delete(0);
-        l2.delete(1);
-        return this.users[2].root.get("Array");
-      }).then((array)=>{
-        l3 = array;
-        l3.insert(1, [2]);
-        y.connector.flushAll();
-        expect(l1.toArray()).toEqual(l2.toArray());
-        expect(l2.toArray()).toEqual(l3.toArray());
-        expect(l2.toArray()).toEqual([0, 2, "y"]);
-        compareAllUsers(this.users);
-        done();
-      });
+      l1 = await y1.set("Array", Y.Array);
+      l1.insert(0, ["x", "y", "z"]);
+      await flushAll();
+      l1.insert(1, [0]);
+      l2 = await y2.get("Array");
+      l2.delete(0);
+      l2.delete(1);
+      l3 = await y3.get("Array");
+      l3.insert(1, [2]);
+      await flushAll();
+      expect(l1.toArray()).toEqual(l2.toArray());
+      expect(l2.toArray()).toEqual(l3.toArray());
+      expect(l2.toArray()).toEqual([0, 2, "y"]);
+      done();
     });
-    it("Basic insert. Then delete the whole array", function(done){
-      var y = this.users[0];
+    it("Basic insert. Then delete the whole array", async function(done){
       var l1, l2, l3;
-      y.root.set("Array", Y.Array).then((array)=>{
-        l1 = array;
-        l1.insert(0, ["x", "y", "z"]);
-        y.connector.flushAll();
-        l1.delete(0, 3);
-        return this.users[1].root.get("Array");
-      }).then((array)=>{
-        l2 = array;
-        return this.users[2].root.get("Array");
-      }).then((array)=>{
-        l3 = array;
-        y.connector.flushAll();
-        expect(l1.toArray()).toEqual(l2.toArray());
-        expect(l2.toArray()).toEqual(l3.toArray());
-        expect(l2.toArray()).toEqual([]);
-        compareAllUsers(this.users);
-        done();
-      });
+      l1 = await y1.set("Array", Y.Array);
+      l1.insert(0, ["x", "y", "z"]);
+      await flushAll();
+      l1.delete(0, 3);
+      l2 = await y2.get("Array");
+      l3 = await y3.get("Array");
+      await flushAll();
+      expect(l1.toArray()).toEqual(l2.toArray());
+      expect(l2.toArray()).toEqual(l3.toArray());
+      expect(l2.toArray()).toEqual([]);
+      done();
     });
-    it("throw insert & delete events", function(done){
-      this.users[0].root.set("array", Y.Array).then(function(array){
-        var event;
-        array.observe(function(e){
-          event = e;
-        });
-        array.insert(0, [0]);
-        expect(event).toEqual([{
-          type: "insert",
-          object: array,
-          index: 0,
-          length: 1
-        }]);
-        array.delete(0);
-        expect(event).toEqual([{
-          type: "delete",
-          object: array,
-          index: 0,
-          length: 1
-        }]);
-        done();
+    it("throw insert & delete events", async function(done){
+      var array = await this.users[0].root.set("array", Y.Array);
+      var event;
+      array.observe(function(e){
+        event = e;
       });
+      array.insert(0, [0]);
+      expect(event).toEqual([{
+        type: "insert",
+        object: array,
+        index: 0,
+        length: 1
+      }]);
+      array.delete(0);
+      expect(event).toEqual([{
+        type: "delete",
+        object: array,
+        index: 0,
+        length: 1
+      }]);
+      await wait(50);
+      done();
     });
   });
   describe(`${numberOfYArrayTests} Random tests`, function(){
@@ -136,34 +118,26 @@ describe("Array Type", function(){
         }
       }
     }
-    beforeEach(function(done){
-      this.users[0].root.set("Array", Y.Array);
-      this.users[0].connector.flushAll();
+    beforeEach(async function(done){
+      await this.users[0].root.set("Array", Y.Array);
+      await flushAll();
 
-      var then = Promise.resolve();
-      var arrays = [];
-      for (var u of this.users) {
-        then = then.then(function(){ //eslint-disable-line
-          return u.root.get("Array");
-        }).then(function(array){//eslint-disable-line
-          arrays.push(array);
-        });
+      var promises = [];
+      for (var u = 0; u < this.users.length; u++) {
+        promises.push(this.users[u].root.get("Array"));
       }
-      this.arrays = arrays;
-      then.then(function(){
-        done();
-      });
+      this.arrays = await Promise.all(promises);
+      done();
     });
-    it("arrays.length equals users.length", function(){
+    it("arrays.length equals users.length", async function(done){
       expect(this.arrays.length).toEqual(this.users.length);
+      done();
     });
-    it(`succeed after ${numberOfYArrayTests} actions`, function(done){
-      applyRandomTransactions(this.users, this.arrays, randomArrayTransactions, numberOfYArrayTests);
-      setTimeout(()=>{
-        compareAllUsers(this.users);
-        compareArrayValues(this.arrays);
-        done();
-      }, 500);
+    it(`succeed after ${numberOfYArrayTests} actions`, async function(done){
+      await applyRandomTransactions(this.users, this.arrays, randomArrayTransactions, numberOfYArrayTests);
+      await flushAll();
+      await compareArrayValues(this.arrays);
+      done();
     });
   });
 });