diff --git a/src/combinedeventstreamtest/ChangeA.java b/src/combinedeventstreamtest/ChangeA.java
new file mode 100644
index 0000000..f765cbe
--- /dev/null
+++ b/src/combinedeventstreamtest/ChangeA.java
@@ -0,0 +1,47 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package combinedeventstreamtest;
+
+import java.util.Optional;
+import org.reactfx.Change;
+
+/**
+ *
+ * @author bwhitworth
+ */
+public class ChangeA extends ChangeBase<Double> {
+
+   public ChangeA(DataModel model, double oldVal, double newVal) {
+      super(model, oldVal, newVal);
+   }
+   
+   public ChangeA(DataModel model, Change<Number> c) {      
+      super(model, (Double)c.getOldValue(), (Double)c.getNewValue());
+   }
+   
+   @Override
+   public ChangeBase<Double> invert() {
+      System.out.println("ChangeA invert "+this);
+      return new ChangeA(this.model, this.newValue, this.oldValue);
+   }
+
+   @Override
+   public void redo() {
+      System.out.println("ChangeA redo "+this);
+      this.model.setA(this.newValue);
+   }
+
+   @Override
+   public Optional<UndoChange> mergeWith(UndoChange other) {
+      System.out.print("ChangeA attempting merge with "+other+"... ");
+      if(other instanceof ChangeA) {
+         System.out.println("merged");
+         return Optional.of(new ChangeA(this.model, this.oldValue, ((ChangeA) other).newValue));
+      }
+      System.out.println("did not merge");
+      return Optional.empty();
+   }      
+}
diff --git a/src/combinedeventstreamtest/ChangeB.java b/src/combinedeventstreamtest/ChangeB.java
new file mode 100644
index 0000000..fe6546f
--- /dev/null
+++ b/src/combinedeventstreamtest/ChangeB.java
@@ -0,0 +1,48 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package combinedeventstreamtest;
+
+import java.util.Optional;
+import org.reactfx.Change;
+
+/**
+ *
+ * @author bwhitworth
+ */
+public class ChangeB extends ChangeBase<Double> {
+
+   public ChangeB(DataModel model, double oldVal, double newVal) {
+      super(model, oldVal, newVal);
+   }
+   
+   public ChangeB(DataModel model, Change<Number> c) {      
+      super(model, (Double)c.getOldValue(), (Double)c.getNewValue());
+   }
+   
+   @Override
+   public ChangeBase<Double> invert() {
+      System.out.println("ChangeB invert "+this);
+      return new ChangeB(this.model, this.newValue, this.oldValue);
+   }
+
+   @Override
+   public void redo() {
+      System.out.println("ChangeB redo "+this);
+      this.model.setB(this.newValue);
+   }
+
+   @Override
+   public Optional<UndoChange> mergeWith(UndoChange other) {
+      System.out.print("ChangeB attempting merge with "+other+"... ");
+      if(other instanceof ChangeB) {
+         System.out.println("merged");
+         return Optional.of(new ChangeB(this.model, this.oldValue, ((ChangeB) other).newValue));
+      }
+      System.out.println("did not merge");
+      return Optional.empty();
+   }      
+   
+}
diff --git a/src/combinedeventstreamtest/ChangeBase.java b/src/combinedeventstreamtest/ChangeBase.java
new file mode 100644
index 0000000..7dac775
--- /dev/null
+++ b/src/combinedeventstreamtest/ChangeBase.java
@@ -0,0 +1,61 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package combinedeventstreamtest;
+
+import java.util.Objects;
+import java.util.Optional;
+
+/**
+ *
+ * @author bwhitworth
+ */
+public abstract class ChangeBase<T> implements UndoChange {
+   protected final T oldValue, newValue;
+   protected final DataModel model;
+   
+   protected ChangeBase(DataModel model, T oldValue, T newValue) {
+      this.model = model;
+      this.oldValue = oldValue;
+      this.newValue = newValue;
+   }
+   
+   public abstract ChangeBase<T> invert();
+   public abstract void redo();
+   
+   public Optional<ChangeBase<?>> mergeWith(ChangeBase<?> other) {
+      return Optional.empty();
+   }
+
+   @Override
+   public int hashCode() {
+      return Objects.hash(this.oldValue, this.newValue);
+   }      
+
+   @Override
+   public boolean equals(Object obj) {
+      if (this == obj) {
+         return true;
+      }
+      if (obj == null) {
+         return false;
+      }
+      if (getClass() != obj.getClass()) {
+         return false;
+      }
+      final ChangeBase<?> other = (ChangeBase<?>) obj;
+      if (!Objects.equals(this.oldValue, other.oldValue)) {
+         return false;
+      }
+      if (!Objects.equals(this.newValue, other.newValue)) {
+         return false;
+      }
+      if (!Objects.equals(this.model, other.model)) {
+         return false;
+      }
+      return true;
+   }
+
+}
diff --git a/src/combinedeventstreamtest/ChangeBoth.java b/src/combinedeventstreamtest/ChangeBoth.java
new file mode 100644
index 0000000..9aecc13
--- /dev/null
+++ b/src/combinedeventstreamtest/ChangeBoth.java
@@ -0,0 +1,93 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package combinedeventstreamtest;
+
+import java.util.Objects;
+import java.util.Optional;
+import org.reactfx.util.Tuple2;
+
+/**
+ *
+ * @author bwhitworth
+ */
+public class ChangeBoth implements UndoChange {
+
+   private final ChangeA aChange;
+   private final ChangeB bChange;
+   
+   public ChangeBoth(ChangeA ac, ChangeB bc) {
+      this.aChange = ac;
+      this.bChange = bc;
+   }
+   
+   public ChangeBoth(Tuple2<UndoChange, UndoChange> tuple) {
+      this.aChange = ((ChangeBoth)tuple.get1()).aChange;
+      this.bChange = ((ChangeBoth)tuple.get2()).bChange;
+   }
+   
+   @Override
+   public UndoChange invert() {
+      System.out.println("ChangeBoth invert "+this);
+      return new ChangeBoth(new ChangeA(this.aChange.model, this.aChange.newValue, this.aChange.oldValue), 
+                            new ChangeB(this.bChange.model, this.bChange.newValue, this.bChange.oldValue));
+   }
+
+   @Override
+   public void redo() {
+      System.out.println("ChangeBoth redo "+this);
+      DataModel model = this.aChange.model;
+      model.setA(this.aChange.newValue);
+      model.setB(this.bChange.newValue);
+   }
+
+   @Override
+   public Optional<UndoChange> mergeWith(UndoChange other) {
+      System.out.print("ChangeBoth attempting merge with "+other+"... ");
+      if(other instanceof ChangeBoth) {
+         System.out.println("merged");
+         ChangeBoth cb = (ChangeBoth)other;
+         ChangeA ac = (cb.aChange == null) ? this.aChange : cb.aChange;
+         ChangeB bc = (cb.bChange == null) ? this.bChange : cb.bChange;
+         return Optional.of(
+                 new ChangeBoth(
+                         new ChangeA(this.aChange.model, this.aChange.oldValue, ac.newValue),
+                         new ChangeB(this.bChange.model, this.bChange.oldValue, bc.newValue)
+                 )
+         );
+      }
+      System.out.println("did not merge");
+      return Optional.empty();
+   }   
+
+   @Override
+   public int hashCode() {
+      int hash = 7;
+      hash = 17 * hash + Objects.hashCode(this.aChange);
+      hash = 17 * hash + Objects.hashCode(this.bChange);
+      return hash;
+   }
+
+   @Override
+   public boolean equals(Object obj) {
+      if (this == obj) {
+         return true;
+      }
+      if (obj == null) {
+         return false;
+      }
+      if (getClass() != obj.getClass()) {
+         return false;
+      }
+      final ChangeBoth other = (ChangeBoth) obj;
+      if (!Objects.equals(this.aChange, other.aChange)) {
+         return false;
+      }
+      if (!Objects.equals(this.bChange, other.bChange)) {
+         return false;
+      }
+      return true;
+   }   
+}
diff --git a/src/combinedeventstreamtest/CombinedEventStreamTest.java b/src/combinedeventstreamtest/CombinedEventStreamTest.java
new file mode 100644
index 0000000..d9d6352
--- /dev/null
+++ b/src/combinedeventstreamtest/CombinedEventStreamTest.java
@@ -0,0 +1,118 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package combinedeventstreamtest;
+
+import javafx.application.Application;
+import javafx.beans.property.DoubleProperty;
+import javafx.collections.FXCollections;
+import javafx.collections.ListChangeListener;
+import javafx.collections.ObservableList;
+import javafx.event.ActionEvent;
+import javafx.scene.Scene;
+import javafx.scene.control.Button;
+import javafx.scene.layout.FlowPane;
+import javafx.stage.Stage;
+import org.fxmisc.undo.UndoManager;
+import org.fxmisc.undo.UndoManagerFactory;
+import org.reactfx.Change;
+import org.reactfx.EventStream;
+import org.reactfx.EventStreams;
+
+/**
+ *
+ * @author bwhitworth
+ */
+public class CombinedEventStreamTest extends Application {
+   
+   @Override
+   public void start(Stage primaryStage) {
+      //a data model
+      DataModel model = new DataModel();
+      //event streams of property changes
+      EventStream<UndoChange> changeAStream = EventStreams.changesOf(model.aProperty())
+              .hook(c -> System.out.println("Change in A stream"))
+              .map(c -> new ChangeA(model, (Change<Number>)c));
+      EventStream<UndoChange> changeBStream = EventStreams.changesOf(model.bProperty())
+              .hook(c -> System.out.println("Change in B stream"))
+              .map(c -> new ChangeB(model, (Change<Number>)c));
+      //combine event streams
+      EventStream<UndoChange> bothStream = EventStreams.merge(changeAStream, changeBStream);    
+      
+//      EventStream<UndoChange> bothStream = EventStreams.combine(changeAStream, changeBStream)
+//              .hook(c -> System.out.println("Change in Both stream"))
+//              .map(ChangeBoth::new);   
+      
+      //undo manager
+      UndoManager<UndoChange> um = UndoManagerFactory.unlimitedHistoryUndoManager(
+              bothStream, 
+              c -> c.invert(), 
+              c -> c.redo(),
+              (c1, c2) -> c1.mergeWith(c2)
+      );
+
+      //generate new A
+      Button aButton = new Button();
+      aButton.setText("A change");
+      aButton.setOnAction((ActionEvent event) -> {
+         System.out.print(model+"\t->\t");
+         model.setA(Math.random()*10.0);
+         System.out.println(model);
+      });
+      
+      //generate new B
+      Button bButton = new Button();
+      bButton.setText("B change");
+      bButton.setOnAction((ActionEvent event) -> {
+         System.out.print(model+"\t->\t");
+         model.setB(Math.random()*10.0);
+         System.out.println(model);
+      });
+      
+      //generate new A and B
+      Button bothButton = new Button("A and B change");
+      bothButton.setOnAction(event -> {
+         System.out.print(model+"\t->\t");
+         model.setA(Math.random()*10.0);
+         model.setB(Math.random()*10.0);
+         System.out.println(model);         
+      });
+
+      //undo/redo buttons
+      Button undoButton = new Button("Undo");
+      Button redoButton = new Button("Redo");
+      undoButton.disableProperty().bind(um.undoAvailableProperty().map(x -> !x));
+      redoButton.disableProperty().bind(um.redoAvailableProperty().map(x -> !x));
+      undoButton.setOnAction(event -> {
+         System.out.print("undo "+model+"\t->\t");         
+         um.undo();
+         System.out.println(model);
+      });
+      redoButton.setOnAction(event -> {
+         System.out.print("redo "+model+"\t->\t");                  
+         um.redo();
+         System.out.println(model);
+      });
+      
+      FlowPane root = new FlowPane();
+      root.setHgap(5);
+      root.setVgap(5);
+      root.getChildren().addAll(aButton, bButton, bothButton, undoButton, redoButton);
+      
+      Scene scene = new Scene(root, 300, 250);
+      
+      primaryStage.setTitle("Combined stream test");
+      primaryStage.setScene(scene);
+      primaryStage.show();
+   }
+
+   /**
+    * @param args the command line arguments
+    */
+   public static void main(String[] args) {
+      launch(args);
+   }
+   
+}
diff --git a/src/combinedeventstreamtest/DataModel.java b/src/combinedeventstreamtest/DataModel.java
new file mode 100644
index 0000000..2d45069
--- /dev/null
+++ b/src/combinedeventstreamtest/DataModel.java
@@ -0,0 +1,74 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package combinedeventstreamtest;
+
+import java.util.Objects;
+import javafx.beans.property.DoubleProperty;
+import javafx.beans.property.SimpleDoubleProperty;
+
+/**
+ *
+ * @author bwhitworth
+ */
+public class DataModel {
+   private DoubleProperty a, b;
+   
+   public DataModel() {
+      this.a = new SimpleDoubleProperty();
+      this.b = new SimpleDoubleProperty();
+   }
+   
+   public DoubleProperty aProperty() {
+      return this.a;
+   }
+   
+   public DoubleProperty bProperty() {
+      return this.b;
+   }
+   
+   public void setA(double a) {
+      this.a.set(a);
+   }
+   
+   public void setB(double b) {
+      this.b.set(b);
+   }
+
+   @Override
+   public String toString() {
+      return this.a.doubleValue()+"\t"+this.b.doubleValue();
+   }
+
+   @Override
+   public int hashCode() {
+      int hash = 7;
+      hash = 67 * hash + Objects.hashCode(this.a);
+      hash = 67 * hash + Objects.hashCode(this.b);
+      return hash;
+   }
+
+   @Override
+   public boolean equals(Object obj) {
+      if (this == obj) {
+         return true;
+      }
+      if (obj == null) {
+         return false;
+      }
+      if (getClass() != obj.getClass()) {
+         return false;
+      }
+      final DataModel other = (DataModel) obj;
+      if (!Objects.equals(this.a, other.a)) {
+         return false;
+      }
+      if (!Objects.equals(this.b, other.b)) {
+         return false;
+      }
+      return true;
+   }
+
+}
diff --git a/src/combinedeventstreamtest/UndoChange.java b/src/combinedeventstreamtest/UndoChange.java
new file mode 100644
index 0000000..dab4cfe
--- /dev/null
+++ b/src/combinedeventstreamtest/UndoChange.java
@@ -0,0 +1,19 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package combinedeventstreamtest;
+
+import java.util.Optional;
+
+/**
+ *
+ * @author bwhitworth
+ */
+public interface UndoChange {
+   public void redo();
+   public UndoChange invert();
+   public Optional<UndoChange> mergeWith(UndoChange other);
+   
+}