@@ -0,0 +1,692 @@
+package org.realityforge.arez;%0A%0Aimport java.util.ArrayList;%0Aimport javax.annotation.Nonnull;%0Aimport static org.testng.Assert.*;%0A%0Afinal class TestReaction%0A  implements Reaction%0A%7B%0A  private final ArrayList%3CObserver%3E _observers = new ArrayList%3C%3E();%0A%0A  @Override%0A  public void react( @Nonnull final Observer observer )%0A    throws Exception%0A  %7B%0A    observer.getDependencies().forEach( Observable::reportObserved );%0A    _observers.add( observer );%0A  %7D%0A%0A  void assertObserver( final int index, @Nonnull final Observer observer )%0A  %7B%0A    assertTrue( _observers.size() %3E index );%0A    assertEquals( _observers.get( index ), observer );%0A  %7D%0A%0A  int getCallCount()%0A  %7B%0A    return _observers.size();%0A  %7D%0A%7D%0A

Add reaction useful during testing