add test case for InjectorFactory usage

added startup exception when multiple InjectorFactory definitions are provided

pom.xml

@@ -44,6 +44,12 @@
 			<version>4.11</version>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.mockito</groupId>
+			<artifactId>mockito-core</artifactId>
+			<version>1.10.8</version>
+			<scope>test</scope>
+		</dependency>
 	</dependencies>
 
 	<properties>

src/main/java/org/springframework/guice/annotation/ModuleRegistryConfiguration.java

@@ -16,6 +16,7 @@ package org.springframework.guice.annotation;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
+import java.util.Map;
 import java.util.Map.Entry;
 
 import org.springframework.beans.BeansException;
@@ -28,6 +29,7 @@ import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
+import org.springframework.context.ApplicationContextException;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
@@ -96,7 +98,16 @@ public class ModuleRegistryConfiguration implements BeanDefinitionRegistryPostPr
         modules.add(new SpringModule(this.applicationContext));
         Injector injector = null;
         try {
-            injector = ((DefaultListableBeanFactory) registry).getBean(InjectorFactory.class).createInjector(modules);
+            Map<String, InjectorFactory> beansOfType = ((DefaultListableBeanFactory) registry).getBeansOfType(InjectorFactory.class);
+            if (beansOfType.size() > 1) {
+                throw new ApplicationContextException("Found multiple beans of type " + InjectorFactory.class.getName()
+                        + "  Please ensure that only one InjectorFactory bean is defined. InjectorFactory beans found: "
+                        + beansOfType.keySet());
+            }
+            else if(beansOfType.size() == 1) {
+                 InjectorFactory injectorFactory = beansOfType.values().iterator().next();
+                 injector = injectorFactory.createInjector(modules);
+            }
         } catch (NoSuchBeanDefinitionException e) {
             
         }

src/test/java/org/springframework/guice/InjectorFactoryTests.java

@@ -0,0 +1,50 @@
+package org.springframework.guice;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mockito;
+import org.springframework.context.ApplicationContextException;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.guice.annotation.ModuleRegistryConfiguration;
+import org.springframework.guice.injector.InjectorFactory;
+
+import com.google.inject.Guice;
+
+public class InjectorFactoryTests  {
+    
+    static final private InjectorFactory injectorFactory = Mockito.mock(InjectorFactory.class);
+    
+    @Before
+    public void init() {
+        Mockito.when(injectorFactory.createInjector(Mockito.anyList())).thenReturn(Guice.createInjector());
+    }
+    
+    @Test
+    public void testCustomInjectorIsCreated() {
+        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(InjectorFactoryConfig.class, ModuleRegistryConfiguration.class);
+        Mockito.verify(injectorFactory, Mockito.times(1)).createInjector(Mockito.anyList());
+    }
+    
+    @Test(expected=ApplicationContextException.class)
+    public void testMultipleInjectorFactoriesThrowsApplicationContextException() {
+        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(InjectorFactoryConfig.class, SecondInjectorFactoryConfig.class, ModuleRegistryConfiguration.class); 
+    }
+    
+    @Configuration
+    static class InjectorFactoryConfig {
+        @Bean
+        public InjectorFactory injectorFactory() { 
+           return injectorFactory;
+        }
+    }
+    
+    @Configuration
+    static class SecondInjectorFactoryConfig {
+        @Bean
+        public InjectorFactory injectorFactory2() { 
+            return injectorFactory;
+        }
+    }
+}