Add tests to DelegatingWebReactiveConfigurationTests

spring-web-reactive/src/main/java/org/springframework/web/reactive/config/WebReactiveConfigurerComposite.java

@@ -139,7 +139,7 @@ public class WebReactiveConfigurerComposite implements WebReactiveConfigurer {
 			return Optional.empty();
 		}
 		else if (result.size() == 1) {
-			return result.get(1);
+			return result.get(0);
 		}
 		else {
 			throw new IllegalStateException("More than one WebReactiveConfigurer implements " +

spring-web-reactive/src/test/java/org/springframework/web/reactive/config/DelegatingWebReactiveConfigurationTests.java

@@ -16,12 +16,15 @@
 
 package org.springframework.web.reactive.config;
 
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 
 import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.mockito.ArgumentCaptor;
 import org.mockito.Captor;
 import org.mockito.Mock;
@@ -36,6 +39,7 @@ import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
 import org.springframework.web.bind.support.ConfigurableWebBindingInitializer;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolverBuilder;
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter;
+import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerMapping;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertSame;
@@ -43,7 +47,9 @@ import static org.junit.Assert.assertTrue;
 import static org.mockito.BDDMockito.given;
 import static org.mockito.Matchers.any;
 import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
 
 /**
  * Test fixture for {@link DelegatingWebReactiveConfiguration} tests.
@@ -66,6 +72,9 @@ public class DelegatingWebReactiveConfigurationTests {
 	@Captor
 	private ArgumentCaptor<FormatterRegistry> formatterRegistry;
 
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
 
 	@Before
 	public void setUp() {
@@ -78,6 +87,52 @@ public class DelegatingWebReactiveConfigurationTests {
 		given(webReactiveConfigurer.getMessageCodesResolver()).willReturn(Optional.empty());
 	}
 
+
+	@Test
+	public void requestMappingHandlerMapping() throws Exception {
+		delegatingConfig.setConfigurers(Collections.singletonList(webReactiveConfigurer));
+		delegatingConfig.requestMappingHandlerMapping();
+
+		verify(webReactiveConfigurer).createRequestMappingHandlerMapping();
+		verify(webReactiveConfigurer).configureRequestedContentTypeResolver(any(RequestedContentTypeResolverBuilder.class));
+		verify(webReactiveConfigurer).addCorsMappings(any(CorsRegistry.class));
+		verify(webReactiveConfigurer).configurePathMatching(any(PathMatchConfigurer.class));
+	}
+
+	@Test
+	public void requestMappingHandlerMappingFactoryMethod() throws Exception {
+		RequestMappingHandlerMapping mapping = new RequestMappingHandlerMapping();
+
+		WebReactiveConfigurer configurer1 = mock(WebReactiveConfigurer.class);
+		WebReactiveConfigurer configurer2 = mock(WebReactiveConfigurer.class);
+
+		when(configurer1.createRequestMappingHandlerMapping()).thenReturn(Optional.of(mapping));
+		when(configurer2.createRequestMappingHandlerMapping()).thenReturn(Optional.empty());
+
+		delegatingConfig.setConfigurers(Arrays.asList(configurer1, configurer2));
+		Object actual = delegatingConfig.createRequestMappingHandlerMapping();
+
+		assertSame(mapping, actual);
+	}
+
+	@Test
+	public void multipleRequestMappingHandlerMappingFactoryMethods() throws Exception {
+		RequestMappingHandlerMapping mapping1 = new RequestMappingHandlerMapping();
+		RequestMappingHandlerMapping mapping2 = new RequestMappingHandlerMapping();
+
+		WebReactiveConfigurer configurer1 = mock(WebReactiveConfigurer.class);
+		WebReactiveConfigurer configurer2 = mock(WebReactiveConfigurer.class);
+
+		when(configurer1.createRequestMappingHandlerMapping()).thenReturn(Optional.of(mapping1));
+		when(configurer2.createRequestMappingHandlerMapping()).thenReturn(Optional.of(mapping2));
+
+		this.thrown.expectMessage("More than one WebReactiveConfigurer implements " +
+				"RequestMappingHandlerMapping factory method.");
+
+		delegatingConfig.setConfigurers(Arrays.asList(configurer1, configurer2));
+		delegatingConfig.createRequestMappingHandlerMapping();
+	}
+
 	@Test
 	public void requestMappingHandlerAdapter() throws Exception {
 		delegatingConfig.setConfigurers(Collections.singletonList(webReactiveConfigurer));
@@ -99,17 +154,6 @@ public class DelegatingWebReactiveConfigurationTests {
 		assertEquals(5, readers.getValue().size());
 	}
 
-	@Test
-	public void requestMappingHandlerMapping() throws Exception {
-		delegatingConfig.setConfigurers(Collections.singletonList(webReactiveConfigurer));
-		delegatingConfig.requestMappingHandlerMapping();
-
-		verify(webReactiveConfigurer).createRequestMappingHandlerMapping();
-		verify(webReactiveConfigurer).configureRequestedContentTypeResolver(any(RequestedContentTypeResolverBuilder.class));
-		verify(webReactiveConfigurer).addCorsMappings(any(CorsRegistry.class));
-		verify(webReactiveConfigurer).configurePathMatching(any(PathMatchConfigurer.class));
-	}
-
 	@Test
 	public void resourceHandlerMapping() throws Exception {
 		delegatingConfig.setConfigurers(Collections.singletonList(webReactiveConfigurer));
@@ -141,4 +185,5 @@ public class DelegatingWebReactiveConfigurationTests {
 
 		verify(webReactiveConfigurer).configureViewResolvers(any(ViewResolverRegistry.class));
 	}
+
 }