Improve exception message if unable to select a bean to wrap for @MockitoSpyBean

See spring-projectsGH-33935

Author: quaff

spring-test/src/main/java/org/springframework/test/context/bean/override/BeanOverrideBeanFactoryPostProcessor.java

@@ -242,6 +242,9 @@ private void wrapBean(ConfigurableListableBeanFactory beanFactory, BeanOverrideH
 					if (candidateCount == 0) {
 						message += "there are no beans of type %s (as required by field '%s.%s')."
 								.formatted(beanType, field.getDeclaringClass().getSimpleName(), field.getName());
+						message += " If the bean is defined from a @Bean method,"
+								+ " please make sure the return type is the most specific type (recommended) or type can be assigned to %s."
+								.formatted(beanType);
 					}
 					else {
 						message += "found %d beans of type %s (as required by field '%s.%s'): %s"

spring-test/src/test/java/org/springframework/test/context/bean/override/mockito/MockitoSpyBeanConfigurationErrorTests.java

@@ -50,7 +50,7 @@ void contextCustomizerCannotBeCreatedWithNoSuchBeanType() {
 		BeanOverrideContextCustomizerTestUtils.customizeApplicationContext(ByTypeSingleLookup.class, context);
 		assertThatIllegalStateException()
 				.isThrownBy(context::refresh)
-				.withMessage("""
+				.withMessageStartingWith("""
 						Unable to select a bean to wrap: there are no beans of type java.lang.String \
 						(as required by field 'ByTypeSingleLookup.example').""");
 	}