Introduce basic unit test for AutowiredAnnotationBeanPostProcessor.processInjection()

spring-beans/src/test/java/org/springframework/beans/factory/annotation/AutowiredAnnotationBeanPostProcessorTests.java

@@ -118,6 +118,20 @@ class AutowiredAnnotationBeanPostProcessorTests {
 				.withRootCauseInstanceOf(IllegalStateException.class);
 	}
 
+	@Test
+	void processInjection() {
+		ResourceInjectionBean bean = new ResourceInjectionBean();
+		assertThat(bean.getTestBean()).isNull();
+		assertThat(bean.getTestBean2()).isNull();
+
+		TestBean tb = new TestBean();
+		bf.registerSingleton("testBean", tb);
+		bpp.processInjection(bean);
+
+		assertThat(bean.getTestBean()).isSameAs(tb);
+		assertThat(bean.getTestBean2()).isSameAs(tb);
+	}
+
 	@Test
 	void resourceInjection() {
 		RootBeanDefinition bd = new RootBeanDefinition(ResourceInjectionBean.class);