Avoid returning null from TestContext.getTestClass()

Our mock didn't configure an expectation so null was returned. That's
prohibited by the javadoc and some recent Framework changes mean that
it's no longer tolerated.

spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/SpringBootDependencyInjectionTestExecutionListenerTests.java

@@ -53,8 +53,10 @@ class SpringBootDependencyInjectionTestExecutionListenerTests {
 	}
 
 	@Test
+	@SuppressWarnings("unchecked")
 	void prepareFailingTestInstanceShouldPrintReport(CapturedOutput output) throws Exception {
 		TestContext testContext = mock(TestContext.class);
+		given(testContext.getTestClass()).willReturn((Class) Config.class);
 		given(testContext.getTestInstance()).willThrow(new IllegalStateException());
 		SpringApplication application = new SpringApplication(Config.class);
 		application.setWebApplicationType(WebApplicationType.NONE);
@@ -71,8 +73,10 @@ class SpringBootDependencyInjectionTestExecutionListenerTests {
 	}
 
 	@Test
+	@SuppressWarnings("unchecked")
 	void originalFailureIsThrownWhenReportGenerationFails() {
 		TestContext testContext = mock(TestContext.class);
+		given(testContext.getTestClass()).willReturn((Class) Config.class);
 		IllegalStateException originalFailure = new IllegalStateException();
 		given(testContext.getTestInstance()).willThrow(originalFailure);
 		SpringApplication application = new SpringApplication(Config.class);