Add test for inaccessible configuration class

See gh-948

spring-boot/src/test/java/org/springframework/boot/SpringApplicationTests.java

@@ -110,6 +110,13 @@ public class SpringApplicationTests {
 		new SpringApplication().run();
 	}
 
+	@Test
+	public void sourcesMustBeAccessible() throws Exception {
+		this.thrown.expect(IllegalStateException.class);
+		this.thrown.expectMessage("Cannot load configuration");
+		new SpringApplication(InaccessibleConfiguration.class).run();
+	}
+
 	@Test
 	public void disableBanner() throws Exception {
 		SpringApplication application = spy(new SpringApplication(ExampleConfig.class));
@@ -269,7 +276,7 @@ public class SpringApplicationTests {
 	}
 
 	@Test
-	public void proprtiesFileEnhancesEnvironment() throws Exception {
+	public void propertiesFileEnhancesEnvironment() throws Exception {
 		SpringApplication application = new SpringApplication(ExampleConfig.class);
 		application.setWebEnvironment(false);
 		ConfigurableEnvironment environment = new StandardEnvironment();
@@ -468,6 +475,14 @@ public class SpringApplicationTests {
 		return false;
 	}
 
+	@Configuration
+	protected static class InaccessibleConfiguration {
+
+		private InaccessibleConfiguration() {
+		}
+
+	}
+
 	public static class SpyApplicationContext extends AnnotationConfigApplicationContext {
 
 		ConfigurableApplicationContext applicationContext = spy(new AnnotationConfigApplicationContext());