Use and wait for a latch to check that the interceptor is called

Spring MVC drives the postHandle method on any interceptors after the
response has been sent to the client. This meant that there was a
race between the test receiving the response and asserting that the
interceptor had been driven and Spring MVC driving the interceptor.

This commit updates the interceptor to use a CountDownLatch to track
whether or not it's been called. The test now waits for up to 30
seconds for the latch to be decremented.

Closes gh-1997

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/autoconfigure/EndpointMvcIntegrationTests.java

@@ -23,7 +23,8 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 import java.util.Collections;
 import java.util.Map;
-import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
 
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -58,7 +59,6 @@ import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.servlet.ModelAndView;
 import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
 
-import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
 
@@ -81,12 +81,12 @@ public class EndpointMvcIntegrationTests {
 	private TestInterceptor interceptor;
 
 	@Test
-	public void envEndpointNotHidden() {
+	public void envEndpointNotHidden() throws InterruptedException {
 		String body = new TestRestTemplate().getForObject("http://localhost:" + this.port
 				+ "/env/user.dir", String.class);
 		assertNotNull(body);
 		assertTrue("Wrong body: \n" + body, body.contains("spring-boot-actuator"));
-		assertEquals(1, this.interceptor.getCount());
+		assertTrue(this.interceptor.invoked());
 	}
 
 	@Target(ElementType.TYPE)
@@ -141,16 +141,16 @@ public class EndpointMvcIntegrationTests {
 
 	protected static class TestInterceptor extends HandlerInterceptorAdapter {
 
-		private final AtomicInteger count = new AtomicInteger(0);
+		private final CountDownLatch latch = new CountDownLatch(1);
 
 		@Override
 		public void postHandle(HttpServletRequest request, HttpServletResponse response,
 				Object handler, ModelAndView modelAndView) throws Exception {
-			this.count.incrementAndGet();
+			this.latch.countDown();
 		}
 
-		public int getCount() {
-			return this.count.get();
+		public boolean invoked() throws InterruptedException {
+			return this.latch.await(30, TimeUnit.SECONDS);
 		}
 
 	}