Reduce flakiness of LayoutIntegrationTests

Two of the tests were waiting for log output using a one-off call to
Thread.sleep(). In addition to being brittle, the tests would fail with
an NPE (while trying to assert on the "timestamp" field) that doesn't
point to the cause of the failure directly.

Also removed the redundant assertThat(jsonNode).isNotNull() as
objectMapper.readTree() will never return null in Jackson 2.10.x, see
FasterXML/jackson-databind#2211

Author: cleiner

dropwizard-json-logging/pom.xml

@@ -116,6 +116,11 @@
             <artifactId>dropwizard-configuration</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.awaitility</groupId>
+            <artifactId>awaitility</artifactId>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
 </project>

dropwizard-json-logging/src/test/java/io/dropwizard/logging/json/LayoutIntegrationTests.java

@@ -37,6 +37,7 @@
 import static java.util.Objects.requireNonNull;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.entry;
+import static org.awaitility.Awaitility.await;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
@@ -149,10 +150,10 @@ public void testLogJsonToConsole() throws Exception {
             defaultLoggingFactory.configure(new MetricRegistry(), "json-log-test");
             Marker marker = MarkerFactory.getMarker("marker");
             LoggerFactory.getLogger("com.example.app").info(marker, "Application log");
-            Thread.sleep(100); // Need to wait, because the logger is async
+            // Need to wait, because the logger is async
+            await().atMost(1, TimeUnit.SECONDS).until(() -> !redirectedStream.toString().isEmpty());
 
             JsonNode jsonNode = objectMapper.readTree(redirectedStream.toString());
-            assertThat(jsonNode).isNotNull();
             assertThat(jsonNode.get("timestamp").isTextual()).isTrue();
             assertThat(jsonNode.get("level").asText()).isEqualTo("INFO");
             assertThat(jsonNode.get("logger").asText()).isEqualTo("com.example.app");
@@ -204,10 +205,10 @@ public void testLogAccessJsonToConsole() throws Exception {
             when(response.getHeader("Server")).thenReturn("Apache/2.4.12");
 
             requestLog.log(request, response);
-            Thread.sleep(100); // Need to wait, because the logger is async
+            // Need to wait, because the logger is async
+            await().atMost(1, TimeUnit.SECONDS).until(() -> !redirectedStream.toString().isEmpty());
 
             JsonNode jsonNode = objectMapper.readTree(redirectedStream.toString());
-            assertThat(jsonNode).isNotNull();
             assertThat(jsonNode.get("timestamp").isNumber()).isTrue();
             assertThat(jsonNode.get("requestTime").isNumber()).isTrue();
             assertThat(jsonNode.get("remoteAddress").asText()).isEqualTo("10.0.0.1");