Retry assertion for 10 seconds before failing

Also reduce the time 250 ms (instead of 1 second previously) between
retries to hopefully reduce the test duration on quick enough setups,
and still degrade nicely on less performing ones.

test/pom.xml

@@ -198,6 +198,12 @@ THE SOFTWARE.
       <version>4.0</version>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.awaitility</groupId>
+      <artifactId>awaitility</artifactId>
+      <version>3.0.0</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>

test/src/test/java/hudson/cli/QuietDownCommandTest.java

@@ -50,6 +50,7 @@ import java.util.concurrent.atomic.AtomicInteger;
 import static hudson.cli.CLICommandInvoker.Matcher.failedWith;
 import static hudson.cli.CLICommandInvoker.Matcher.hasNoStandardOutput;
 import static hudson.cli.CLICommandInvoker.Matcher.succeededSilently;
+import static org.awaitility.Awaitility.await;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
@@ -213,7 +214,6 @@ public class QuietDownCommandTest {
         try {
             threadPool.submit(exec_task);
             beforeCli.block();
-            Thread.sleep(1000); // Left a room for calling CLI
             assertJenkinsInQuietMode();
             exec_task.get(10, TimeUnit.SECONDS);
         } catch (TimeoutException e) {
@@ -259,7 +259,6 @@ public class QuietDownCommandTest {
         try {
             threadPool.submit(exec_task);
             beforeCli.block();
-            Thread.sleep(1000); // Left a room for calling CLI
             assertJenkinsInQuietMode();
             exec_task.get(10, TimeUnit.SECONDS);
         } catch (TimeoutException e) {
@@ -307,7 +306,6 @@ public class QuietDownCommandTest {
         });
         threadPool.submit(exec_task);
         beforeCli.block();
-        Thread.sleep(1000); // Left a room for calling CLI
         assertJenkinsInQuietMode();
         try {
             exec_task.get(2*TIMEOUT, TimeUnit.MILLISECONDS);
@@ -351,7 +349,6 @@ public class QuietDownCommandTest {
         });
         threadPool.submit(exec_task);
         beforeCli.block();
-        Thread.sleep(1000); // Left a room for calling CLI
         assertJenkinsInQuietMode();
         final boolean timeout_occured = false;
         try {
@@ -400,7 +397,6 @@ public class QuietDownCommandTest {
         });
         threadPool.submit(exec_task);
         beforeCli.block();
-        Thread.sleep(1000); // Left a room for calling CLI
         assertJenkinsInQuietMode();
 
         finish.signal();
@@ -427,7 +423,6 @@ public class QuietDownCommandTest {
         final Future<FreeStyleBuild> build = OnlineNodeCommandTest.startBlockingAndFinishingBuild(project, finish);
         assertThat(((FreeStyleProject) j.jenkins.getItem("aProject")).getBuilds(), hasSize(1));
 
-        boolean timeoutOccurred = false;
         final FutureTask exec_task = new FutureTask(new Callable() {
             public Object call() {
                 assertJenkinsNotInQuietMode();
@@ -445,7 +440,6 @@ public class QuietDownCommandTest {
         });
         threadPool.submit(exec_task);
         beforeCli.block();
-        Thread.sleep(1000); // Left a room for calling CLI
         assertJenkinsInQuietMode();
 
         finish.signal();
@@ -457,19 +451,39 @@ public class QuietDownCommandTest {
         exec_task.get(1, TimeUnit.SECONDS);
     }
 
+    /**
+     * Asserts if Jenkins is in quiet mode.
+     * Will retry for some time before actually failing.
+     */
     private final void assertJenkinsInQuietMode() {
         assertJenkinsInQuietMode(j);
     }
 
+    /**
+     * Asserts if Jenkins is <strong>not</strong> in quiet mode.
+     * Will retry for some time before actually failing.
+     */
     private final void assertJenkinsNotInQuietMode() {
         assertJenkinsNotInQuietMode(j);
     }
 
+    /**
+     * Asserts if Jenkins is in quiet mode, retrying for some time before failing.
+     * @throws TimeoutException
+     */
     public static final void assertJenkinsInQuietMode(final JenkinsRule j) {
-        assertThat(j.jenkins.getActiveInstance().getQueue().isBlockedByShutdown(task), equalTo(true));
+        await().pollInterval(250, TimeUnit.MILLISECONDS)
+                .atMost(10, TimeUnit.SECONDS)
+                .until(() -> j.jenkins.getActiveInstance().getQueue().isBlockedByShutdown(task));
     }
 
+    /**
+     * Asserts if Jenkins is <strong>not</strong> in quiet mode, retrying for some time before failing.
+     * @throws TimeoutException
+     */
     public static final void assertJenkinsNotInQuietMode(final JenkinsRule j) {
-        assertThat(j.jenkins.getActiveInstance().getQueue().isBlockedByShutdown(task), equalTo(false));
+        await().pollInterval(250, TimeUnit.MILLISECONDS)
+                .atMost(10, TimeUnit.SECONDS)
+                .until(() -> !j.jenkins.getActiveInstance().getQueue().isBlockedByShutdown(task));
     }
 }