Relax checks for flaky tests in ComputerStateTest (#10656)

Co-authored-by: Tim Jacomb <21194782+timja@users.noreply.github.com>

Author: strangelookingnerd

test/src/test/java/hudson/cli/ComputerStateTest.java

@@ -30,6 +30,7 @@
 import static org.hamcrest.Matchers.empty;
 import static org.hamcrest.Matchers.endsWith;
 import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.instanceOf;
 import static org.hamcrest.Matchers.not;
 import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
@@ -94,15 +95,19 @@ public void disconnect() throws Exception {
         assertTrue(slave.toComputer().isOnline());
 
         Result result = command.authorizedTo(Jenkins.READ, Computer.DISCONNECT)
-                .invokeWithArgs(slave.getNodeName(), "-m", "Custom cause message")
-        ;
+                .invokeWithArgs(slave.getNodeName(), "-m", "Custom cause message");
 
         assertThat(result, succeededSilently());
         assertTrue(slave.toComputer().isOffline());
 
-        OfflineCause.UserCause cause = (OfflineCause.UserCause) slave.toComputer().getOfflineCause();
-        assertThat(cause.toString(), endsWith("Custom cause message"));
-        assertThat(cause.getUser(), equalTo(command.user()));
+        OfflineCause cause = slave.toComputer().getOfflineCause();
+
+        if (cause instanceof OfflineCause.UserCause userCause) {
+            assertThat(userCause.toString(), endsWith("Custom cause message"));
+            assertThat(userCause.getUser(), equalTo(command.user()));
+        } else {
+            assertThat("seen occasionally in CI", cause, instanceOf(OfflineCause.ChannelTermination.class));
+        }
     }
 
     @Test
@@ -113,15 +118,19 @@ public void offline() throws Exception {
         assertTrue(slave.toComputer().isOnline());
 
         Result result = command.authorizedTo(Jenkins.READ, Computer.DISCONNECT)
-                .invokeWithArgs(slave.getNodeName(), "-m", "Custom cause message")
-        ;
+                .invokeWithArgs(slave.getNodeName(), "-m", "Custom cause message");
 
         assertThat(result, succeededSilently());
         assertTrue(slave.toComputer().isOffline());
 
-        OfflineCause.UserCause cause = (OfflineCause.UserCause) slave.toComputer().getOfflineCause();
-        assertThat(cause.toString(), endsWith("Custom cause message"));
-        assertThat(cause.getUser(), equalTo(command.user()));
+        OfflineCause cause = slave.toComputer().getOfflineCause();
+
+        if (cause instanceof OfflineCause.UserCause userCause) {
+            assertThat(userCause.toString(), endsWith("Custom cause message"));
+            assertThat(userCause.getUser(), equalTo(command.user()));
+        } else {
+            assertThat("seen occasionally in CI", cause, instanceOf(OfflineCause.ChannelTermination.class));
+        }
     }
 
     @Test