JNLPLauncherRealTest turned up need for jenkinsci/sshd-plugin#75

core/src/main/java/jenkins/model/identity/InstanceIdentityProvider.java

@@ -155,6 +155,7 @@ private KeyTypes(Class<PUB> pubKeyType, Class<PRIV> privKeyType) {
         private static <PUB extends PublicKey, PRIV extends PrivateKey> InstanceIdentityProvider<PUB, PRIV> get(
                 @NonNull KeyTypes<PUB, PRIV> type) {
             for (InstanceIdentityProvider provider : ExtensionList.lookup(InstanceIdentityProvider.class)) {
+                LOGGER.fine(() -> "loaded " + provider + " from " + provider.getClass().getProtectionDomain().getCodeSource().getLocation());
                 try {
                     KeyPair keyPair = provider.getKeyPair();
                     if (keyPair != null
@@ -174,6 +175,7 @@ private static <PUB extends PublicKey, PRIV extends PrivateKey> InstanceIdentity
                             "Instance identity provider " + provider + " propagated an uncaught exception", e);
                 }
             }
+            LOGGER.fine("no providers");
             return null;
         }
 

test/src/test/java/hudson/slaves/JNLPLauncherRealTest.java

@@ -0,0 +1,78 @@
+/*
+ * The MIT License
+ *
+ * Copyright 2022 CloudBees, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package hudson.slaves;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+
+import hudson.ExtensionList;
+import hudson.PluginWrapper;
+import hudson.model.FreeStyleBuild;
+import hudson.model.FreeStyleProject;
+import hudson.model.Slave;
+import hudson.util.FormValidation;
+import jenkins.slaves.JnlpSlaveAgentProtocol4;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.Description;
+import org.junit.runners.model.Statement;
+import org.jvnet.hudson.test.For;
+import org.jvnet.hudson.test.InboundAgentRule;
+import org.jvnet.hudson.test.Issue;
+import org.jvnet.hudson.test.JenkinsRule;
+import org.jvnet.hudson.test.RealJenkinsRule;
+
+@For({JNLPLauncher.class, JnlpSlaveAgentProtocol4.class})
+public class JNLPLauncherRealTest {
+
+    @Rule public RealJenkinsRule rr = new RealJenkinsRule().includeTestClasspathPlugins(false);
+
+    @Issue("JEP-230")
+    @Test public void smokes() throws Throwable {
+        /* Since RealJenkinsRuleInit.jpi will load detached plugins, to reproduce a failure use:
+        FileUtils.touch(new File(rr.getHome(), "plugins/instance-identity.jpi.disabled"));
+        */
+        rr.then(JNLPLauncherRealTest::_smokes);
+    }
+
+    private static void _smokes(JenkinsRule r) throws Throwable {
+        InboundAgentRule inboundAgents = new InboundAgentRule(); // cannot use @Rule since it would not be accessible from the controller JVM
+        inboundAgents.apply(new Statement() {
+            @Override public void evaluate() throws Throwable {
+                for (PluginWrapper plugin : r.jenkins.pluginManager.getPlugins()) {
+                    System.err.println(plugin + " active=" + plugin.isActive() + " enabled=" + plugin.isEnabled());
+                }
+                assertThat(ExtensionList.lookupSingleton(JNLPLauncher.DescriptorImpl.class).doCheckWebSocket(false, null).kind, is(FormValidation.Kind.OK));
+                Slave agent = inboundAgents.createAgent(r, "static");
+                FreeStyleProject p = r.createFreeStyleProject();
+                p.setAssignedNode(agent);
+                FreeStyleBuild b = r.buildAndAssertSuccess(p);
+                System.err.println(JenkinsRule.getLog(b));
+            }
+        }, Description.EMPTY).evaluate();
+
+    }
+
+}

war/pom.xml

@@ -411,7 +411,7 @@ THE SOFTWARE.
                 <artifactItem>
                   <groupId>org.jenkins-ci.modules</groupId>
                   <artifactId>sshd</artifactId>
-                  <version>3.1.0</version>
+                  <version>3.235.v2ee69617b_e92</version> <!-- https://github.com/jenkinsci/sshd-plugin/pull/75 -->
                   <type>hpi</type>
                 </artifactItem>
                 <artifactItem>