Add test for --help capability output

test/jdk/tools/jlink/JLinkHelpCapabilityTest.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2024, Red Hat, Inc.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import java.util.spi.ToolProvider;
+
+/*
+ * @test id="run-time-image-cap-yes"
+ * @summary Test jlink --help for capability output (true)
+ * @requires (vm.compMode != "Xcomp" & jlink.runtime.linkable)
+ * @run main/othervm JLinkHelpCapabilityTest true
+ */
+
+/*
+ * @test id="run-time-image-cap-no"
+ * @summary Test jlink --help for capability output (false)
+ * @requires (vm.compMode != "Xcomp" & !jlink.runtime.linkable)
+ * @run main/othervm JLinkHelpCapabilityTest false
+ */
+public class JLinkHelpCapabilityTest {
+    static final ToolProvider JLINK_TOOL = ToolProvider.findFirst("jlink")
+        .orElseThrow(() ->
+            new RuntimeException("jlink tool not found")
+        );
+
+    public static void main(String[] args) throws Exception {
+        boolean runtimeLinkCap = Boolean.parseBoolean(args[0]);
+        String capabilities = String.format("Capabilities: %srun-time-image",
+                                            runtimeLinkCap ? "+" : "-");
+        {
+            // Verify capability in --help output
+            StringWriter writer = new StringWriter();
+            PrintWriter pw = new PrintWriter(writer);
+            JLINK_TOOL.run(pw, pw, "--help");
+            String output = writer.toString().trim();
+            String lines[] = output.split("\n");
+            if (!capabilities.equals(lines[lines.length - 1])) {
+                System.err.println(output);
+                throw new AssertionError("'--help': Capabilities mismatch. Expected: '" + capabilities +"'");
+            }
+        }
+    }
+}