Added some simple tests of the command line API

It's not *properly* testing anything, but it does check that things are
not totally silly.

Note that this code is currently unavoidably impacted by:
* stefanbirkner/system-lambda#27
* https://bugs.openjdk.org/browse/JDK-8199704

SpiNNaker-front-end/pom.xml

@@ -91,6 +91,10 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 			<groupId>info.picocli</groupId>
 			<artifactId>picocli</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>com.github.stefanbirkner</groupId>
+			<artifactId>system-lambda</artifactId>
+		</dependency>
 	</dependencies>
 	<description>The front-end interface. NB: not a GUI!</description>
 	<name>SpiNNaker Front End Interface</name>

SpiNNaker-front-end/src/main/java/uk/ac/manchester/spinnaker/front_end/CommandLineInterface.java

@@ -142,8 +142,9 @@ public static void main(String... args) {
 		var cmd = new CommandLine(new CommandLineInterface());
 		if (args.length == 0) {
 			cmd.usage(cmd.getErr());
+			System.exit(USAGE);
 		} else {
-			cmd.execute(args);
+			System.exit(cmd.execute(args));
 		}
 	}
 

SpiNNaker-front-end/src/test/java/uk/ac/manchester/spinnaker/front_end/TestFrontEnd.java

@@ -16,17 +16,70 @@
  */
 package uk.ac.manchester.spinnaker.front_end;
 
+import static com.github.stefanbirkner.systemlambda.SystemLambda.catchSystemExit;
+import static com.github.stefanbirkner.systemlambda.SystemLambda.tapSystemOutNormalized;
+import static java.lang.String.format;
 import static org.junit.jupiter.api.Assertions.*;
 
-import org.junit.jupiter.api.Disabled;
+import java.util.List;
+
 import org.junit.jupiter.api.Test;
 
 class TestFrontEnd {
 
+	/**
+	 * Run the command line, trapping its exit and comparing it with an expected
+	 * value.
+	 * <p>
+	 * This produces <em>one non-suppressable warning</em> due to
+	 * deprecation-for-removal in Java 17.
+	 *
+	 * @param expectedCode
+	 *            The expected exit code.
+	 * @param args
+	 *            The arguments to pass to the command line.
+	 * @throws Exception
+	 *             If anything goes wrong.
+	 * @see <a href="https://github.com/stefanbirkner/system-lambda/issues/27">
+	 *      System Lambda Issue #27</a>
+	 * @see <a href="https://bugs.openjdk.org/browse/JDK-8199704">JDK Issue
+	 *      #8199704</a>
+	 */
+	private static void runExpecting(int expectedCode, String... args)
+			throws Exception {
+		int code = catchSystemExit(() -> CommandLineInterface.main(args));
+		assertEquals(expectedCode, code);
+	}
+
+	@Test
+	void testHelp() throws Exception {
+		var msg = tapSystemOutNormalized(() -> {
+			runExpecting(0, "help");
+		});
+		var requiredSubcommands = List.of("dse_app_mon", "gather");
+		var requiredArgs = List.of("<machineFile>", "<runFolder>");
+		for (var cmd: requiredSubcommands) {
+			assertTrue(msg.contains(cmd),
+					() -> format("help message does not contain '%s': %s", cmd,
+							msg));
+			var msg2 = tapSystemOutNormalized(() -> {
+				runExpecting(0, "help", cmd);
+			});
+			for (var arg : requiredArgs) {
+				assertTrue(msg2.contains(arg),
+						() -> format("help message does not contain '%s': %s",
+								arg, msg2));
+			}
+		}
+	}
+
 	@Test
-	@Disabled("Not yet implemented")
-	void test() {
-		fail("Not yet implemented");
+	void testVersion() throws Exception {
+		var msg = tapSystemOutNormalized(() -> {
+			runExpecting(0, "--version");
+		});
+		assertTrue(msg.contains(" version "),
+				() -> format("message '%s' does not contain 'version'", msg));
 	}
 
 }

pom.xml

@@ -345,6 +345,12 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 				<artifactId>javax.el</artifactId>
 				<version>3.0.0</version>
 			</dependency>
+			<dependency>
+				<groupId>com.github.stefanbirkner</groupId>
+				<artifactId>system-lambda</artifactId>
+				<version>1.2.1</version>
+				<scope>test</scope>
+			</dependency>
 		</dependencies>
 	</dependencyManagement>