Allow tests to System.exit() by default

Otherwise the ApplicationContext stays alive and if it's a
server app the JVM does not exit at the end of "spring test".
User can override with "spring test foo.groovy --nohup"
(which we have to do in our unit tests).

spring-boot-cli/src/main/java/org/springframework/boot/cli/SpringCli.java

@@ -50,6 +50,7 @@ public class SpringCli {
 
 		int exitCode = runner.runAndHandleErrors(args);
 		if (exitCode != 0) {
+			// If successful, leave it to run in case it's a server app
 			System.exit(exitCode);
 		}
 	}

spring-boot-cli/src/main/java/org/springframework/boot/cli/command/test/TestCommand.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.cli.command.test;
 
 import joptsimple.OptionSet;
+import joptsimple.OptionSpec;
 
 import org.springframework.boot.cli.command.Command;
 import org.springframework.boot.cli.command.OptionParsingCommand;
@@ -45,6 +46,12 @@ public class TestCommand extends OptionParsingCommand {
 
 		private TestRunner runner;
 
+		@Override
+		protected void doOptions() {
+			option("nohup",
+					"Flag to indicate that the JVM should not exit when tests are finished");
+		}
+
 		@Override
 		protected void run(OptionSet options) throws Exception {
 			SourceOptions sourceOptions = new SourceOptions(options);
@@ -53,6 +60,9 @@ public class TestCommand extends OptionParsingCommand {
 			this.runner = new TestRunner(configuration, sourceOptions.getSourcesArray(),
 					sourceOptions.getArgsArray());
 			this.runner.compileAndRunTests();
+			if (!options.has("nohup")) {
+				System.exit(0); // TODO: non-zero if test fails?
+			}
 		}
 
 		/**