Issue gh-50

Author: rwinch

spring-boot-testjars/src/test/java/org/springframework/experimental/boot/server/exec/CommonsExecWebServerFactoryBeanTests.java

@@ -23,6 +23,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Map;
 
 import org.junit.jupiter.api.Test;
 
@@ -101,6 +102,15 @@ void doesNotAddJarLauncherDetectorLauncherDetectorWhenMainClassDefined() throws
 		server.destroy();
 	}
 
+	@Test
+	void serverPortWhenSpecifiedThenNotOverridden() throws Exception {
+		String expectedPort = "1234";
+		String portSystemProperty = "server.port";
+		CommonsExecWebServer server = CommonsExecWebServerFactoryBean.builder()
+				.addSystemProperties(Map.of(portSystemProperty, expectedPort)).getObject();
+		assertThat(server.getCommandLine().getArguments()).contains("-D" + portSystemProperty + "=" + expectedPort);
+	}
+
 	private static URLClassLoader getClassLoaderFromArgs(String classpathArgs) throws MalformedURLException {
 		var paths = new ArrayList<URL>();
 		for (String path : classpathArgs.split(":")) {