Add a test case for SystemPropertiesTest.java (#8034)

Add a test case

test/src/test/java/jenkins/util/SystemPropertiesTest.java

@@ -31,6 +31,7 @@ import static org.hamcrest.Matchers.nullValue;
 import javax.servlet.ServletContextEvent;
 import org.eclipse.jetty.server.handler.ContextHandler;
 import org.hamcrest.Matchers;
+import org.junit.After;
 import org.junit.Assume;
 import org.junit.Before;
 import org.junit.Rule;
@@ -51,6 +52,12 @@ public class SystemPropertiesTest {
         new SystemProperties.Listener().contextInitialized(new ServletContextEvent(j.jenkins.servletContext));
     }
 
+    @After
+    public void tearDown() {
+        System.clearProperty("foo.bar");
+    }
+
+
     @Test
     public void shouldReturnNullIfUndefined() throws Exception {
         assertThat("Properties should be null by default",
@@ -81,6 +88,15 @@ public class SystemPropertiesTest {
                 SystemProperties.getString("install-wizard-path"), equalTo("myVal2"));
     }
 
+    @Test
+    public void shouldReturnWebAppPropertyIfSystemPropertyNotSetAndDefaultIsSet() throws Exception {
+        assertThat("Property is undefined before test",
+                SystemProperties.getString("foo.bar"), equalTo(null));
+        setWebAppInitParameter("foo.bar", "myVal");
+        assertThat("Should return web app property if system property is not set and default value is set",
+                SystemProperties.getString("foo.bar", "defaultVal"), equalTo("myVal"));
+    }
+
     /**
      * Hack to set a web app initial parameter afterwards. Only works with Jetty.
      * @param property property to set