The unit test code for Java Spark doesn't work, but the spark run with the same code runs fine

I am trying to write some unit testing for my Java Spark code. Below are my first simple try

public class SparkHelperTest {

    private JavaSparkContext sparkCtx;

    @Before
    public void setUp() throws IllegalArgumentException, IOException {
        SparkConf conf = new SparkConf();
        conf.setMaster("local[2]");
        conf.setAppName("sparkHelperTest");
        sparkCtx = new JavaSparkContext(conf);
    }

    @Test
    public void test() {
        final List<Integer> nums = new ArrayList<Integer>();
        nums.add(3);
        nums.add(4);
        nums.add(2);
        JavaRDD<Integer> rdd = sparkCtx.parallelize(nums,1);
        assertEquals(3, rdd.count());
    }
}

However I got this error

java.lang.NoClassDefFoundError: com/sun/jersey/spi/container/servlet/ServletContainer
        at org.apache.spark.status.api.v1.ApiRootResource$.getServletHandler(ApiRootResource.scala:187)
        at org.apache.spark.ui.SparkUI.initialize(SparkUI.scala:70)
        at org.apache.spark.ui.SparkUI.<init>(SparkUI.scala:76)
        at org.apache.spark.ui.SparkUI$.create(SparkUI.scala:195)
        at org.apache.spark.ui.SparkUI$.createLiveUI(SparkUI.scala:146)
        at org.apache.spark.SparkContext.<init>(SparkContext.scala:473)
        at org.apache.spark.api.java.JavaSparkContext.<init>(JavaSparkContext.scala:59)
        at com.firsttry.spark.SparkHelperTest.setUp(SparkHelperTest.java:29)
        ......
        at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
        at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
        at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
        at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
    Caused by: java.lang.ClassNotFoundException: com.sun.jersey.spi.container.servlet.ServletContainer
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        ... 30 more

I googled online and basically it is because the jersey version 1 is required. However, I found the jersey v1 was commented in our build.gradle as below

compile (
            'io.dropwizard:dropwizard-core:' + dropwizardVersion,
            ......
)
compile('org.apache.spark:spark-core_2.10:' + sparkVersion) {
        exclude group: 'org.apache.hadoop', module: 'hadoop-common'
}    
configurations.all {
        // all v1 versions of jersey should be excluded. Spark has some of these dependencies
        exclude group: 'com.sun.jersey', module: 'jersey-server'
        ......
}

if I commented this "exclude group: 'com.sun.jersey', module: 'jersey-server'", this error will be gone for unit test. However, after I build the task and run the spark job, I will got another error (note that with this "exclude", the spark job is running fine, so I guess there is a reason people put this exclude there). However, the mystery is if I simply copy the code in the test() method of the unit testing into the "normal run" code, the spark job is also running fine without requiring this jersey v1 issue. Can any body help, please?