add ArrayUtils test case

core/src/test/java/com/taobao/arthas/core/util/ArrayUtilsTest.java

@@ -0,0 +1,40 @@
+package com.taobao.arthas.core.util;
+
+import org.junit.Assert;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+/**
+ * @author earayu
+ */
+public class ArrayUtilsTest {
+
+    @Rule
+    public ExpectedException thrown = ExpectedException.none();
+
+    @Test
+    public void testEmptyLongArray() {
+        Assert.assertArrayEquals(ArrayUtils.EMPTY_LONG_ARRAY, new long[0]);
+    }
+
+    @Test
+    public void testToPrimitive() {
+        Assert.assertArrayEquals(ArrayUtils.toPrimitive(null), null);
+        Assert.assertArrayEquals(ArrayUtils.toPrimitive(new Long[0]), new long[0]);
+        Assert.assertArrayEquals(
+                ArrayUtils.toPrimitive(new Long[]{
+                        1L,
+                        1763L,
+                        54769975464L
+                }),
+                new long[]{
+                        1L,
+                        1763L,
+                        54769975464L
+                });
+        //throws NullPointerException if array content is null
+        thrown.expect(NullPointerException.class);
+        Assert.assertArrayEquals(ArrayUtils.toPrimitive(new Long[]{null}), new long[]{1L});
+    }
+}