Add skywalking-commons test cases.

skywalking-commons/skywalking-util/src/test/java/com/a/eye/skywalking/api/util/ConfigInitializerTest.java

+package com.a.eye.skywalking.api.util;
+
+import java.util.Properties;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * Created by wusheng on 2017/2/27.
+ */
+public class ConfigInitializerTest {
+    @Test
+    public void testInitialize() throws IllegalAccessException {
+        Properties properties = new Properties();
+        properties.put("Level1Object.strAttr".toLowerCase(), "stringValue");
+        properties.put("Level1Object.Level2Object.intAttr".toLowerCase(), "1000");
+        properties.put("Level1Object.Level2Object.longAttr".toLowerCase(), "1000");
+        properties.put("Level1Object.Level2Object.booleanAttr".toLowerCase(), "true");
+
+        ConfigInitializer.initialize(properties, TestPropertiesObject.class);
+
+        Assert.assertEquals("stringValue", TestPropertiesObject.Level1Object.strAttr);
+        Assert.assertEquals(1000, TestPropertiesObject.Level1Object.Level2Object.intAttr);
+        Assert.assertEquals(1000L, TestPropertiesObject.Level1Object.Level2Object.longAttr);
+        Assert.assertEquals(true, TestPropertiesObject.Level1Object.Level2Object.booleanAttr);
+    }
+
+    @Test
+    public void testInitializeWithUnsupportedConfig() throws IllegalAccessException {
+        Properties properties = new Properties();
+        properties.put("Level1Object.noExistAttr".toLowerCase(), "stringValue");
+
+        ConfigInitializer.initialize(properties, TestPropertiesObject.class);
+
+        Assert.assertNull(TestPropertiesObject.Level1Object.strAttr);
+    }
+
+    @Before
+    public void clear(){
+        TestPropertiesObject.Level1Object.strAttr = null;
+        TestPropertiesObject.Level1Object.Level2Object.intAttr = 0;
+        TestPropertiesObject.Level1Object.Level2Object.longAttr = 0;
+        TestPropertiesObject.Level1Object.Level2Object.booleanAttr = false;
+    }
+
+    public static class TestPropertiesObject {
+        public static class Level1Object {
+            public static String strAttr = null;
+
+            public static class Level2Object {
+                public static int intAttr = 0;
+
+                public static long longAttr;
+
+                public static boolean booleanAttr;
+            }
+        }
+    }
+}

skywalking-commons/skywalking-util/src/test/java/com/a/eye/skywalking/api/util/StringUtilTest.java

+package com.a.eye.skywalking.api.util;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Created by wusheng on 2017/2/27.
+ */
+public class StringUtilTest {
+    @Test
+    public void testIsEmpty(){
+        Assert.assertTrue(StringUtil.isEmpty(null));
+        Assert.assertTrue(StringUtil.isEmpty(""));
+        Assert.assertFalse(StringUtil.isEmpty("   "));
+        Assert.assertFalse(StringUtil.isEmpty("A String"));
+    }
+
+    @Test
+    public void testJoin(){
+        Assert.assertNull(StringUtil.join('.'));
+        Assert.assertEquals("Single part.", StringUtil.join('.', "Single part."));
+        Assert.assertEquals("part1.part2.p3", StringUtil.join('.', "part1", "part2", "p3"));
+    }
+}