diff --git a/skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/api/logging/WriterFactory.java b/skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/api/logging/WriterFactory.java
index 3571aaa06dadbd585cbb1e5d32eea766e9beb5b3..fc38edfeebf34ccb3b7052e02834835690cde687 100644
--- a/skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/api/logging/WriterFactory.java
+++ b/skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/api/logging/WriterFactory.java
@@ -3,9 +3,6 @@ package com.a.eye.skywalking.api.logging;
 import com.a.eye.skywalking.api.conf.Config;
 
 public class WriterFactory {
-    private WriterFactory(){
-    }
-
     public static IWriter getLogWriter(){
         if (Config.SkyWalking.IS_PREMAIN_MODE){
             return SyncFileWriter.instance();
diff --git a/skywalking-sniffer/skywalking-api/src/test/java/com/a/eye/skywalking/api/logging/EasyLogResolverTest.java b/skywalking-sniffer/skywalking-api/src/test/java/com/a/eye/skywalking/api/logging/EasyLogResolverTest.java
new file mode 100644
index 0000000000000000000000000000000000000000..f4f6077b6cdf8f3e6dacc09001218e6c0e736009
--- /dev/null
+++ b/skywalking-sniffer/skywalking-api/src/test/java/com/a/eye/skywalking/api/logging/EasyLogResolverTest.java
@@ -0,0 +1,14 @@
+package com.a.eye.skywalking.api.logging;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Created by wusheng on 2017/2/28.
+ */
+public class EasyLogResolverTest {
+    @Test
+    public void testGetLogger(){
+        Assert.assertTrue(new EasyLogResolver().getLogger(EasyLogResolverTest.class) instanceof EasyLogger);
+    }
+}
diff --git a/skywalking-sniffer/skywalking-api/src/test/java/com/a/eye/skywalking/api/logging/EasyLoggerTest.java b/skywalking-sniffer/skywalking-api/src/test/java/com/a/eye/skywalking/api/logging/EasyLoggerTest.java
new file mode 100644
index 0000000000000000000000000000000000000000..0e6cd274c38d5d0e06d4db452c7225e7983dd9ed
--- /dev/null
+++ b/skywalking-sniffer/skywalking-api/src/test/java/com/a/eye/skywalking/api/logging/EasyLoggerTest.java
@@ -0,0 +1,64 @@
+package com.a.eye.skywalking.api.logging;
+
+import com.a.eye.skywalking.api.conf.Config;
+import java.io.PrintStream;
+import org.junit.AfterClass;
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.mockito.Mockito;
+
+import static org.mockito.Matchers.anyString;
+import static org.mockito.Mockito.times;
+
+/**
+ * Created by wusheng on 2017/2/28.
+ */
+public class EasyLoggerTest {
+    private static PrintStream outRef;
+    private static PrintStream errRef;
+
+    @BeforeClass
+    public static void initAndHoldOut(){
+        outRef = System.out;
+        errRef = System.err;
+    }
+
+    @Test
+    public void testLog(){
+        Config.SkyWalking.IS_PREMAIN_MODE = false;
+
+        PrintStream output = Mockito.mock(PrintStream.class);
+        System.setOut(output);
+        PrintStream err = Mockito.mock(PrintStream.class);
+        System.setErr(err);
+        EasyLogger logger = new EasyLogger(EasyLoggerTest.class);
+
+        Assert.assertTrue(logger.isDebugEnable());
+        Assert.assertTrue(logger.isInfoEnable());
+        Assert.assertTrue(logger.isWarnEnable());
+        Assert.assertTrue(logger.isErrorEnable());
+
+        logger.debug("hello world");
+        logger.debug("hello {}", "world");
+        logger.info("hello world");
+        logger.info("hello {}", "world");
+
+        logger.warn("hello {}", "world");
+        logger.warn("hello world");
+        logger.error("hello world");
+        logger.error("hello world", new NullPointerException());
+        logger.error(new NullPointerException(),"hello {}", "world");
+
+        Mockito.verify(output,times(4))
+            .println(anyString());
+        Mockito.verify(err,times(7))
+            .println(anyString());
+    }
+
+    @AfterClass
+    public static void reset(){
+        System.setOut(outRef);
+        System.setErr(errRef);
+    }
+}
diff --git a/skywalking-sniffer/skywalking-api/src/test/java/com/a/eye/skywalking/api/logging/WriterFactoryTest.java b/skywalking-sniffer/skywalking-api/src/test/java/com/a/eye/skywalking/api/logging/WriterFactoryTest.java
new file mode 100644
index 0000000000000000000000000000000000000000..eec580928a95edccdff1539400afb73333bf1e27
--- /dev/null
+++ b/skywalking-sniffer/skywalking-api/src/test/java/com/a/eye/skywalking/api/logging/WriterFactoryTest.java
@@ -0,0 +1,42 @@
+package com.a.eye.skywalking.api.logging;
+
+import com.a.eye.skywalking.api.conf.Config;
+import java.io.PrintStream;
+import org.junit.AfterClass;
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.mockito.Mockito;
+
+/**
+ * Created by wusheng on 2017/2/28.
+ */
+public class WriterFactoryTest {
+    private static PrintStream errRef;
+
+    @BeforeClass
+    public static void initAndHoldOut(){
+        errRef = System.err;
+    }
+
+    /**
+     * During this test case,
+     * reset {@link System#out} to a Mock object, for avoid a console system.error.
+     */
+    @Test
+    public void testGetLogWriter(){
+        Config.SkyWalking.IS_PREMAIN_MODE = true;
+        PrintStream mockStream = Mockito.mock(PrintStream.class);
+        System.setErr(mockStream);
+        Assert.assertEquals(SyncFileWriter.instance(), WriterFactory.getLogWriter());
+
+        Config.SkyWalking.IS_PREMAIN_MODE = false;
+        Assert.assertTrue(WriterFactory.getLogWriter() instanceof STDOutWriter);
+    }
+
+    @AfterClass
+    public static void reset(){
+        Config.SkyWalking.IS_PREMAIN_MODE = false;
+        System.setErr(errRef);
+    }
+}