diff --git a/src/main/java/com/alibaba/druid/mock/MockConnection.java b/src/main/java/com/alibaba/druid/mock/MockConnection.java
index 6e69d46bca..362a69f12e 100644
--- a/src/main/java/com/alibaba/druid/mock/MockConnection.java
+++ b/src/main/java/com/alibaba/druid/mock/MockConnection.java
@@ -66,7 +66,9 @@ public class MockConnection implements Connection {
         this.driver = driver;
         this.connectProperties = connectProperties;
 
-        this.id = driver.generateConnectionId();
+        if (driver != null) {
+            this.id = driver.generateConnectionId();
+        }
     }
 
     public long getId() {
diff --git a/src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java b/src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java
index b0cd135105..669fa27248 100644
--- a/src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java
+++ b/src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java
@@ -62,7 +62,7 @@ public abstract class DruidAbstractDataSource implements DruidAbstractDataSource
     public final static boolean      DEFAULT_WHILE_IDLE                        = false;
     public static final long         DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS = -1L;
     public static final long         DEFAULT_TIME_BETWEEN_CONNECT_ERROR_MILLIS = 30 * 1000;
-    public static final int          DEFAULT_NUM_TESTS_PER_EVICTION_RUN        = 1;
+    public static final int          DEFAULT_NUM_TESTS_PER_EVICTION_RUN        = 3;
 
     /**
      * The default value for {@link #getMinEvictableIdleTimeMillis}.
diff --git a/src/main/java/com/alibaba/druid/pool/DruidDataSource.java b/src/main/java/com/alibaba/druid/pool/DruidDataSource.java
index 507cc44840..c2ae2ee8d6 100644
--- a/src/main/java/com/alibaba/druid/pool/DruidDataSource.java
+++ b/src/main/java/com/alibaba/druid/pool/DruidDataSource.java
@@ -761,6 +761,9 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
                         } finally {
                             lock.unlock();
                         }
+                        if (LOG.isDebugEnabled()) {
+                            LOG.debug("checked " + size);
+                        }
                     }
 
                     for (ConnectionHolder item : evictList) {
diff --git a/src/test/java/com/alibaba/druid/pool/dbcp/TestIdle.java b/src/test/java/com/alibaba/druid/pool/dbcp/TestIdle.java
index 28fadb2cb2..67ee3a83c3 100644
--- a/src/test/java/com/alibaba/druid/pool/dbcp/TestIdle.java
+++ b/src/test/java/com/alibaba/druid/pool/dbcp/TestIdle.java
@@ -22,11 +22,11 @@ public class TestIdle extends TestCase {
         dataSource.setUrl("jdbc:mock:xxx");
         dataSource.setDriverClassName("com.alibaba.druid.mock.MockDriver");
         dataSource.setInitialSize(1);
-        dataSource.setMaxActive(4);
-        dataSource.setMaxIdle(4);
+        dataSource.setMaxActive(5);
+        dataSource.setMaxIdle(5);
         dataSource.setMinIdle(0);
         dataSource.setMinEvictableIdleTimeMillis(5000 * 1);
-        dataSource.setTimeBetweenEvictionRunsMillis(1000);
+        dataSource.setTimeBetweenEvictionRunsMillis(500);
         dataSource.setTestWhileIdle(true);
         dataSource.setTestOnBorrow(false);
         dataSource.setValidationQuery("SELECT 1");
diff --git a/src/test/resources/log4j.properties b/src/test/resources/log4j.properties
index 64b595c698..bafd24e04a 100644
--- a/src/test/resources/log4j.properties
+++ b/src/test/resources/log4j.properties
@@ -27,6 +27,6 @@ log4j.category.java.sql.ResultSet=DEBUG
 log4j.category.org.codehaus.xfire=INFO
 log4j.category.httpclient=INFO
 log4j.category.org.apache.struts.action.ActionServlet=ERROR
-log4j.category.com.alibaba.druid.mock=ERROR
+#log4j.category.com.alibaba.druid.mock=ERROR
 
 log4j.rootLogger=TRACE,CONSOLE