diff --git a/src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlShowTest_table.java b/src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlShowTest_table.java
index 9eb377e788..562071ff2b 100644
--- a/src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlShowTest_table.java
+++ b/src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlShowTest_table.java
@@ -21,9 +21,6 @@ import org.junit.Assert;
 
 import com.alibaba.druid.sql.MysqlTest;
 import com.alibaba.druid.sql.ast.SQLStatement;
-import com.alibaba.druid.sql.ast.statement.SQLSelect;
-import com.alibaba.druid.sql.ast.statement.SQLSelectStatement;
-import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlSelectQueryBlock;
 import com.alibaba.druid.sql.dialect.mysql.parser.MySqlStatementParser;
 import com.alibaba.druid.sql.dialect.mysql.visitor.MySqlSchemaStatVisitor;
 
diff --git a/src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlUpdateTest_0.java b/src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlUpdateTest_0.java
index c48fd19eb4..031534e12d 100644
--- a/src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlUpdateTest_0.java
+++ b/src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlUpdateTest_0.java
@@ -17,7 +17,7 @@ package com.alibaba.druid.bvt.sql.mysql;
 
 import java.util.List;
 
-import junit.framework.Assert;
+import org.junit.Assert;
 
 import com.alibaba.druid.sql.MysqlTest;
 import com.alibaba.druid.sql.ast.SQLStatement;
diff --git a/src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlUpdateTest_1.java b/src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlUpdateTest_1.java
index 6e2669b862..2c5e2394ce 100644
--- a/src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlUpdateTest_1.java
+++ b/src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlUpdateTest_1.java
@@ -17,14 +17,13 @@ package com.alibaba.druid.bvt.sql.mysql;
 
 import java.util.List;
 
-import junit.framework.Assert;
+import org.junit.Assert;
 
 import com.alibaba.druid.sql.MysqlTest;
 import com.alibaba.druid.sql.ast.SQLStatement;
 import com.alibaba.druid.sql.dialect.mysql.parser.MySqlStatementParser;
 import com.alibaba.druid.sql.dialect.mysql.visitor.MySqlSchemaStatVisitor;
 import com.alibaba.druid.stat.TableStat;
-import com.alibaba.druid.stat.TableStat.Column;
 
 public class MySqlUpdateTest_1 extends MysqlTest {
 
diff --git a/src/test/java/com/alibaba/druid/bvt/sql/mysql/NumberTest.java b/src/test/java/com/alibaba/druid/bvt/sql/mysql/NumberTest.java
index 2eb21df5a7..313d99527f 100644
--- a/src/test/java/com/alibaba/druid/bvt/sql/mysql/NumberTest.java
+++ b/src/test/java/com/alibaba/druid/bvt/sql/mysql/NumberTest.java
@@ -17,9 +17,10 @@ package com.alibaba.druid.bvt.sql.mysql;
 
 import java.util.List;
 
-import junit.framework.Assert;
 import junit.framework.TestCase;
 
+import org.junit.Assert;
+
 import com.alibaba.druid.sql.ast.SQLStatement;
 import com.alibaba.druid.sql.dialect.mysql.parser.MySqlStatementParser;
 import com.alibaba.druid.sql.dialect.mysql.visitor.MySqlOutputVisitor;
diff --git a/src/test/java/com/alibaba/druid/stat/JdbcSqlStatTest.java b/src/test/java/com/alibaba/druid/stat/JdbcSqlStatTest.java
index ef6f196b0c..2dcfc2a6e4 100644
--- a/src/test/java/com/alibaba/druid/stat/JdbcSqlStatTest.java
+++ b/src/test/java/com/alibaba/druid/stat/JdbcSqlStatTest.java
@@ -13,7 +13,7 @@ public class JdbcSqlStatTest extends TestCase {
         gc();
         long memoryStart = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getUsed();
 
-        final int COUNT = 1024 * 1024;
+        final int COUNT = 1000 * 5;
         JdbcSqlStat[] items = new JdbcSqlStat[COUNT];
         for (int i = 0; i < COUNT; ++i) {
             items[i] = new JdbcSqlStat("");
diff --git a/src/test/java/com/alibaba/druid/stat/JdbcSqlStatTest1.java b/src/test/java/com/alibaba/druid/stat/JdbcSqlStatTest1.java
new file mode 100644
index 0000000000..ce0978f7af
--- /dev/null
+++ b/src/test/java/com/alibaba/druid/stat/JdbcSqlStatTest1.java
@@ -0,0 +1,37 @@
+package com.alibaba.druid.stat;
+
+import java.lang.management.ManagementFactory;
+import java.text.NumberFormat;
+
+import junit.framework.TestCase;
+
+public class JdbcSqlStatTest1 extends TestCase {
+
+    private JdbcDataSourceStat dataSourceStat = new JdbcDataSourceStat("", "");
+
+    public void test_0() throws Exception {
+        for (int i = 0; i < 3; ++i) {
+            gc();
+            long memoryStart = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getUsed();
+
+            final int COUNT = 1024 * 1024;
+            for (int j = 0; j < COUNT; ++j) {
+                dataSourceStat.createSqlStat(Integer.toString(j));
+                // items[i] = Histogram.makeHistogram(20);
+            }
+            gc();
+
+            long memoryEnd = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getUsed();
+
+            System.out.println("memory used : " + NumberFormat.getInstance().format(memoryStart));
+            System.out.println("memory used : " + NumberFormat.getInstance().format(memoryEnd));
+            System.out.println("memory used : " + NumberFormat.getInstance().format(memoryEnd - memoryStart));
+        }
+    }
+
+    private void gc() {
+        for (int i = 0; i < 10; ++i) {
+            System.gc();
+        }
+    }
+}