add DataSourceClosedException

src/test/java/com/alibaba/druid/bvt/pool/ClosedTest.java

@@ -0,0 +1,32 @@
+package com.alibaba.druid.bvt.pool;
+
+import java.sql.Connection;
+
+import junit.framework.Assert;
+import junit.framework.TestCase;
+
+import com.alibaba.druid.pool.DataSourceClosedException;
+import com.alibaba.druid.pool.DruidDataSource;
+
+public class ClosedTest extends TestCase {
+
+    public void test_close() throws Exception {
+        DruidDataSource dataSource = new DruidDataSource();
+        dataSource.setUrl("jdbc:mock:xxx");
+
+        Connection conn = dataSource.getConnection();
+        conn.close();
+
+        dataSource.close();
+
+        DataSourceClosedException error = null;
+
+        try {
+            dataSource.getConnection();
+        } catch (DataSourceClosedException ex) {
+            error = ex;
+        }
+
+        Assert.assertNotNull(error);
+    }
+}