使用mock对象一个举例

 package cn.com.rzx.test;
public class A
{
 private BInterfance bInterfance;
 public A(BInterfance bInterfance)
 {
  this.bInterfance = bInterfance;
 }
 public String testMethod(String str)
 {

  return str + bInterfance.getString("b");
 }
}

package cn.com.rzx.test;
public class B implements BInterfance
{
 public String getString(String str){
  return str+"77777777";
 }
}

package cn.com.rzx.test;
public interface BInterfance
{
 public String getString(String str);
}

package cn.com.rzx.test;
public class MockB implements BInterfance
{
 private String str;
 public String getString(String str){
  return str;
 } 
 public void setString(String str){
  this.str = str;
 }
}

package cn.com.rzx.test;
import junit.framework.TestCase;
public class ATest extends TestCase
{
 protected BInterfance mock;
 protected A a;
 protected void setUp() throws Exception
 {
  super.setUp();
  mock = new MockB();
  a = new A(mock);  
 }

 /*
  * “cn.com.rzx.test.A.testMethod(String)”的测试方法
  */
 public void testTestMethod()
 {
  assertEquals(a.testMethod("a"), "ab");
 }

}