1. 加入依赖包（maven）

<dependency>
    <groupId>org.powermock</groupId>
    <artifactId>powermock-api-mockito</artifactId>
    <version>1.4.10</version>
    <scope>test</scope>
</dependency>
 
<dependency>
    <groupId>org.powermock</groupId>
    <artifactId>powermock-module-junit4</artifactId>
    <version>1.4.10</version>
    <scope>test</scope>
</dependency>

2. 测试

class MyStringUtil {
 
    public static String uppercase(String s) {
        return s.toUpperCase();
    }
}
 
@RunWith(PowerMockRunner.class) // 1
@PrepareForTest({ MyStringUtil.class }) // 2
public class HelloTest {
 
    @Before
    public void before() {
        PowerMockito.mockStatic(MyStringUtil.class); // 3
    }
 
    @Test
    public void test() throws IOException {
        PowerMockito.when(MyStringUtil.uppercase("abc")).thenReturn("ABC"); // 4
        assertEquals("ABC", MyStringUtil.uppercase("abc")); // 5
    }
}