Java如何Mock FileInputStream问题

public class Class1 {
    public Class1() { }
    public boolean method1() {
        try {
            FileInputStream fileInputStream = new FileInputStream("file.txt");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }
}

@RunWith(PowerMockRunner.class)
@PrepareForTest(Class1.class)
public class Class1Test {
    @Test
    public void method1Test() throws Exception {
        Class1 class1 = new Class1();
        FileInputStream fileInputStreamMock = mock(FileInputStream.class);
        whenNew(FileInputStream.class).withAnyArguments().thenReturn(fileInputStreamMock);
        boolean expected = true;
        boolean actual = class1.method1();
        assertEquals(expected, actual);
    }
}

@RunWith(PowerMockRunner.class)
@PrepareForTest(Class1.class)
public class Class1Test {
    @Test
    public void method1Test() throws Exception {
        Class1 class1 = new Class1();
        String path = new File(getClass().getClassLoader().getResource("file.txt").getFile()).getCanonicalPath();
        FileInputStream fileInputStream = new FileInputStream(path);
        whenNew(FileInputStream.class).withAnyArguments().thenReturn(fileInputStreamMock);
        boolean expected = true;
        boolean actual = class1.method1();
        assertEquals(expected, actual);
    }
}

<dependency>
        <groupId>org.powermock</groupId>
        <artifactId>powermock-module-junit4</artifactId>
        <version>1.7.4</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.powermock</groupId>
        <artifactId>powermock-api-mockito</artifactId>
        <version>1.7.4</version>
        <scope>test</scope>
    </dependency>
</dependencies>

Process mockProcess = mock(Process.class);
InputStream errorStream = org.apache.commons.io.IOUtils.toInputStream("error message", "UTF-8");
when(mockProcess.getErrorStream()).thenReturn(errorStream);