PowerMock不会模仿静态方法在Spring-Boot应用程序中抛出异常

Question

@Service
public class FileStorageService {
    private final Path fileStorageLocation;

    @Autowired
    public FileStorageService(final FileStorageProperties fileStorageProperties) {
            //FileStorageProperties is a very simple class that right now just holds one String value
            this.fileStorageLocation = Paths.get(fileStorageProperties.getUploadDir())
                .toAbsolutePath()
                .normalize();

        try {
            Files.createDirectories(fileStorageLocation);
        } catch (IOException e) {
            // FileStorageException is my custom, runtime exception
            throw new FileStorageException("Failed to create directory for stored files", e);
        }
    }
}

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mockito;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

import java.io.IOException;
import java.nio.file.Files;

@RunWith(PowerMockRunner.class)
@PrepareForTest({Files.class})
public class FileStorageServiceTest {
    private static final String UPLOAD_DIR = "uploadDir";

    @Test(expected = FileStorageException.class)
    public void some_test() throws IOException {
        PowerMockito.mockStatic(Files.class);
        PowerMockito.when(Files.createDirectories(Mockito.any())).thenThrow(new IOException());

        new FileStorageService(createFileStorageProperties());
    }

    private FileStorageProperties createFileStorageProperties() {
        final FileStorageProperties fileStorageProperties = new FileStorageProperties();
        fileStorageProperties.setUploadDir(UPLOAD_DIR);
        return fileStorageProperties;
    }
}

null

但是，在测试过程中没有抛出异常，并且失败。我会非常感谢你的帮助，因为我觉得我错过了一些很简单的东西，只是看不到它。

Answer 1

来自：https://github.com/powermock/powermock/wiki/mock-system

通常，您会准备包含要模拟的静态方法的类（我们称之为X)，但是因为PowerMock不可能准备系统类进行测试，所以必须采取另一种方法。因此，不准备X，而是准备调用X中静态方法的类！

基本上，我们模仿类对System类的使用，而不是不可模仿的System类本身。

@PrepareForTest({Files.class})

when(spy.doSomethingWithSystemClasses()).thenThrow(new Exception("Foo");