如何使用try-with-resources测试方法

Question

如何对使用try-with-resources的方法进行单元测试？由于它在try子句中使用new运算符，因此无法对其进行模拟。我不想使用PowerMock。看来唯一的方法就是创建集成测试？public void methodToBeTested(File file) {    try (FileInputStream fis = new FileInputStream(file)) {        //some logic I want to test which uses fis object    } catch (Exception e) {        //print stacktrace    }}

Answer 1

您可以将依赖项实例化移动到工厂类中，并将其作为构造函数参数传递给要测试的代码。工厂类本身太简单而不会失败，因此不需要进行测试。

您是否打算做类似的事情：

try (FileInputStream fis = getCreatedFromFactory(file)) ??

– JavaIntern

几乎...

@Singleton

public class InputStreamFactory { // too simple to fail -> no UnitTests

   public InputStream createFor(File file) throws IOException, FileNotFoundException {

       retrun new FileInputStream(file);

   }

}

class UnitUnderTest {

   private final InputStreamFactory inputStreamFactory;

   UnitUnderTest(@Inject InputStreamFactory inputStreamFactory){

      this.inputStreamFactory=inputStreamFactory;

   }

   public void methodToBeTested(File file) {

        try (FileInputStream fis = inputStreamFactory.createFor(file)) {

            //some logic I want to test which uses fis object

        } catch (Exception e) {

            //print stacktrace

        }

    }

}

class UnitUnderTestTest{

   @Rule

   public MockitoRule rule = MockitoJUnit.rule();

   @Mock

   private InputStreamFactory inputStreamFactory;

   @Mock

   private InputStream inputStream;

   private final File inputFile = new File("whatever");

    // no init here, mock for inputStream not yet created

   private UnitUnderTest unitUnderTest;

   /* I don't use @InjectMocks

      since it does not cause compile error

      if constructor misses parameter */

   @Before

   public void setup() {

       unitUnderTest = new UnitUnderTest(inputStreamFactory);

       doReturn(inputStream).when(inputStreamFactory).createFor(any(File.class);

   }

   @Test

   public void createsInputStreamFromFilePassed() {

       // arrange

       /* nothing to do */

       // act

       new UnitUnderTest(inputStreamFactory).methodToBeTested(inputFile);

       // assert

       verify(inputStreamFactory).createFor(inputFile); 

       verify(inputStream).close(); 

   }

}