Java 如何使用 mockito 或 powermock 模拟局部变量

How to mock local variables using mockito or powermock

提问by ankit

I have scenario like this

我有这样的场景

InputStreamReader reader = new InputStreamReader(getFileAsStream(resourceResolver, iconpath));
                BufferedReader bReader = new BufferedReader(reader);

I have mocked till this point

我一直嘲笑到现在

getFileAsStream(resourceResolver, iconpath)

now I am getting one reader

现在我得到了一位读者

 BufferedReader bReader = new BufferedReader(reader);

but when I execute this line I get null and not able to move forward

但是当我执行这一行时，我得到空值并且无法前进

  while ((iconEntry = bReader.readLine()) != null)

Please tell me how can I mock this. Please note I cannot change my main code therefore the solution present on Mockito docs is not valid in my case

请告诉我我怎么能嘲笑这个。请注意，我无法更改我的主代码，因此 Mockito 文档中的解决方案在我的情况下无效

Test code

测试代码

@RunWith(PowerMockRunner.class)
@PrepareForTest({ FrameworkUtil.class, LoggerFactory.class })
public class IconPreviewServletTest {
    private IconPreviewServlet iconPreviewServlet;
    private SlingHttpServletRequest request;
    private SlingHttpServletResponse response;
    private Bundle bundle;
    private BundleContext bundleContext;
    private ServiceReference factoryRef;
    private CommonService resolverFactory;
    private PrintWriter out;
    private ResourceResolver resourceResolver;
    private Resource resource;
    private Node node;
    private Node jcrContent;
    private javax.jcr.Property property;
    private Binary binary;
    private InputStream stream;
    private InputStreamReader inputReader;
    private BufferedReader reader;

    @Before
    public void setUp() throws IOException, PathNotFoundException,
            RepositoryException {
        init();
    }

    private void init() throws IOException, PathNotFoundException,
            RepositoryException {

        request = mock(SlingHttpServletRequest.class);
        response = mock(SlingHttpServletResponse.class);
        bundleContext = mock(BundleContext.class);
        factoryRef = mock(ServiceReference.class);
        resolverFactory = mock(CommonService.class);
        out = mock(PrintWriter.class);
        resourceResolver = mock(ResourceResolver.class);
        resource = mock(Resource.class);
        node = mock(Node.class);
        jcrContent = mock(Node.class);
        property = mock(Property.class);
        binary = mock(Binary.class);
        stream=IOUtils.toInputStream("some test data for my input stream");



        reader = mock(BufferedReader.class);

        inputReader=mock(InputStreamReader.class);

        bundle = mock(Bundle.class);
        mockStatic(FrameworkUtil.class);
        mockStatic(LoggerFactory.class);

        Logger log = mock(Logger.class);

        when(LoggerFactory.getLogger(IconPreviewServlet.class)).thenReturn(log);
        when(FrameworkUtil.getBundle(CommonService.class)).thenReturn(bundle);
        when(bundle.getBundleContext()).thenReturn(bundleContext);
        when(bundleContext.getServiceReference(CommonService.class.getName()))
                .thenReturn(factoryRef);
        when(bundleContext.getService(factoryRef)).thenReturn(resolverFactory);
        when(request.getParameter("category")).thenReturn("category");
        when(request.getParameter("query")).thenReturn("query");
        when(response.getWriter()).thenReturn(out);
        when(request.getResourceResolver()).thenReturn(resourceResolver);
        when(
                resourceResolver
                        .getResource("/etc/designs/resmed/icons/category/icons.txt"))
                .thenReturn(resource);
        when(resource.adaptTo(Node.class)).thenReturn(node);
        when(node.getNode("jcr:content")).thenReturn(jcrContent);
        when(jcrContent.getProperty("jcr:data")).thenReturn(property);
        when(property.getBinary()).thenReturn(binary);
        when(binary.getStream()).thenReturn(stream);

    }

采纳答案by Lauri Harpf

To make this work, you need to use Powermockito to intercept the constructor calls (new InputStreamReader(...), new BufferedReader(...)) so that your mocks get returned. An example is below. In your case, just intercepting the new BufferedReader call may be enough.

为了完成这项工作，您需要使用 Powermockito 来拦截构造函数调用（new InputStreamReader(...)、new BufferedReader(...)），以便返回您的模拟。下面是一个例子。在您的情况下，只需拦截新的 BufferedReader 调用就足够了。

Assume the following is the code you want to test:

假设以下是您要测试的代码：

package test;

import java.io.*;

public class SUT {

    public String doSomething() throws IOException {
        InputStreamReader reader =
                new InputStreamReader(getFileAsStream(null, null));
        BufferedReader bReader =
                new BufferedReader(reader);

        return bReader.readLine();
    }

    private InputStream getFileAsStream(Object resourceResolver, Object iconPath)
            throws FileNotFoundException {
        return new ByteArrayInputStream("".getBytes());
    }
}

The following test code is an example of how to intercept the constructor calls:

以下测试代码是如何拦截构造函数调用的示例：

package test;

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

import java.io.BufferedReader;
import java.io.InputStreamReader;

import static org.junit.Assert.assertEquals;
import static org.powermock.api.mockito.PowerMockito.doReturn;
import static org.powermock.api.mockito.PowerMockito.mock;

@RunWith(PowerMockRunner.class)
@PrepareForTest({ SUT.class })
public class SUTTest {

    @Test
    public void doSomethingReturnsValueFromBufferedReader() throws Exception {
        // Arrange
        SUT sut = new SUT();
        InputStreamReader inputStreamReaderMock = mock(InputStreamReader.class);
        BufferedReader bufferedReaderMock = mock(BufferedReader.class);

        // Set your mocks up to be returned when the new ...Reader calls 
        // are executed in sut.doSomething()
        PowerMockito.whenNew(InputStreamReader.class).
                     withAnyArguments().thenReturn(inputStreamReaderMock);
        PowerMockito.whenNew(BufferedReader.class).
                     withArguments(inputStreamReaderMock).
                     thenReturn(bufferedReaderMock);

        // Set the value you want bReader.readLine() to return 
        // when sut.doSomething() executes
        final String bufferedReaderReturnValue = "myValue";
        doReturn(bufferedReaderReturnValue).when(bufferedReaderMock).readLine();

        // Act
        String result = sut.doSomething();

        // Assert
        assertEquals(bufferedReaderReturnValue, result);
    }
}

This hopefully helps you in your immediate problem. However, it seems to me that what you're creating will be a very slow, confusing and brittle test. Right now, you're mocking so much that it makes very hard to determine what you're actually trying to test.

这有望帮助您解决当前的问题。然而，在我看来，您正在创建的将是一个非常缓慢、混乱和脆弱的测试。现在，您的嘲弄太多了，以至于很难确定您实际要测试的内容。

The high amount of mocking probably indicates that the design of the code you're testing would need some work to improve testability. If you can't touch the code, then you can't - but try to make your test more readable and intuitive ("When this method is invoked, this thing should happen, because...").

大量的模拟可能表明您正在测试的代码设计需要一些工作来提高可测试性。如果您不能触摸代码，那么您就不能 - 但尝试使您的测试更具可读性和直观性（“当调用此方法时，这件事应该发生，因为......”）。

回答by Tien Nguyen

to make this line work:

使这条线工作：

 while ((iconEntry = bReader.readLine()) != null)

you must determine how many lines you want to read and add this to your test code:

您必须确定要读取的行数并将其添加到测试代码中：

when(bReader.readLine()).thenReturn("line number one").thenReturn("line number two");