PowerMock没有正确模拟

Question

我已经编写了一个简单的方法，该方法应该获取一个url，并通过get请求从该url中检索数据。方法如下：

public String getResponse(String connectionUrl) throws HttpException {
    HttpURLConnection connection = null;
    try {
        URL url = new URL(connectionUrl);
        connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");
        int responseCode = connection.getResponseCode();
        if (responseCode != 200) {
            throw new HttpException("Response code was " + responseCode + " (should be 200)");
        }
        Scanner scanner = new Scanner(connection.getInputStream()).useDelimiter("\A");
        String response = scanner.hasNext() ? scanner.next() : "";
        connection.disconnect();
        scanner.close();
        return response;
    } catch (IOException e) {
        if (connection != null) {
            connection.disconnect();
        }
        throw new HttpException(e.getMessage(), e.getCause());
    }
}

现在我正在为这个方法编写单元测试。我将PowerMock与Mockito和JUnit一起用于编写测试。有问题的测试如下：

@Test
public void getResponse_NormalResponse() throws Exception {
    String expectedResponse = "This is the expected response text!";
    URL url = PowerMockito.mock(URL.class);
    HttpURLConnection connection = PowerMockito.mock(HttpURLConnection.class);
    InputStream inputStream = PowerMockito.mock(InputStream.class);
    Scanner scanner = PowerMockito.mock(Scanner.class);
    PowerMockito.whenNew(URL.class).withArguments(REQUEST_URL).thenReturn(url);
    PowerMockito.whenNew(Scanner.class).withArguments(inputStream).thenReturn(scanner);
    PowerMockito.when(url.openConnection()).thenReturn(connection);
    // Response code mocked here
    PowerMockito.when(connection.getResponseCode()).thenReturn(200); 
    PowerMockito.when(connection.getInputStream()).thenReturn(inputStream);
    PowerMockito.when(scanner.hasNext()).thenReturn(true);
    PowerMockito.when(scanner.next()).thenReturn(expectedResponse);
    HttpClient httpClient = new HttpClient();
    String actualResponse = httpClient.getResponse(REQUEST_URL);
    Assert.assertEquals("Response is wrong!", expectedResponse, actualResponse);
}

但是当我运行测试时，会抛出一个HttpException，因为响应代码是404。测试使用PowerMockRunner运行。我做错了什么，为什么这个测试不能正常工作？

Answer 1

由于您使用的是whenNew，因此您还必须添加在@PrepareForTest下创建新对象的类。

您的类似乎是HttpClient

@PrepareForTest({ URL.class, Scanner.class ,HttpClient.class})

解决了测试中的另一个问题。添加了缺失的期望值。

PowerMockito.when(scanner.useDelimiter("\A")).thenReturn(scanner);

修正后的工作代码：

来源：

public class HttpClient {
    public String getResponse(String connectionUrl) throws HttpException {
        HttpURLConnection connection = null;
        try {
            URL url = new URL(connectionUrl);
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            int responseCode = connection.getResponseCode();
            if (responseCode != 200) {
                throw new HttpException("Response code was " + responseCode
                        + " (should be 200)");
            }
            Scanner scanner = new Scanner(connection.getInputStream())
                    .useDelimiter("\A");
            String response = scanner.hasNext() ? scanner.next() : "";
            connection.disconnect();
            scanner.close();
            return response;
        } catch (IOException e) {
            if (connection != null) {
                connection.disconnect();
            }
            throw new HttpException(e.getMessage(), e.getCause());
        }
    }
}
class HttpException extends Exception {
    public HttpException(String string) {
        super(string);
    }
    public HttpException(String message, Throwable cause) {
        super(message, cause);
    }
}

测试用例：

@RunWith(PowerMockRunner.class)
@PrepareForTest({ URL.class, Scanner.class, HttpClient.class })
public class HttpClientTest {
    private static final String REQUEST_URL = "http://wwww.google.com";
    @Test
    public void getResponse_NormalResponse() throws Exception {
        String expectedResponse = "This is the expected response text!";
        URL url = PowerMockito.mock(URL.class);
        HttpURLConnection connection = PowerMockito
                .mock(HttpURLConnection.class);
        InputStream inputStream = PowerMockito.mock(InputStream.class);
        Scanner scanner = PowerMockito.mock(Scanner.class);
        PowerMockito.whenNew(URL.class).withArguments(REQUEST_URL)
                .thenReturn(url);
        PowerMockito.whenNew(Scanner.class).withArguments(inputStream)
                .thenReturn(scanner);
        PowerMockito.when(scanner.useDelimiter("\A")).thenReturn(scanner);
        PowerMockito.when(url.openConnection()).thenReturn(connection);
        // Response code mocked here
        PowerMockito.when(connection.getResponseCode()).thenReturn(200);
        PowerMockito.when(connection.getInputStream()).thenReturn(inputStream);
        PowerMockito.when(scanner.hasNext()).thenReturn(true);
        PowerMockito.when(scanner.next()).thenReturn(expectedResponse);
        HttpClient httpClient = new HttpClient();
        String actualResponse = httpClient.getResponse(REQUEST_URL);
        Assert.assertEquals("Response is wrong!", expectedResponse,
                actualResponse);
    }
}

附上我用过的pom。

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>MockItToExample</groupId>
    <artifactId>MockItToExample</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>org.mockito</groupId>
            <artifactId>mockito-all</artifactId>
            <version>1.10.19</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/junit/junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <dependency>
            <groupId>org.powermock</groupId>
            <artifactId>powermock-module-junit4</artifactId>
            <version>1.6.3</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.powermock</groupId>
            <artifactId>powermock-api-mockito</artifactId>
            <version>1.6.3</version>
        </dependency>
    </dependencies>
    <build>
        <sourceDirectory>src</sourceDirectory>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>1.7</source>
                    <target>1.7</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Answer 2

用注释测试类

@PrepareForTest({URL.class, Scanner.class})

当您想要模拟对象创建时，您需要为每种情况添加它(对于使用whenNew的每个类(。