how to mock a URL connection

Question

Hi I have a method that takes an URL as an input and determines if it is reachable. Heres the code for that:

public static boolean isUrlAccessible(final String urlToValidate) throws WAGNetworkException {
        URL url = null;
        HttpURLConnection huc = null;
        int responseCode = -1;
        try {
            url = new URL(urlToValidate);
            huc = (HttpURLConnection) url.openConnection();
            huc.setRequestMethod("HEAD");
            huc.connect();
            responseCode = huc.getResponseCode();
        } catch (final UnknownHostException e) {
            throw new WAGNetworkException(WAGConstants.INTERNET_CONNECTION_EXCEPTION);
        } catch (IOException e) {
            throw new WAGNetworkException(WAGConstants.INVALID_URL_EXCEPTION);
        } finally {
            if (huc != null) {
                huc.disconnect();
            }
        }
        return responseCode == 200;
    }

I want to unit test the isUrlAccessible() method using PowerMockito. I feel that I will need to use whenNew() to mock the creation of URL and the when url.openConnection() is called, return another mock HttpURLConnection object. But I have am not sure how to implement this? Am I on the right track? Can anyone help me in implementing this?

For what it's worth, I would suggest you take a good hard look at JMockit (jmockit.github.io) and then see if you can turn away from it--I could not and it's been my go to mocking framework ever since. — unigeek, Aug 16 '14 at 03:15

Nemin · Accepted Answer · 2014-08-16T01:42:12.537

13

Found the solution. First mock the URL class, then Mock the HttpURLConnection and when url.openconnection() is called, return this mocked HttpURLConnection object and finally set its response code to 200. Heres the code:

@Test
    public void function() throws Exception{
        RuleEngineUtil r = new RuleEngineUtil();
        URL u = PowerMockito.mock(URL.class);
        String url = "http://www.sdsgle.com";
        PowerMockito.whenNew(URL.class).withArguments(url).thenReturn(u);
        HttpURLConnection huc = PowerMockito.mock(HttpURLConnection.class);
        PowerMockito.when(u.openConnection()).thenReturn(huc);
        PowerMockito.when(huc.getResponseCode()).thenReturn(200);
        assertTrue(r.isUrlAccessible(url));

    }

edited Aug 16 '14 at 01:42

answered Aug 15 '14 at 21:49

Nemin

1,907
6
24
37

11

Does this work, it gives me an error at line ``PowerMockito.when(u.openConnection()).thenReturn(huc);``, saying AbstractMethodError. – rd22 Nov 30 '15 at 12:11
does not work for me either... I get: java.net.MalformedURLException: no protocol – Hamid Apr 01 '16 at 21:02
2

For mocking URL, you should also consider adding @PrepareForTest({URL.class, }) as per http://vaguehope.com/2012/02/powermock-puzzler/ – Bhaskar Apr 17 '18 at 01:50
1

For anyone else who gets an AbstractMethodError in the future, I think the solution may be changing your @Test import from org.junit.jupiter.api.Test to org.junit.Test. – P123 Aug 10 '21 at 23:11

score 5 · Answer 2 · answered Aug 15 '14 at 21:17

5

You can mock new Url instance with

whenNew(URL.class)..

Make sure you return a previously created mock object from that whenNew call.

URL mockUrl = Mockito.mock(URL.class);
whenNew(URL.class).....thenReturn(mockUrl );

Then you can add behavior to your mock as you want.

answered Aug 15 '14 at 21:17

Sezin Karli

2,517
19
24

2

we cant mock a final class (URL) – Don Jose Jul 18 '19 at 06:56
@doN, Powermockito can mock a final class (URL). – user674669 Apr 14 '20 at 20:45

minhaz · Answer 3 · 2019-06-20T01:36:45.857

Although this thread has some good suggestion, but if any of you is not interested to use those third-party libraries here is a quick solution.

public class MockHttpURLConnection extends HttpURLConnection {
    private int responseCode;
    private URL url;
    private InputStream inputStream;


    public MockHttpURLConnection(URL u){
        super(null);
        this.url=u;
    }
    @Override
    public int getResponseCode() {
        return responseCode;
    }


    public void setResponseCode(int responseCode) {
        this.responseCode = responseCode;
    }

    @Override
    public URL getURL() {
        return url;
    }

    public void setUrl(URL url) {
        this.url = url;
    }

    @Override
    public InputStream getInputStream() {
        return inputStream;
    }

    public void setInputStream(InputStream inputStream) {
        this.inputStream = inputStream;
    }

    @Override
    public void disconnect() {

    }

    @Override
    public boolean usingProxy() {
        return false;
    }

    @Override
    public void connect() throws IOException {

    }
}

And, this how you can set the desired behaviour

   MockHttpURLConnection httpURLConnection=new MockHttpURLConnection(new URL("my_fancy_url"));
        InputStream stream=new ByteArrayInputStream(json_response.getBytes());
        httpURLConnection.setInputStream(stream);
        httpURLConnection.setResponseCode(200);

Note: It just mock 3 methods from HttpUrlConnection and if you are using more method you need to make sure those are mock as well.

Pranab Thakuria · Answer 4 · 2019-04-01T09:58:05.790

URL is final class. To mock final class we can use PowerMockito with Junit. To mock final class we need to annotate Test class with @RunWith(PowerMockRunner.class) and @PrepareForTest({ URL.class })


@RunWith(PowerMockRunner.class) 
@PrepareForTest({ URL.class })
public class Test {
    @Test
    public void test() throws Exception {
        URL url = PowerMockito.mock(URL.class);
        HttpURLConnection huc = Mockito.mock(HttpURLConnection.class);
        PowerMockito.when(url.openConnection()).thenReturn(huc);
        assertTrue(url.openConnection() instanceof HttpURLConnection);
    }
}

But in the line PowerMockito.when(url.openConnection()).thenReturn(huc); following error is thrown:

java.lang.AbstractMethodError
    at java.net.URL.openConnection(URL.java:971)
    at java_net_URL$openConnection.call(Unknown Source)

In order to get rid of this error we can modify our Test class as shown below:

@RunWith(PowerMockRunner.class) 
@PrepareForTest({ URL.class })
public class Test {
    @Test
    public void test() throws Exception {

        public class UrlWrapper {

            URL url;

            public UrlWrapper(String spec) throws MalformedURLException {
                url = new URL(spec);
            }

            public URLConnection openConnection() throws IOException {
                return url.openConnection();
            }
        }

        UrlWrapper url = Mockito.mock(UrlWrapper.class);
        HttpURLConnection huc = Mockito.mock(HttpURLConnection.class);
        PowerMockito.when(url.openConnection()).thenReturn(huc);
        assertTrue(url.openConnection() instanceof HttpURLConnection);
    }
}

Visit: https://programmingproblemsandsolutions.blogspot.com/2019/04/abstractmethoderror-is-thrown-on.html

score 0 · Answer 5 · answered Oct 23 '18 at 20:56

In order to mock java.net.URL class through mockito library, you need to perform the following steps:

Create a directory, named 'mockito-extensions' in src/tests/resources directory.
Create text a text file in the folder, named org.mockito.plugins.MockMaker and put mock-maker-inline text into the file.
you can mock the class like the following:

code:

package myproject;

import org.junit.Test;

import java.net.HttpURLConnection;
import java.net.URL;
import static org.junit.Assert.*;
import static org.mockito.Mockito.*;

public class Test {
    @Test
    public void test() throws Exception {
        URL url = mock(URL.class);
        HttpURLConnection huc = mock(HttpURLConnection.class);
        when(url.openConnection()).thenReturn(huc);
        assertTrue(url.openConnection() instanceof HttpURLConnection);
    }
}

score 0 · Answer 6 · answered May 23 '19 at 02:55

It's much simpler with the JMockit mocking API (and even simpler with no mocking):

import java.io.*;
import java.net.*;
import org.junit.*;
import static org.junit.Assert.*;
import mockit.*;

public final class ExampleURLTest {
   public static final class ClassUnderTest {
      public static boolean isUrlAccessible(String urlToValidate) throws IOException {
         HttpURLConnection huc = null;
         int responseCode;

         try {
            URL url = new URL(urlToValidate);
            huc = (HttpURLConnection) url.openConnection();
            huc.setRequestMethod("HEAD");
            huc.connect();
            responseCode = huc.getResponseCode();
         }
         finally {
            if (huc != null) {
               huc.disconnect();
            }
         }

         return responseCode == 200;
      }
   }

   // Proper tests, no unnecessary mocking ///////////////////////////////////////

   @Test
   public void checkAccessibleUrl() throws Exception {
      boolean accessible = ClassUnderTest.isUrlAccessible("http://google.com");

      assertTrue(accessible);
   }

   @Test(expected = UnknownHostException.class)
   public void checkInaccessibleUrl() throws Exception {
      ClassUnderTest.isUrlAccessible("http://inaccessible12345.com");
   }

   @Test
   public void checkUrlWhichReturnsUnexpectedResponseCode(
      @Mocked URL anyURL, @Mocked HttpURLConnection mockConn
   ) throws Exception {
      new Expectations() {{ mockConn.getResponseCode(); result = -1; }};

      boolean accessible = ClassUnderTest.isUrlAccessible("http://invalidResource.com");

      assertFalse(accessible);
   }

   // Lame tests with unnecessary mocking ////////////////////////////////////////

   @Test
   public void checkAccessibleUrl_withUnnecessaryMocking(
      @Mocked URL anyURL, @Mocked HttpURLConnection mockConn
   ) throws Exception {
      new Expectations() {{ mockConn.getResponseCode(); result = 200; }};

      boolean accessible = ClassUnderTest.isUrlAccessible("http://google.com");

      assertTrue(accessible);
   }

   @Test(expected = UnknownHostException.class)
   public void checkInaccessibleUrl_withUnnecessaryMocking(
      @Mocked URL anyURL, @Mocked HttpURLConnection mockConn
   ) throws Exception {
      new Expectations() {{ mockConn.connect(); result = new UnknownHostException(); }};

      ClassUnderTest.isUrlAccessible("http://inaccessible12345.com");
   }
}

(Verified with JMockit 1.47 on JDKs 8 & 9.)

jumping_monkey · Answer 7 · 2021-08-19T07:07:59.637

You need to configure Mockito before it can be used to mock final classes and methods. (Tested with JUnit 5 & mockito-core-3.6.28)

Steps:

Create a directory named src/test/resources/mockito-extensions
Inside it, create a file named org.mockito.plugins.MockMaker
Add a single line inside the file, mock-maker-inline

Now, you can mock your final class, example:

URL url = Mockito.mock(URL.class)

Note: As per this issue, PowerMock does not work with JUnit 5.

how to mock a URL connection

7 Answers7

Steps:

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