We Keep Coding

Mockito mocking a new instance call with parameters

For school purposes I am creating an application that's working with a stock API.
I am trying to write a test for a method that gets all the stock data of the last 10 years. Instead of actually getting all that data, I want to throw an exception.
The method I Want to test:
#Override
public List<StockData> getAllTeslaStockData() throws AlphaVantageException {
List<StockData> stockData;
AlphaVantageConnector apiConnector = new AlphaVantageConnector(APIKEY, TIMEOUT);
TimeSeries stockTimeSeries = new TimeSeries(apiConnector);
try {
Daily responseDaily = stockTimeSeries.daily("TSLA", OutputSize.FULL);
stockData = responseDaily.getStockData();
} catch (AlphaVantageException e) {
LOGGER.log(Level.SEVERE, "something went wrong: ", e);
throw e;
}
return stockData;
}
The stockTimeSeries.daily(....) call can throw the AlphaVantageException.
I've mocked the TimeSeries class like this:
TimeSeries stockTimeSeries = mock(TimeSeries.class);
In my test class I want to mock this call, and return an exception instead of actual data.
when(stockTimeSeries.daily("TSLA", OutputSize.FULL)).thenThrow(new AlphaVantageException("No stock data available"));
Regardless of how I am trying to mock this bit of code, it'll never throw the exception. It will always just execute the code, and return valid stock data, instead of throwing the exception like i've tried to do.
How can I mock this bit of code, so that itll throw the exception I am expecting for my tests.
The AlphaVantageConnector, TimeSeries and Daily classes are part of a library used to access the stock API, so I can't change these classes.
I am using JUnit 4.12 and Mockito to try and achieve this.

You can use thenThrow() method. Below is the example
#Test(expected = NullPointerException.class)
public void whenConfigNonVoidRetunMethodToThrowEx_thenExIsThrown() {
MyDictionary dictMock = mock(MyDictionary.class);
when(dictMock.getMeaning(anyString()))
.thenThrow(NullPointerException.class);
dictMock.getMeaning("word");

The TimeSeries object is created in the method itself, so you can't mock it - mocking is intended to mock members.
What you can do is to do something like
class YourClass {
private Supplier<TimeSeries> seriesCreator = () -> {
return new TimeSeries(new AlphaVantageConnector(APIKEY, TIMEOUT));
}
which you use to create the series in your method
#Override
public List<StockData> getAllTeslaStockData() throws AlphaVantageException {
TimeSeries stockTimeSeries = seriesCreator.get();
Now you can mock that Supplier.
#Mock Supplier<TimeSeries> seriesCreatorMock;
#InjectMocks MyClass sut;
and in your test
#Test(expected = AlphaVantageException.class)
void testException() {
when(seriesCreatorMock.get()).thenThrow(new AlphaVantageException());
sut.getAllTeslaStockData()
}
EDIT: as suggested by Angkur in the comments, the clean way would be to
class SeriesCreator implements Supplier<TimeSeries> {
public TimeSeries get() {
return new TimeSeries(new AlphaVantageConnector(APIKEY, TIMEOUT));
}
}
class YourClass {
private Supplier<TimeSeries> seriesCreator = new SeriesCreator();
// ...

The code in the main class is creating a new instance of TimeSeries which it will use every time this method is called, so the mocked TimeSeries object is not getting used at all.
TimeSeries stockTimeSeries = new TimeSeries(apiConnector); // --> This is not getting mocked
try {
Daily responseDaily = stockTimeSeries.daily("TSLA", OutputSize.FULL);
stockData = responseDaily.getStockData();
}
You should create another method in your class (or even a separate class if it better satisfies the SOLID principles) which returns you the TimeSeries object. Something like:-
<access modifier> TimeSeries getTimeSeries(...) {
}
and then this method should be mocked in the Junit, and when mocked, it should return the Mocked TimeSeries reference (which is created in TimeSeries stockTimeSeries = mock(TimeSeries.class); ). You would need to use .spy() on the main class (unless you are using a different class to create TimeSeries object) in order to be able to mock the specific method getTimeSeries() but not the others.
MainClass mainObject = Mockito.spy(new MainClass());
Mockito.when(mainObject.getTimeSeries()).thenReturn(stockTimeSeries);
Then, the method call stockTimeSeries.daily() will get actually mocked by your existing code :
when(stockTimeSeries.daily("TSLA", OutputSize.FULL)).thenThrow(new AlphaVantageException("No stock data available"));
NOTE: you should also consider using .anyString() style methods provided by Mockito API while mocking.

How to mock StreamingOutput from jax-rs

I have a class which send video as mp4 file to user (Http request/response)
I want to Mock method with main logic to test it. My code
public StreamingOutput videoAsStream(final String videoUrl) {
try {
final URL url = new URL(videoUrl);
return output -> {
try(final InputStream inputStream = url.openConnection().getInputStream()){
IOUtils.copy(inputStream,output);
output.close();
}
};
} catch (final MalformedURLException e) {
log.error("Url exception for url {}",videoUrl);
throw new UncheckedIOException(e);
}
}
What is my way to mock this logic?

The problem is, that URL is final, so you will have to use at least Mockito 2 to mock it. If you are ready to do that, I see two possibilities:
a) Give the url into the method and not the string, thus allowing you to put a mocked url in there. That would be the most simply method. You could also then create a 2nd convenience method that creates said URL from a string. Those two methods will be easier to test because their scope is smaller.
b) Extract the final URL url = new URL(videoUrl); part into a new class, for example a URL Factory, then mock that to return a mocked URL object in your test.
As soon as you produce stuff with "new" inside your method, this method can become harder to test, because you now cannot separate this test from this object generation.

AFAIK, you can't mock final and static methods/classes using mockito. you would have to depend on PowerMockito. I am currently not able to test your method but if you want to mock final/static, you can do as
first, Add the final/static classes to #PrepareForTest then
InputStream mockInputStream = Mockito.mock(InputStream.class);
OutputStream mockOutputStream = Mockito.mock(OutputStream.class);
PowerMockito.mockStatic(IOUtils.class);
Mockito.when(IOUtils.copy(mockInputStream, mockOutputStream)).thenReturn(1L);
Mockito.doNothing().when(mockOutputStream).close();
Let me know if this does not work for you.

Mocking objects for JUnit test

I'm writing a Junit to test the following method in Client.java:
public FSDataInputStream getObj(String hName, Path p) throws IOException {
String myKey = pathToKey(hName, p);
FileStatus status = memoryCache.getStatus(p.toString());
if (status == null) {
status = getStatus(hName, p, "getObject");
}
if (status.isDirectory()) {
throw new FileNotFoundException("Can't open " + path
+ " because it is a directory");
}
InputStream inputStream = new InputStream(bucket, myKey,
status.getLen(), client, readAhead, inputPolicy);
return new FSDataInputStream(inputStream);
}
Initially I want to test if status == null then getStatus() is invoked and if status.isDirectory(), the FileNotFoundException is thrown
I'm new to Junit so not completely sure what I'm at but to the best of my knowledge I think I need to mock the following:
List item
Client
status
inputStream
possibly memoryCache
So far this is what I've got:
#Before
public final void before() {
private COSAPIClient myClient;
private String myBucket;
FileStatus myStatus;
InputStream myInputStream;
myClient = PowerMockito.mock(AmazonS3.class);
myInputStream = PowerMockito.mock(InputStream.class);
myFileStatus = PowerMockito.mock(FileStatus.class);
}
#Test
public void getObjTest() throws Exception {
URI uri = new URI("xyz://aa-bb-cc/data7-1-23-a.txt");
String hName = "xyz://aa-bb-cc/";
Path p = new Path("cos://aa-bb-cc/data7-1-23-a.txt");
Configuration conf = new Configuration();
myClient = spy(new Client(uri, conf));
myStatus = spy(new FileStatus());
myMemoryCache.getStatus(p.toString());
InputStream = spy(new InputStream(myBucket, objectKey, 300, myClient, 12345678910L, myInputPolicy));
}
It returns a NullPointerError at this line in my program:
FileStatus status = memoryCache.getStatus(p.toString());
I wonder is anybody could advice if/what I'm doing wronfg and how I should go about resolving this?

First, the real answer: step back for a moment. Don't start with JUnit and Mockito and your production code as input. Rather have a look into a tutorial (like here) that step-by-step explains all the relevant elements and how to "bring" them together.
In your case, the are various problems with your code:
Why are you using PowerMock? Try to go with "plain vanilla" Mockito. If your production code is so that it requires PowerMock, rather consider to rework your production instead of turning to PowerMock.
You seem to really not know where/how to apply mocking. In other words: you only mock the elements that you need to control when running your code under test. And you only use mocking, if you can't control them otherwise. Meaning: you almost never mock a list - you simply create a "normal" list to then add the things that this list should contain.
Creating a mock allows to invoke methods on that mock object. But by default, any method that returns something will return null (or maybe an empty collection, or 0 for primitive return types, see here for details). Thus you rather need a statement such as when(mockedCache.getStatus("some string")).thenReturn(someResult).

How to write a jUnit test for a class that uses a network connection

I would like to know what's the best approach to test the method "pushEvent()" in the following class with a jUnit test.
My problem is, that the private method "callWebsite()" always requires a connection to the network. How can I avoid this requirement or refactor my class that I can test it without a connection to the network?
class MyClass {
public String pushEvent (Event event) {
//do something here
String url = constructURL (event); //construct the website url
String response = callWebsite (url);
return response;
}
private String callWebsite (String url) {
try {
URL requestURL = new URL (url);
HttpURLConnection connection = null;
connection = (HttpURLConnection) requestURL.openConnection ();
String responseMessage = responseParser.getResponseMessage (connection);
return responseMessage;
} catch (MalformedURLException e) {
e.printStackTrace ();
return e.getMessage ();
} catch (IOException e) {
e.printStackTrace ();
return e.getMessage ();
}
}
}

Stubbing
You'll need a test double (stub) to allow isolated, easy, unit testing. The following is non tested, but demonstrates the idea. The use of Dependency Injection will allow you to inject at test time, a test version of your HttpURLConnection.
public class MyClass()
{
private IHttpURLConnection httpUrlConnection;
public MyClass(IHttpURLConnection httpUrlConnection)
{
this.httpUrlConnection = httpUrlConnection;
}
public String pushEvent(Event event)
{
String url = constructURL(event);
String response = callWebsite(url);
return response;
}
}
Then you create a stub (sometimes referred to as a mock object) to be the stand in for the concrete instance.
class TestHttpURLConnection : IHttpURLConnection { /* Methods */ }
You'll also construct a concrete version, for your production code to use.
class MyHttpURLConnection : IHttpURLConnection { /* Methods */ }
Using your test class (an adapter) you are able to specifiy what should happen during your test. A mocking framework will enable you to do this with less code, or you can manually wire this up. The end result of this for your test is that you'll set your expectations for your test, for example, in this case you may set OpenConnection to return a true boolean (This is just an example by the way). Your test will then assert that when this value is true, the return value of your PushEvent method matches some expected result. I've not touched Java properly for a while, but here are some recommended mocking frameworks as specified by StackOverflow members.

Possible solution: You can extend this class, override callWebsite (you have to make it protected for this purpose) - and the override method write some stub method implementation.

Approaching things from a slightly different angle...
I'd worry less about testing this specific class. The code in it is extremely simple and, while a functional test to make sure it's working with a connection would be helpful, a unit level test "may" not be necessary.
Instead, I'd focus on testing the methods it calls that appear to actually do something. Specifically...
I'd test constructURL method from this line:
String url = constructURL (event);
making sure that it can construct a URL properly from different Events, and throws Exceptions when it should (possibly on an invalid Event or null).
And I'd test the method from the following line:
String responseMessage = responseParser.getResponseMessage (connection);
Possibly pulling out any "get information out of the connection" logic into one proc, and leaving only "parse said information" in the original one:
String responseMessage = responseParser.getResponseMessage(responseParser.getResponseFromConnection(connection));
or something along those lines.
The idea being to put any "must deal with external data sources" code in one method, and any code logic in separate methods that can be easily tested.

As an alternative to Finglas's helpful answer with respect to mocking, consider a stubbed approach where we override the functionality of callWebsite(). This works quite well in the case where we aren't so interested in the logic of callWebsite as that of the other logic called within pushEvent(). One important thing to check is that callWebsite is calledwith the correct URL. So, first change is to the method signature of callWebsite() to become:
protected String callWebsite(String url){...}
Now we create a stubbed class like this:
class MyClassStub extends MyClass {
private String callWebsiteUrl;
public static final String RESPONSE = "Response from callWebsite()";
protected String callWebsite(String url) {
//don't actually call the website, just hold onto the url it was going to use
callWebsiteUrl = url;
return RESPONSE;
}
public String getCallWebsiteUrl() {
return callWebsiteUrl;
}
}
And finally in our JUnit test:
public class MyClassTest extends TestCase {
private MyClass classUnderTest;
protected void setUp() {
classUnderTest = new MyClassStub();
}
public void testPushEvent() { //could do with a more descriptive name
//create some Event object 'event' here
String response = classUnderTest.pushEvent(event);
//possibly have other assertions here
assertEquals("http://some.url",
(MyClassStub)classUnderTest.getCallWebsiteUrl());
//finally, check that the response from the callWebsite() hasn't been
//modified before being returned back from pushEvent()
assertEquals(MyClassStub.RESPONSE, response);
}
}

Create an abstract class WebsiteCaller which would be a parent of ConcreteWebsiteCaller and WebsiteCallerStub.
This class should have one method callWebsite (String url). Move your callWebsite method from MyClass to ConcreteWebsiteCaller. And MyClass will look like:
class MyClass {
private WebsiteCaller caller;
public MyClass (WebsiteCaller caller) {
this.caller = caller;
}
public String pushEvent (Event event) {
//do something here
String url = constructURL (event); //construct the website url
String response = caller.callWebsite (url);
return response;
}
}
and implement method callWebsite in your WebsiteCallerStub in some way appropriate for testing.
Then in your unit test do something like this:
#Test
public void testPushEvent() {
MyClass mc = new MyClass (new WebsiteCallerStub());
mc.pushEvent (new Event(...));
}

How do I create a mock object for Spring's WebServiceTemplate?

I have a class which calls out to an existing web service. My class properly handles valid results as well as fault strings generated by the web service. The basic call to the web service looks something like this (although this is simplified).
public String callWebService(final String inputXml)
{
String result = null;
try
{
StreamSource input = new StreamSource(new StringReader(inputXml));
StringWriter output = new StringWriter();
_webServiceTemplate.sendSourceAndReceiveToResult(_serviceUri, input, new StreamResult(output));
result = output.toString();
}
catch (SoapFaultClientException ex)
{
result = ex.getFaultStringOrReason();
}
return result;
}
Now I need to create some unit tests which test all of the success and failure conditions. It cannot call the actual web service, so I was hoping there were mock objects available for the client side of Spring-WS. Does anyone know of an mock objects available for the WebServiceTemplate or any related classes? Should I just attempt to write my own and modify my class to use the WebServiceOperations interface vs. WebServiceTemplate?

Michael's answer is very close, but here is the example that works.
I already use Mockito for my unit tests, so I am familiar with the library. However, unlike my previous experience with Mockito, simply mocking the return result does not help. I need to do two things to test all of the use cases:
Modify the value stored in the StreamResult.
Throw a SoapFaultClientException.
First, I needed to realize that I cannot mock WebServiceTemplate with Mockito since it is a concrete class (you need to use EasyMock if this is essential). Luckily, the call to the web service, sendSourceAndReceiveToResult, is part of the WebServiceOperations interface. This required a change to my code to expect a WebServiceOperations vs a WebServiceTemplate.
The following code supports the first use case where a result is returned in the StreamResult parameter:
private WebServiceOperations getMockWebServiceOperations(final String resultXml)
{
WebServiceOperations mockObj = Mockito.mock(WebServiceOperations.class);
doAnswer(new Answer()
{
public Object answer(InvocationOnMock invocation)
{
try
{
Object[] args = invocation.getArguments();
StreamResult result = (StreamResult)args[2];
Writer output = result.getWriter();
output.write(resultXml);
}
catch (IOException e)
{
e.printStackTrace();
}
return null;
}
}).when(mockObj).sendSourceAndReceiveToResult(anyString(), any(StreamSource.class), any(StreamResult.class));
return mockObj;
}
The support for the second use case is similar, but requires the throwing of an exception. The following code creates a SoapFaultClientException which contains the faultString. The faultCode is used by the code I am testing which handles the web service request:
private WebServiceOperations getMockWebServiceOperations(final String faultString)
{
WebServiceOperations mockObj = Mockito.mock(WebServiceOperations.class);
SoapFault soapFault = Mockito.mock(SoapFault.class);
when(soapFault.getFaultStringOrReason()).thenReturn(faultString);
SoapBody soapBody = Mockito.mock(SoapBody.class);
when(soapBody.getFault()).thenReturn(soapFault);
SoapMessage soapMsg = Mockito.mock(SoapMessage.class);
when(soapMsg.getSoapBody()).thenReturn(soapBody);
doThrow(new SoapFaultClientException(soapMsg)).when(mockObj).sendSourceAndReceiveToResult(anyString(), any(StreamSource.class), any(StreamResult.class));
return mockObj;
}
More code may be required for both of these use cases, but they work for my purposes.

actually i don't know if there exist preconfigured Mock Objects, but i doubt there are configured for all your "failure Conditions", so you can create a special Spring ApplicationContext for your JUnit Test with a substitute or work with a mock Framework, it's not that hard :-)
i used the Mockito Mock Framework for the example (and typed it quickly), but EasyMock or your preferred mock framework should do it as well
package org.foo.bar
import java.util.ArrayList;
import java.util.List;
import org.junit.Before;
import org.junit.Test;
import static org.mockito.Mockito.*;
import static org.junit.Assert.*;
public class WebserviceTemplateMockTest {
private WhateverTheInterfaceIs webServiceTemplate;
private TestClassInterface testClass;
private final String inputXml = "bar";
#Test
public void testClient(){
//
assertTrue("foo".equals(testClass.callWebService(inputXml));
}
/**
* Create Webservice Mock.
*/
#Before
public void createMock() {
// create Mock
webServiceTemplate = mock(WhateverTheInterfaceIs.class);
// like inputXml you need to create testData for Uri etc.
// 'result' should be the needed result data to produce the
// real result of testClass.callWebService(...)
when(webServiceTemplate.sendSourceAndReceiveToResult(Uri, inputXml, new StreamResult(output))).thenReturn(result);
// or return other things, e.g.
// .thenThrow(new FoobarException());
// see mockito documentation for more possibilities
// Setup Testclass
TestClassImpl temp = new TestClassImpl();
temp.setWebServiceTemplate(generatedClient);
testClass = temp;
}
}