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Test fails on a null pointer exception when I use #InjectMocks

I am practising restful api endpoints using https://api.predic8.de/shop/docs
Here is my repo
I am getting a NPE failure when I try to use #InjectMocks during my TDD approach
However, I can make my test pass when I make a direct call in the setup()
vendorService = new VendorServiceImpl(VendorMapper.INSTANCE, vendorRepository);
I wanted to extend my learning by trying to create an endpoint for getting all vendors.
When I employ TDD along the way, but, my test getAllVendors() fails on a NPE when I try to use #InjectMocks but passes when I substitute it for a direct call in the setup() method.
The NPE is linked to the mapper class I think.
Here are the classes that I believe are useful. VendorServiceTest, VendorServiceImpl, VendorMapper.
I have commented out the direct call in the setup as I want to get the test passing using #InjectMocks
package guru.springfamework.services;
import guru.springfamework.api.v1.mapper.VendorMapper; import
guru.springfamework.api.v1.model.VendorDTO; import
guru.springfamework.domain.Vendor; import
guru.springfamework.repositories.VendorRepository; import
org.junit.Before; import org.junit.Test; import
org.mockito.InjectMocks; import org.mockito.Mock; import
org.mockito.MockitoAnnotations; import
org.springframework.test.web.servlet.MockMvc;
import java.util.Arrays; import java.util.List;
import static org.junit.Assert.*; import static
org.mockito.Mockito.when;
public class VendorServiceTest {
public static final String NAME = "Tasty";
public static final Long ID = 1L;
#Mock
VendorMapper vendorMapper;
#Mock
VendorRepository vendorRepository;
#InjectMocks
VendorServiceImpl vendorService;
//VendorService vendorService;
#Before
public void setUp() throws Exception {
MockitoAnnotations.initMocks(this);
//vendorService = new VendorServiceImpl(VendorMapper.INSTANCE, vendorRepository);
}
#Test
public void getAllVendors() {
//given
List<Vendor> vendors = Arrays.asList(new Vendor(), new Vendor(), new Vendor());
when(vendorRepository.findAll()).thenReturn(vendors);
//when
List<VendorDTO> vendorDTOList = vendorService.getAllVendors();
//then
assertEquals(3, vendorDTOList.size());
}
#Test
public void findByName() {
}
}
package guru.springfamework.services;
import guru.springfamework.api.v1.mapper.VendorMapper; import
guru.springfamework.api.v1.model.VendorDTO; import
guru.springfamework.repositories.VendorRepository; import
org.springframework.stereotype.Service;
import java.util.List; import java.util.stream.Collectors;
#Service public class VendorServiceImpl implements VendorService {
private final VendorMapper vendorMapper;
private final VendorRepository vendorRepository;
public VendorServiceImpl(VendorMapper vendorMapper, VendorRepository vendorRepository) {
this.vendorMapper = vendorMapper;
this.vendorRepository = vendorRepository;
}
#Override
public List<VendorDTO> getAllVendors() {
return vendorRepository
.findAll()
.stream()
.map(vendor -> {
VendorDTO vendorDTO = vendorMapper.vendorToVendorDTO(vendor);
vendorDTO.setVendorUrl("/api/v1/vendors/" + vendor.getId());
return vendorDTO;
})
.collect(Collectors.toList());
}
#Override
public VendorDTO findByName(String name) {
return vendorMapper.vendorToVendorDTO(vendorRepository.findByName(name));
}
#Override
public VendorDTO getVendorById(Long id) {
return vendorMapper.vendorToVendorDTO(vendorRepository.findById(id).orElseThrow(RuntimeException::new));
}
}
package guru.springfamework.api.v1.mapper;
import guru.springfamework.api.v1.model.VendorDTO; import
guru.springfamework.domain.Vendor; import org.mapstruct.Mapper; import
org.mapstruct.factory.Mappers;
#Mapper public interface VendorMapper {
VendorMapper INSTANCE = Mappers.getMapper(VendorMapper.class);
VendorDTO vendorToVendorDTO(Vendor vendor);
}
Does anyone know where and why I am going wrong?

The problem is that you created mock object for the mapper, but you didn't say what should happen when the method vendorToVendorDTO is called.
Therefore, when that method is called in the next line of code:
VendorDTO vendorDTO = vendorMapper.vendorToVendorDTO(vendor);
It will return null, and then in this line of code:
vendorDTO.setVendorUrl("/api/v1/vendors/" + vendor.getId());
You will get NullPointerException.
To make this work, change your getAllVendors() method as follows:
#Test
public void getAllVendors() {
//given
List<Vendor> vendors = Arrays.asList(new Vendor(), new Vendor(), new Vendor());
VendorDTO mockDto = mock(VendorDTO.class);
when(vendorRepository.findAll()).thenReturn(vendors);
when(vendorMapper.vendorToVendorDTO(any(Vendor.class))).thenReturn(mockDto);
//when
List<VendorDTO> vendorDTOList = vendorService.getAllVendors();
//then
assertEquals(3, vendorDTOList.size());
}
And the test should pass.

Have you tried to put #RunWith(MockitoJUnitRunner.class)/#ExtendsWith(MockitoExtension.class) over your test class?

Getting the value of parameters passed in #Factory annotated class using TestNG

Is it possible to get the value of parameters that are used to initialize a #Factory annotated test class from any of the ITestListener, ISuiteListener or any other listener methods?
Below is a sample test class. My intention is to get the value of the class init parameter 'value' using any of the listener methods, possibly.
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.testng.Assert;
import org.testng.annotations.DataProvider;
import org.testng.annotations.Factory;
import org.testng.annotations.Listeners;
import org.testng.annotations.Test;
import org.testng.reporters.EmailableReporter2;
#Listeners({ TestExecutionListener.class, EmailableReporter2.class })
public class TestClass {
private int value;
#Factory(dataProvider = "data", dataProviderClass = TestClass.class)
public TestClass(final int value) {
this.value = value;
}
#Test(alwaysRun = true)
public void testOdd() {
Assert.assertTrue(value % 2 != 0);
}
#Test(alwaysRun = true)
public void testEven() {
Assert.assertTrue(value % 2 == 0);
}
#DataProvider(name = "data")
public static Iterator<Object[]> data() {
List<Object[]> list = new ArrayList<>();
for (int i = 0; i < 2; i++) {
list.add(new Object[] { i });
}
return list.iterator();
}
}
Thanks in advance.

You can have access to your object from ITestResult#getInstance().
You'll just have to cast to object in the appropriate type (TestClass) and add a getter for value (or change its visibility).
ITestResult is available in many listeners.

Passing arrays to Parameterized JUnit

I am new to parameterized feature of JUnit 4.x and having a problem. My parameterized test consists of 3 integer arrays and I am having difficulty of how to declare them. What I have below generates run-time error:
testGeneral[0] caused an ERROR: argument type mismatch
argument type mismatch
java.lang.IllegalArgumentException
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
testGeneral[1] caused an ERROR: argument type mismatch
argument type mismatch
java.lang.IllegalArgumentException
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
Here is my code:
#RunWith(Parameterized.class)
public class MyArrayTest {
private Integer[] inputList1;
private Integer[] inputList2;
private Integer[] expectedList;
public MyArrayTest(Integer[] li1, Integer[] li2, Integer[] expected) {
// ========> Runtime error happens here. <=========
this.inputList1 = li1;
this.inputList2 = li2;
this.expectedList = expected;
}
#Parameterized.Parameters
public static Collection testCases() {
return Arrays.asList(new Object[][][] {
{{1,1,1}, {2,2,2}, {3,3,3}},
{{2,2,2}, {3,3,3}, {4,4,4}}
});
}
#Test
public void testGeneral() {
// Do some test with this.inputList1, this.inputList2,
// and verify with this.expectedList
// I am not even getting here yet.
}
}
I appreciate your help to correctly passing the three arrays to my tests.

The reason why it is failing is because your test expects Integer arrays whereas you are passing Object type. So you are expanding the type. Try this:
#Parameterized.Parameters
public static Collection testCases() {
return Arrays.asList(new Integer[][][] {
{{1,1,1}, {2,2,2}, {3,3,3}},
{{2,2,2}, {3,3,3}, {4,4,4}}
});
}

This solution uses junitparams, implements junitparams.converters.Converter and parses list of long values as parameters.
package example;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.util.Arrays;
import java.util.stream.Collectors;
import org.junit.Test;
import org.junit.runner.RunWith;
import junitparams.JUnitParamsRunner;
import junitparams.Parameters;
import junitparams.converters.ConversionFailedException;
import junitparams.converters.Converter;
import junitparams.converters.Param;
#RunWith(JUnitParamsRunner.class)
public class LongArrayParameterTest {
#Parameters({ "0|10", "1|10;20;30" })
#Test
public void test(final long otherParameter, #LongArrayParam final long[] expected) {
System.out.println(Arrays.stream(expected).boxed().map(l -> Long.toString(l)).collect(Collectors.toList()));
}
#Retention(RetentionPolicy.RUNTIME)
#Target(ElementType.PARAMETER)
#Param(converter = LongArrayConverter.class)
public #interface LongArrayParam {
}
public static class LongArrayConverter implements Converter<LongArrayParam, long[]> {
#Override
public void initialize(final LongArrayParam annotation) {
}
#Override
public long[] convert(final Object param) throws ConversionFailedException {
final String str = (String) param;
final String[] longStrings = str.split(";");
return Arrays.stream(longStrings).mapToLong(s -> Long.parseLong(s)).toArray();
}
}
}
This parser does not support empty list.

Loops to populate JUnit Parameters?

I am trying to extract individual URLs from an array list and have them act as the arguments for a series of JUnit tests. However, thus far I have been unable to do so.
This project focuses on web testing, and the method I am using retrieves the HTTP status code for a given URL.
The code below is the parameters section from the JUnit Test. It accepts the URL and Expected value as inputs, and compares them to the actual vale to determine whether or not each passes.
#Parameters
public static Collection<Object[]> testData(){
Object[][] data = new Object[][]{{"http://google.com",200}, {"http://yahoo.com", 404}};
return Arrays.asList(data);
}
Does anybody have any experience on looping through list arrays with parametrized JUnit testing? Ex)
Object [][] data = new Object [][]{{urlArray.get(0), statusArray.get(0},....{urlArray.get(i), statusArray.get(i)}}
Thank you for any help you can provide!
Full code below:
import java.io.IOException;
import java.util.Arrays;
import java.util.Collection;
import org.junit.Test;
import org.junit.Before;
import org.junit.Assert;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;
#RunWith(Parameterized.class)
public class CodeFinderTest extends CodeFinder {
private String url;
private int expected;
public CodeFinderTest(String url, int expected){
this.url = url;
this.expected = expected;
}
CodeFinder instance;
#Before
public void setup(){
instance = new CodeFinder();
}
#Parameters
public static Collection<Object[]> testData(){
Object[][] data = new Object[][]{{"http://google.com",200}, {"http://yahoo.com", 404}};
return Arrays.asList(data);
}
#Test
public void testFinder() throws IOException{
Assert.assertEquals(expected, instance.status(url));
}
}

The method that provides test data is a real method. Hence you can do this:
#Parameters
public static Collection<Object[]> testData(){
List<Object[]> data = new ArrayList<>();
Iterator<String> itUrl = urlArray.iterator();
Iterator<Integer> itStatus = statusArray.iterator();
while (itUrl.hasNext())
data.add(new Object [] {itUrl.next(), itStatus.next()});
return data;
}

Is it possible to use partial mocking for private static methods in PowerMock?

From the examples on the PowerMock homepage, I see the following example for partially mocking a private method with Mockito:
#RunWith(PowerMockRunner.class)
// We prepare PartialMockClass for test because it's final or we need to mock private or static methods
#PrepareForTest(PartialMockClass.class)
public class YourTestCase {
#Test
public void privatePartialMockingWithPowerMock() {
PartialMockClass classUnderTest = PowerMockito.spy(new PartialMockClass());
// use PowerMockito to set up your expectation
PowerMockito.doReturn(value).when(classUnderTest, "methodToMock", "parameter1");
// execute your test
classUnderTest.execute();
// Use PowerMockito.verify() to verify result
PowerMockito.verifyPrivate(classUnderTest, times(2)).invoke("methodToMock", "parameter1");
}
However, this approach does not seem to work when the private method we wish to mock is static. I wish to create a partial mock of the below class, with the readFile method mocked:
package org.rich.powermockexample;
import java.io.File;
import java.io.IOException;
import java.nio.charset.Charset;
import java.util.List;
import static com.google.common.io.Files.readLines;
public class DataProvider {
public static List<String> getData() {
List<String> data = null;
try {
data = readFile();
} catch (IOException e) {
e.printStackTrace();
}
return data;
}
private static List<String> readFile() throws IOException {
File file = new File("/some/path/to/file");
List<String> lines = readLines(file, Charset.forName("utf-8"));
return lines;
}
}
Please could someone let me know how this can be achieved?

After doing a bit more research, it seems that PowerMockito.spy() and PowerMockito.doReturn() are what is required here:
package com.richashworth.powermockexample;
import org.junit.Before;
import org.junit.BeforeClass;
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.util.ArrayList;
import java.util.List;
import static org.junit.Assert.assertEquals;
#RunWith(PowerMockRunner.class)
#PrepareForTest({DataProvider.class})
public class ResultsWriterTest {
private static List<String> mockData = new ArrayList<String>();
private ResultsWriter resultsWriter;
#BeforeClass
public static void setUpOnce() {
final String firstLine = "Line 1";
final String secondLine = "Line 2";
mockData.add(firstLine);
mockData.add(secondLine);
}
#Before
public void setUp() {
resultsWriter = new ResultsWriter();
}
#Test
public void testGetDataAsString() throws Exception {
PowerMockito.spy(DataProvider.class);
PowerMockito.doReturn(mockData).when(DataProvider.class, "readFile");
final String expectedData = "Line 1\nLine 2\n";
final String returnedString = resultsWriter.getDataAsString();
assertEquals(expectedData, returnedString);
}
}
For further details and the complete code listing, check out my blog post here: https://richashworth.com/post/turbocharge-your-mocking-framework-with-powermock/

Test class:
#RunWith(PowerMockRunner.class)
#PrepareForTest(DataProvider.class)
public class DataProviderTest {
#Test
public void testGetDataWithMockedRead() throws Exception {
mockStaticPartial(DataProvider.class, "readFile");
Method[] methods = MemberMatcher.methods(DataProvider.class, "readFile");
expectPrivate(DataProvider.class, methods[0]).andReturn(Arrays.asList("ohai", "kthxbye"));
replay(DataProvider.class);
List<String> theData = DataProvider.getData();
assertEquals("ohai", theData.get(0));
assertEquals("kthxbye", theData.get(1));
}
}
Class being tested (basically yours):
public class DataProvider {
public static List<String> getData() {
try {
return readFile();
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
private static List<String> readFile() throws IOException {
File file = new File("/some/path/to/file");
return readLines(file, Charset.forName("utf-8"));
}
}

In general, only use static mocking for classes that are beyond your control (e.g. java.io.File). Since DataProvider and readFile are your own, refactor DataProvider into a proper class (i.e. make its methods non-static), pull out readFile into a helper object and then mock that. See this answer https://stackoverflow.com/a/8819339/116509.