Is there any way, using Mockito or PowerMockito, to intercept calls to non-static methods of an object, or at least of a singleton object?
An example is provided by the following classes:
public class Singleton {
private static Singleton INSTANCE = null;
private Singleton(Object parameter) {}
public static Singleton getInstance(Object parameter) {
if (INSTANCE == null) {
INSTANCE = new Singleton(parameter);
}
return INSTANCE;
}
public String process(String a, String b) {
return (a + b);
}
// Other methods
}
public class Foreign {
private Foreign() {}
public static void main(String[] args) {
System.out.println(Singleton.getInstance(new Object()).process("alpha", "beta"));
}
}
The Singleton object is created in a Foreign class, outside the control of some test code (not shown above). Neither of these two classes can be modified. The objective is to intercept calls to the non-static process() method in the test code so that, for certain values, a different result is returned, e.g. the call
Singleton.getInstance(new Object()).process("alpha", "beta");
mocked to return "alpha-beta" instead of the expected "alphabeta".
One solution could be intercepting the Singleton.getInstance() method to instantiate a custom subclass of the Singleton, e.g. using
public class SubSingleton extends Singleton {
public SubSingleton(Object parameter) {
super(parameter);
}
public String process(String a, String b) {
if ("alpha".equals(a) && "beta".equals(b)) {
return a + "-" + b;
}
return super.process(a + b);
}
}
Then, calls to the Singleton.process() method would be intercepted as in:
Object parameter = new Object();
PowerMockito.doReturn(new SubSingleton(parameter)).when(Singleton.class, "getInstance", parameter);
However, the Singleton class above only provides a private constructor, so it cannot be extended. Using PowerMockito.whenNew() to return a partial mock (spy) will also not work, since the Singleton class does not provide a no-args constructor.
Can the desired mocking be implemented in any other way? Can it be done for non-singleton classes?
Firstly, you can use whenNew for objects with constructor with some params:
#RunWith(PowerMockRunner.class)
#PrepareForTest(Singleton.class)
public class SingletonPrivateNewTest {
#Mock
Singleton singletonMock;
#Before
public void setUp() throws Exception {
PowerMockito.whenNew(Singleton.class)
.withAnyArguments()
.thenReturn(singletonMock);
}
#Test
public void testMockNew() throws Exception {
Mockito.when(singletonMock.process(anyString(), anyString())).thenReturn("sasa");
Foreign.main(new String[0]);
}
}
Secondly, why not stub getInstance instead of new:
#RunWith(PowerMockRunner.class)
#PrepareForTest(Singleton.class)
public class SingletonPrivateNewTest {
#Test
public void testMockNew() {
PowerMockito.mockStatic(Singleton.class);
Singleton singletonMock = Mockito.mock(Singleton.class);
PowerMockito.when(Singleton.getInstance(any())).thenReturn(singletonMock);
Mockito.when(singletonMock.process(anyString(), anyString())).thenReturn("sasa");
Foreign.main(new String[0]);
}
}
Thirdly, to intercept the process method:
create real singleton
create a mock singleton
mock static getInstance to return the mock. NOTE: you must call mockStatic after getting real instance.
use thenAnswer to check the arguments on process call
return desired answer if they match desired pattern
else call real method on real singleton
#RunWith(PowerMockRunner.class)
#PrepareForTest(Singleton.class)
public class SingletonPrivateNewTest {
#Test
public void testMockNew() {
var singletonReal = Singleton.getInstance(new Object());
var singletonMock = Mockito.mock(Singleton.class);
PowerMockito.mockStatic(Singleton.class);
PowerMockito.when(Singleton.getInstance(any())).thenReturn(singletonMock);
Mockito.when(singletonMock.process(anyString(), anyString())).thenAnswer((args) -> {
String a = args.getArgument(0);
String b = args.getArgument(1);
if ("alpha".equals(a) && "beta".equals(b)) {
return "sasa";
} else {
return singletonReal.process(a, b);
}
});
Foreign.main(new String[0]);
}
}
And finally, use a spy instead of a mock
#RunWith(PowerMockRunner.class)
#PrepareForTest(Singleton.class)
public class SingletonPrivateNewTest {
#Test
public void testMockNew() {
var singletonReal = Singleton.getInstance(new Object());
var singletonMock = Mockito.spy(singletonReal);
PowerMockito.mockStatic(Singleton.class);
PowerMockito.when(Singleton.getInstance(any())).thenReturn(singletonMock);
Mockito.when(singletonMock.process("alpha", "beta")).thenReturn("sasa");
// NOTE: real method is called for other args
Foreign.main(new String[0]);
}
}
Related
I am trying to write unit test cases for one of the methods in code.Below is the method
public boolean isValid() {
if(object == null)
return false
//do something here and return value.
}
The object is created by this method which is done before without getter setter method.
private Object returnObject() {
object = Axis2ConfigurationContextFactory.getConfigurationContext();
return object;
}
When I try to test isValid(), the object is always null, so it never goes in the code to do something.
I was checking if there is any way to skip that line or make the object not null. I also tried creating an object using returnObject method. But it uses Axis library classes which throws error if it does not find certain data. What can be done in this case? I am dealing with legacy code so any pointers would be helpful.
Edit : Adding test implementation.
#PowerMockIgnore({ "javax.xml.*", "org.w3c.dom.*", "javax.management.*" })
public class ClassTest {
private ClassTest classTestObj;
#BeforeMethod
public void callClassConstructor() {
classTestObj = //call class constructor
}
#BeforeClass
public void setUpClass() throws Exception {
MockitoAnnotations.initMocks(this);
}
#Test
public boolean isValidTest() {
Boolean result = classTestObj.isValid();
Assert.assertEquals(result);
}
}
As I mentioned in the before comment, you can make use of MockedStatic to mock the static method - https://javadoc.io/static/org.mockito/mockito-core/4.4.0/org/mockito/Mockito.html#static_mocks
So your code will somewhat look like the below one if you are making use of Mockito instead of PowerMockito.
#RunWith(MockitoJUnitRunner.class)
public class ClassTest
{
#Mock
private Object mockAxis2ConfigurationContextFactoryObject;
#Test
public boolean isValidTest() {
try (MockedStatic<Axis2ConfigurationContextFactory> mockedStatic = mockStatic(Axis2ConfigurationContextFactory.class)) {
mockedStatic.when(()->Axis2ConfigurationContextFactory.getConfigurationContext()).thenReturn(mockAxis2ConfigurationContextFactoryObject);
Boolean result = classTestObj.isValid();
Assert.assertEquals(result);
}
}
public Data extraMethod(Data data) // interface Data
{
Data d = Singleton.getInstance().sort(data.get() , "desc");
//do something, logical
return d;
}
How can I mock the object Data(the singleton extra return result), class Singleton has a static method getInstance and no public constructor. I want to test the logical part, test extraMethod without Data sort operation.
You could get away without PowerMock if you would spy your class under test and create a package level method that would be return the Singleton.
You still need to set-up what should happen when the sort method is invoked:
1) Class under test
public Data extraMethod(Data data) // interface Data
{
Data d = getSingleton().sort(data.get() , "desc");
//do something, logical
return d;
}
Singleton getSingleton(){
return Singleton.getInstance();
}
2) Test
#Spy
private MyClass myClassSpy = new MyClass();
#Mock
Singleton singletonStub;
#Mock
Data dataStub;
#Before
public void init(){
MockitoAnnotations.initMocks(this);
}
#Test
public void test() throws Exception{
// Arrange
doReturn(singletonStub).when(myClassSpy).getSingleton();
when(dataStub.get()).thenReturn(...);
when(singletonStub.sort(any(Data.class), "desc")).thenReturn(/* some data*/);
// Act and Assert
}
I have below piece of code in method.
AdminServiceProxy proxy=new AdminServiceProxy();
boolean flag=proxy.isAdminFree();
How to mock "AdminServiceProxy " using Jmock. Since object is getting created using new operator.
You can't.
One possible solution is to create an AdminServiceProxyFactory interface and implementation:
public interface AdminServiceProxyFactory {
public AdminServiceProxy createAdminServiceProxy();
}
public class AdminServiceProxyFactoryImpl {
public AdminServiceProxy createAdminServiceProxy() {
return new AdminServiceProxy();
}
}
Then in your class add a setter and private attribute:
public class Foo {
private AdminServiceProxyFactory adminServiceProxyFactory;
...
public void setAdminServiceProxyFactory(AdminServiceProxyFactory factory) {
adminServiceProxyFactory = factory;
}
public myMethod() {
...
AdminServiceProxy proxy=adminServiceProxyFactory.createAdminServiceProxy();
boolean flag=proxy.isAdminFree();
...
}
}
Now you can create a mock AdminServiceProxyFactory and inject it into your class. You then tell your mock factory to return a mock AdminServiceProxy when it is called.
jMock does not support the mocking of "future objects" or the mocking of constructors.
Other mocking libraries provide such support. One of them (which I developed) is JMockit, whose syntax was originally inspired by jMock's "Expectations". In this case, we could have:
#Test
public void exampleTestThatMocksAFutureObject(#Mocked AdminServiceProxy proxy) {
new Expectations() {{ proxy.isAdminFree(); result = true; }};
// Call code under test which instantiates an AdminServiceProxy...
boolean adminFree = new AdminServiceProxy().isAdminFree();
assertTrue(adminFree);
}
My class structure is as follows:
public class MyParentClass {
void doSomethingParent() {
System.out.println("something in parent");
}
}
public class MyClass extends MyParentClass {
protected String createDummyRequest(Holder myHolder) {
//...
super.doSomethingParent();//I want to avoid this
//...
callingDB();
return "processedOutput";
}
private void callingDB() {
System.out.println("Calling to DB");
}
}
Then my unit test:
public class UnitTest {
public void testCreateDummyRequest() {
//create my mock holder
Holder mockHolder = new Holder();
MyClass mockObj = Mockito.mock(MyClass.class);
//mock doSomethingParent()
//mock callingDB()
//as mockObj is a fully mock, but I need to run my real method
//Mockito.when(mockObj.createDummyRequest(mockHolder)).thenCallRealMethod();
mockObj.createDummyRequest(mockHolder);
//Problem: doSomethingParent() is getting called though I have mocked it
}
}
How do I prevent the calling of the super.doSomethingParent() in my method? (method which I am writing my test)
With this class structure mocking and testing is real hard. If possible, I'd advice to change the structure as in mist cases a class structure that's hard to mock and test is equally hard to extend and maintain.
So if you could change your class structure to something similar to:
public class MyClass {
private DoSomethingProvider doSomethingProvider;
private DbConnector dbConnector;
public MyClass (DoSomethingProvider p, DbConnector c) {
doSomethingProvicer = p;
dbConnector = c;
}
protected String createDummyRequest(Holder myHolder){
//...
doSomethingProvider.doSomethingParent();
//...
dbConnector.callingDB();
return "processedOutput";
}
}
Then you could easily create your instance with mocks of DoSomethingProvider and DbConnector and voila....
If you can't change your class structure you need to use Mockito.spy instead of Mockito.mock to stub specific method calls but use the real object.
public void testCreateDummyRequest(){
//create my mock holder
Holder mockHolder = new Holder();
MyClass mockObj = Mockito.spy(new MyClass());
Mockito.doNothing().when(mockObj).doSomething();
mockObj.createDummyRequest(mockHolder);
}
Note: Using the super keyword prevents Mockito from stubbing that method call. I don't know if there is a way to stub calls to super. If possible (as in you didn't override the parent method in your class), just ommit the keyword.
I faced similar issue, so I find out that using spy() can hepld.
public class UnitTest {
private MyClass myObj;
#Before
public void setUp() throws Exception {
MockitoAnnotations.initMocks(this);
myObj= spy(new MyClass());
}
#Test
public void mockedSuperClassMethod(){
doNothing().when((MyParentClass )myObj).doSomethingParent();
//...
}
}
This approach works for me.
I found another approach, which turned out to be very useful in my case.
In the case I had, I needed to create a new class extending another, which included a very complex (legacy code) protected final method. Due to the complexity, it wasn't really possible to refactor to use composition, so here's what I came up with.
Let's say I have the following:
abstract class Parent {
public abstract void implementMe();
protected final void doComplexStuff( /* a long parameter list */) {
// very complex legacy logic
}
}
class MyNewClass extends Parent {
#Override
public void implementMe() {
// custom stuff
doComplexStuff(/* a long parameter list */); // calling the parent
// some more custom stuff
}
}
Here's how I rearranged this code:
abstract class Parent {
public abstract void implementMe();
protected final void doComplexStuff( /* a long parameter list */) {
// very complex legacy logic
}
}
interface ComplexStuffExecutor {
void executeComplexStuff(/* a long parameter list, matching the one from doComplexStuff */);
}
class MyNewClass extends Parent {
private final ComplexStuffExecutor complexStuffExecutor;
MyNewClass() {
this.complexStuffExecutor = this::doComplexStuff;
}
MyNewClass(ComplexStuffExecutor complexStuffExecutor) {
this.complexStuffExecutor = complexStuffExecutor;
}
#Override
public void implementMe() {
// custom stuff
complexStuffExecutor.doComplexStuff(/* a long parameter list */); // either calling the parent or the injected ComplexStuffExecutor
// some more custom stuff
}
}
When creating instance of MyNewClass for "production" purposes, I can use the default constructor.
When writing unit tests, however, I'd use the constructor, where I can inject ComplexStuffExecutor, provide a mock there and only test my custom logic from MyNewClass, i.e.:
class MyNewClassTest {
#Test
void testImplementMe() {
ComplexStuffExecutor complexStuffExecutor = Mockito.mock(ComplexStuffExecutor.class);
doNothing().when(complexStuffExecutor).executeComplexStuff(/* expected parameters */);
MyNewClass systemUnderTest = new MyNewClass(complexStuffExecutor);
// perform tests
}
}
At first glance, it seems like adding some boilerplate code just to make the code testable. However, I can also see it as an indicator of how the code should actually look like. Perhaps one day someone (who would find courage and budget ;) ) could refactor the code e.g. to implement the ComplexStuffExecutor with the logic from doComplexStuff from Parent, inject it into MyNewClass and get rid of inheritance.
Here is how it can be done
public class BaseController {
public void method() {
validate(); // I don't want to run this!
}
}
public class JDrivenController extends BaseController {
public void method(){
super.method()
load(); // I only want to test this!
}
}
#Test
public void testSave() {
JDrivenController spy = Mockito.spy(new JDrivenController());
// Prevent/stub logic in super.method()
Mockito.doNothing().when((BaseController)spy).validate();
// When
spy.method();
// Then
verify(spy).load();
}
Source: https://blog.jdriven.com/2013/05/mock-superclass-method-with-mockito/
I need to test handleIn() method using Mockito.
However the code need to call this legacy code Util.getContextPDO which is a static method.
Note that in testing environment this Util.getContextPDO is always returns Exception, and I intend to bypass this Util.getContextPDO() by always return a dummy IPDO.
public class MyClass {
public IPDO getIPDO()
{
return Util.getContextPDO(); // note that Util.getContextPDO() is a static, not mockable.
}
public String handleIn(Object input) throws Throwable
{
String result = "";
IPDO pdo = getIPDO();
// some important business logic.
return result;
}
}
Initially I thought this achieveable by using spy() of the class "MyClass", so I can mock the return value of getIPDO(). Below is my initial effort using spy ()
#Test
public void testHandleIn() throws Exception
{
IPDO pdo = new PDODummy();
MyClass handler = new MyClass ();
MyClass handler2 = spy(handler);
when(handler2.getIPDO()).thenReturn(pdo);
PDOUtil.setPDO(pdo, LogicalFieldEnum.P_TX_CTGY, "test123");
IPDO pdoNew = handler2.getIPDO();
Assert.assertEquals("test123,(PDOUtil.getValueAsString(pdoNew, LogicalFieldEnum.P_TX_CTGY)));
}
However the when(handler2.getIPDO()).thenReturn(pdo); is throwing the Exception that I want to avoid ( because handler2.getIPDO() ) seems to call the real method.
Any idea on how to test this part of code?
A good technique for getting rid of static calls on 3rd party API is hiding the static call behind an interface.
Let's say you make this interface :
interface IPDOFacade {
IPDO getContextPDO();
}
and have a default implementation that simply calls the static method on the 3rd party API :
class IPDOFacadeImpl implements IPDOFacade {
#Override
public IPDO getContextPDO() {
return Util.getContextPDO();
}
}
Then it is simply a matter of injecting a dependency on the interface into MyClass and using the interface, rather than the 3rd party API directly :
public class MyClass {
private final IPDOFacade ipdoFacade;
public MyClass(IPDOFacade ipdoFacade) {
this.ipdoFacade = ipdoFacade;
}
private IPDO getIPDO() {
return ipdoFacade.getContextPDO();
}
public String handleIn(Object input) throws Throwable
{
String result = "";
IPDO pdo = getIPDO();
someImportantBusinessLogic(pdo);
return result;
}
...
}
In your unit test, you can then easily mock your own interface, stub it any way you like and inject it into the unit under test.
This
avoids the need to make private methods package private.
makes your tests more readable by avoiding partial mocking.
applies inversion of control.
decouples your application from a specific 3rd party library.
Changed my testing to :
#Test
public void testHandleIn() throws Exception
{
IPDO pdo = new PDODummy();
MyClass handler = new MyClass ();
MyClass handler2 = spy(handler);
doReturn(pdo ).when( handler2 ).getIPDO();
PDOUtil.setPDO(pdo, LogicalFieldEnum.P_TX_CTGY, "test123");
IPDO pdoNew = handler2.getIPDO();
Assert.assertEquals("test123,(PDOUtil.getValueAsString(pdoNew, LogicalFieldEnum.P_TX_CTGY)));
}
Solved after reading Effective Mockito.
when(handler2.getIPDO()).thenReturn(pdo);
Will actually call the method and then return pdo regardless.
Whereas:
doReturn(pdo).when(handler2).getIPDO();
Will return pdo without calling the getIPDO() method.