Develop Reference

Mocking a separate class function from the class that is being tested

I have a function that is calling a method from another class. This class and method have been tested and are using live data which makes my test inconsistent with the expected values I hard coded.
public class MyClass{
public void functionToBeTested(String params){
//stuff to do
Caller call = new Caller();
callResult = call.post(someJSON);
//do stuff with callResult
}
}
Here is the junit:
public class TestMyClass{
MyClass testClass = new MyClass();
Caller mock;
#Before
public void setup(){
premadeAnswer = new String(file);
mock = Mockito.mock(Caller.class);
Mockito.when(mock.post(Mockito.any())).thenReturn(premadeAnswer);
}
#Test
public void studentFees_CorrectSSN(){
assertEquals(expected.getThing(), testClass.functionToBeTested("PARAMS").getThing());
}
}
I was pretty sure I did everything right but obviously its not mocking and instead calling the function ans behaving as expected if it wasn't a junit. If I had to make a guess as to whats happening it would be that even though I am creating a mocked object and using when/thenReturn it is not attached to MyClass testClass object.

That won't work because Caller is not injected into functionToBeTested function.
Mockito.when(mock.post(Mockito.any())).thenReturn(premadeAnswer);
this when statement is working only on your mocked instance, inside functionToBeTested you are creating a new instance of Caller.
Either change functionToBeTested(String params) to functionToBeTested(String params, Caller call) and then pass your mocked Caller instance or try mocking Caller constructor.
More info about second approach here

I noticed in your first block of code that you shared, that there is no return value specified. I added void in the code block below.
public class MyClass{
public void functionToBeTested(String params){
//stuff to do
Caller call = new Caller();
callResult = call.post(someJSON);
//do stuff with callResult
}
}

PowerMock: stub methods from parent class

I'm using PowerMock and I'd like to know how to keep all behavior of the child class, but stub super calls that may be overriden by the child.
Say I have this class:
public class A {
public String someMethod() {
return "I don't want to see this value";
}
}
and a sub class:
public class B extends A {
#Override
public String someMethod() {
return super.someMethod() + ", but I want to see this one";
}
}
How do I stub the call to super.someMethod()?
I've tried
#Test
public void test() {
B spy = PowerMockito.spy(new B());
PowerMockito.doReturn("value").when((A)spy).someMethod();
assertEquals("value, but I want to see this one", spi.someMethod());
}

You can try suppressing the methods from the Parent class,
PowerMockito.suppress(methodsDeclaredIn(A.class));
Here's an article on Stubbing, suppressing and replacing with PowerMock that might be of some use.
https://www.jayway.com/2013/03/05/beyond-mocking-with-powermock/

Don't forget to add #PrepareForTest({ParentClassToSupress.class}) on your test class. Then you can do as Steve suggests and suppress methods in the parent: PowerMockito.suppress(methodsDeclaredIn(ParentClassToSupress.class));

The cast you're attempting is not going to work as you are expecting. However, I think you have a couple of options to get around this, certainly with PowerMockito.
Take a look at this StackOverflow answer.

Design Approach and Using Reflection to run methods in Java

I have a question. I have multiple classes in a package: Let's say package is
com.myPackage.first
And this package has the following classes:
firstGood
secondGood
thirdBad
fourthGood
Each of these classes have a method with the same name but different implementation. So say each have a one particular function called:
public void runMe(){
}
For now I want to come up with a way to given a class name, it'll go inside the class and run that particular method.
So conceptually, my method will look like those:
ArrayList<Class> classList ; // where classList is a list of classes I want to run
public void execute(){
for(Class c : classList){
// Go inside that class, (maybe create an intance of that class) and run the method called run me
}
}
or
public void execute(Class c, String methodToRun){
for(Class c : classList){
// Go inside that class, (maybe create an intance of that class) and run the method called run me
}
}
For now. what I have been able to do is get the name of the classes I want to run the
runMe()
method. So I have been able to come with a way to get the arraylist of classes I want to run. So what I need help with is coming up with a method such that it takes a class name and run the method I want it to. Any help is appreciated. Thanks

I suggest having a look at Class.forName ( ... ) to get the class object, Class.newInstance(); if your classes have a default constructor (or Class.getDeclaredConstructor(...) otherwise) to create a new instance and then Class.getDeclaredMethod( ... ) to find the method and invoke it.
All of this without any regard if your idea is really a good one, since I really didn't quite understand WHY you want to do what you want to do...

interface Me {
void runMe();
}
Then let all classes implement Me.
And have a list of Mes
List<Class<Me>> ...
Then
void test(Class<Me> cl) {
Me me = cl.newInstance();
me.runMe();
}

My adage is always use reflection to solve a problem - now you have two problems. In view of that have you considered a simple pattern like this:
interface Runner {
public void runMe();
}
static abstract class BaseRunner implements Runner {
public BaseRunner() {
// Automagically register all runners in the RunThem class.
RunThem.runners.add(this);
}
}
class FirstGood extends BaseRunner implements Runner {
#Override
public void runMe() {
System.out.println(this.getClass().getSimpleName() + ":runMe");
}
}
class SecondGood extends BaseRunner implements Runner {
#Override
public void runMe() {
System.out.println(this.getClass().getSimpleName() + ":runMe");
}
}
static class RunThem {
static final Set<Runner> runners = new HashSet<>();
static void runThem() {
for (Runner r : runners) {
r.runMe();
}
}
}
public void test() {
Runner f = new FirstGood();
Runner s = new SecondGood();
RunThem.runThem();
}
Here all of your runMe objects extend a base class whose constructor installs the object in a Set held by the class that calls their runMe methods.

inline
void execute() throws Exception{
for (Class<?> c : classesList)
{
//If you don't already have an instance then you need one
//note if the method is static no need for any existing instance.
Object obj = Class.forName(c.getName());
// name of the method and list of arguments to pass
Method m = c.getDeclaredMethod(methodName,null);
//method accessibility check
if(!m.isAccessible())
m.setAccessible(true);
//invoke method if method with arguements then pass them as new Object[]{arg0...} instead of null
//if method is static then m.innvoke(null,null)
m.invoke(obj, null);
}
}

I would recommend using an Interface that defines the runMe() method and then have all your classes implement that interface. Then you would have a list of this Interface:
List<MyInterface> classes = new ArrayList<MyInterface>();
Then you could easily iterate over it and invoke "runMe()" on all of them or if you only want to invoke it for instances of a certain class you could do it like this:
public void execute(Class classForWhichToExecute) {
for (MyInterface myInterface : classes) {
if (classForWhichToExecute.isAssignableForm(myInterface)) {
myInterface.runMe();
}
}
}
Of course this wouldn't work if your method is a static method - so adding more information from your side would help.

I would suggest to use an interface with a common method to override in each class. So that any class can be casted to interface and use its method to execute the method.
interface GoodAndBad{
public void runMe();
}
Implemented class
class FirstGood implements GoodAndBad{
#override
public void runMe(){
// Code to be executed
}
}
You can use execute() method as follows
public void execute(List<GoodAndBad> classList){
for(GoodAndBad c : classList){
c.runMe();
// Go inside that class, (maybe create an intance of that class) and
// run the method called run me
}
}
Change the Class to GoodAndBad interface to change the other method too.
This is loosely coupling objects to support favor over composition in Java Object Oriented Design Patterns.
Never use Strings of method names to execute a method at anytime. There are plenty of other cool solutions for that using design patterns.

PowerMock throwing null pointer exception at queue.add method

I am using Powermock to unit test a class.
The Class has a queue of List of objects as private member.
I am using PowerMock createPartialMock to partially mock two of the methods (say A and B) and then explicitly calling method C and then verify.
Class Sample {
Queue<List> q;
public C() {
A();
B();
q.add(List);
}
private A() {}
private B() {}
}
Class Test {
void testSomeMethod() {
Sample mock = PowerMock.createPartialMock(Sample.class, "A", "B");
PowerMock.expectPrivate(Sample.class, A).thenReturn("true");
PowerMock.expectPrivate(Sample.class, B).thenReturn("true");
mock.C();
PowerMock.verify(mock);
}
}
Now when I run the tests, PowerMock throws exception at q.add(List); line.
Can anyone please point out what mistake am I making?
Do I have expect q.add() method call as well?

You should somehow assign a value to q attribute of Sample class.
This can be done on constructor, by a setter method or by reflection (Whitebox class or pure Java reflection code).
If you need to check whether a item is added to q, create a mock of Queue interface.

How should I mock out a single method inside an object I'm trying to test?

I have a problem with a class that I am testing where in almost every method I want to test, one of the first things each method does is call this one specific method. This method that is called once by all of these other methods takes a long time to execute. I don't want to have to wait for this every time I run my tests, it really is just a huge waste of time.
I attempted to #Spy the method using Mocktio, but I ran into problems because the really long method doesn't return anything. Can someone suggest a good way to mock out a single method inside a class I am trying to test?
Example:
public class myClass {
public void methodOne() {
reallyLongMethod();
// More code
}
public void methodTwo() {
reallyLongMethod();
// More code
}
.
.
.
public void methodN() {
reallyLongMethod();
// More code
}
public void reallyLongMethod() {
}
}
This is the class I am trying to test. I want to test all of the 'methodX()' methods. I don't want to run reallyLongMethod everysingle time however.
So, is there a way to use Mockito 'Spy' to stub out reallyLongMethod()? Even though it doesn'treturn anything?

You can use a Spy with doNothing(), but make sure you use the spy during the test. Mockito spies copy the original, instead of delegating to it.
#RunWith(MockitoJUnitRunner.class)
public class YourTest {
// Option 1:
// #Spy MyClass myClass = new MyClass();
// Option 2 (see #Before method)
MyClass myClass;
#Before public void ignoreReallyLongMethod() {
myClass = spy(new MyClass()); // discard original
doNothing().when(myClass).reallyLongMethod();
}
#Test public void methodOneWorks() {
myClass.methodOne(); // you're using the spy here
assertEquals(42, myClass.getFoo());
}
}
Though this does evoke a code smell, don't mock or stub the class under test, as long as you're careful to test the method behavior (methodOne) and not the stubbed behavior (reallyLongMethod) you'll be good to go. If you do want to test reallyLongMethod you'll want to use a different object instance or else you'll "test" the doNothing() call alone. Do bear in mind that if reallyLongMethod and your other methods have any negative interactions, these tests won't tell you about that.
By the way, you can also do the equivalent without using Mockito, which may make a little clearer what you are or aren't doing with your mocks:
#RunWith(JUnit4.class)
public class YourTest {
MyClass myClass;
#Before public void createMyClass() {
myClass = new MyClass() { // create an anonymous inner class
#Override public void reallyLongMethod() {} // that does nothing here
};
}
}