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Using PowerMockito to mock a class with #Inject variables and static methods

I am trying to use a power mock to mock a class with #Injects and static methods called in another class constructor. But for some reason it seems to be throwing MissingMethodInvocationException in PowerMockito.when.
#Named
public class InstanceLocationWrapperFactory {
#Inject
private InstanceLocation instanceLocation;
private static InstanceLocation internalInstanceLocation;
#PostConstruct
private void load(){
internalInstanceLocation = instanceLocation;
}
public static InstanceLocation getInstance(){
return internalInstanceLocation;
}
}
I am trying to use it to instantiate a value inside the constructor of another class like as follows. (InstanceLocation is a interface which is implemented by DefaultInstanceLocationImpl class.)
class A{
InstanceLocation instance;
A(){
instance = InstanceLocationWrapperFactory.getInstance();
}
public String myMethod(){
/* using instance here to do some logic*/
}
}
I am trying to write a test like this
#RunWith(PowerMockRunner.class)
#PrepareForTest({A.class, InstanceLocationWrapperFactory.class})
public class ATest {
#Test
public void myTestCase1{
InstanceLocation instanceLocation = mock(DefaultInstanceLocationImpl.class);
PowerMockito.mockStatic(InstanceLocationWrapperFactory.class);
PowerMockito.when(InstanceLocationWrapperFactory.getInstance()).thenReturn(instanceLocation);
when(instance.getMethod()).thenReturn("something");
}
But when i run the above code for some reason i keep getting the below error for the line PowerMockito.when(InstanceLocationWrapperFactory.getInstance()).thenReturn(instanceLocation);.
org.mockito.exceptions.misusing.MissingMethodInvocationException:
when() requires an argument which has to be 'a method call on a mock'.
For example:
when(mock.getArticles()).thenReturn(articles);
Also, this error might show up because:
1. you stub either of: final/private/equals()/hashCode() methods.
Those methods *cannot* be stubbed/verified.
Mocking methods declared on non-public parent classes is not supported.
2. inside when() you don't call method on mock but on some other object.
Can someone please help me understand if I am doing something wrong or missing something here.

Powermock verifyPrivate does not work with any()

I have a private method whose invocation I want to test without caring about the arguments. I want to test if it was called at all or not.
MyClass.java
public void doStuff(){
unload(args);
}
private void unload(List<String> args) {
//
}
So I used following:
MyClasstest.java
MyClass myClass = PowerMockito.spy(new MyClass());
myClass.doStuff();
verifyPrivate(myClass, times(1)).invoke("unload",any(List.class));
// verifyPrivate(myClass, times(1)).invoke("unload",any()); //same result with this
This test fails with following exception:
Wanted but not invoked com.MyClass.unload(
null );
However, there were other interactions with this mock .......
(actual values with which it was called)
Can verifyPrivate be called with only actual arguments & not with any()?

Here is a working example of what you are trying to do:
You might just missing the #PrepareForTest annotation, which has to point to the correct class. If your class is an external one use #PrepareForTest(MyClass.class), the example below shows it with an internal class.
#RunWith(PowerMockRunner.class)
#PrepareForTest(MyClassTest.class)
public class MyClassTest {
static class MyClass {
public void doStuff(){
unload(null);
}
private void unload(List<String> args) {
}
}
#Test
public void test() throws Exception {
MyClass myClass = PowerMockito.spy(new MyClass());
myClass.doStuff();
PowerMockito.verifyPrivate(myClass, Mockito.times(1)).invoke("unload", Mockito.any());
}
}
Note that you should consider whether you really want to do this in a UnitTest. Normally your UnitTest should not be concerned about whether a private method is used or not, it should be focused on verifying that the correct result is returned or the correct object state is reached.
By adding knowledge about the internal behaviour of the class into it, you test is tightly coupled to the implementation which might not be a good thing.

Static method invocation

Can we call a static method without mentioning the class name in Java?

Yes you can. Check out static imports. You have to mention the class name in the import statement, but after that you don't have to.e.g. from the linked article:
import static java.lang.Math.abs;
import static java.lang.Math.max;
int xDist = abs(destination.getX() - x);
int yDist = abs(destination.getY() - y);
return max(xDist, yDist);
Introduced in Java 5.

Yes, you can call a static method without mentioning the class name. There's the import static (see JLS 7.5.4 for exact mechanism), but even without it, if the name can be resolved (see JLS 15.12.1 for exact mechanism) without fully qualifying the class, it will work.
The following code compiles and prints "Hello world!" as expected.
import static java.lang.System.out;
public class Test {
static String greeting() {
return "Hello world!";
}
public static void main(String[] args) {
out.println(greeting());
}
}
out in the println statement is actually a static field access of the class java.lang.System, not a static method, but it's a static member access nonetheless. greeting() is a static method invocation, and the class name can be omitted since its reference can be resolved without fully qualifying the name.
Now let's ask if this is a good idea. Unless you're calling a static method from within its class, IT'S NOT a good idea generally to omit the class name!!!
Let's focus on static import first. A quote from the guide:
So when should you use static import? Very sparingly! Only use it when you'd otherwise be tempted to declare local copies of constants, or to abuse inheritance (the Constant Interface Antipattern). In other words, use it when you require frequent access to static members from one or two classes. If you overuse the static import feature, it can make your program unreadable and unmaintainable, polluting its namespace with all the static members you import. Readers of your code (including you, a few months after you wrote it) will not know which class a static member comes from. Importing all of the static members from a class can be particularly harmful to readability; if you need only one or two members, import them individually. Used appropriately, static import can make your program more readable, by removing the boilerplate of repetition of class names.
The case is made stronger by the following example:
class Base {
void task1() {
System.out.println("Base.task1");
}
static void task2() {
System.out.println("Base.task2");
}
}
class Child extends Base {
void task1() {
System.out.println("Child.task1");
}
static void task2() {
System.out.println("Child.task2");
}
}
//....
Base sweetChildOMine = new Child();
sweetChildOMine.task1(); // prints "Child.task1"
sweetChildOMine.task2(); // prints "Base.task2"
What a surprise! You'd think that since sweetChildOMine has a reference to an instance of Child, sweetChildOMine.task2() should print "Child.task2" because it's overridden by Child class, right?
WRONG! A static method can not be overridden! It can only be hidden by a subclass! In fact, if you tried to do the right thing and add the #Override annotation to task2, it would not compile!
From JLS 15.12.4.4 Locate method to invoke:
If the invocation mode is static, no target reference is needed and overriding is not allowed. Method m of class T is the one to be invoked.
In fact, this problem is covered in Java Puzzlers Puzzle 48: All I Get Is Static. The conclusion given at the end of the puzzle is this:
In summary, qualify static methods invocations with a class name, or don't qualify them at all if you're invoking them from within their own class, but never qualify them with an expression. Also, avoid hiding static methods. Together, these guidelines help eliminate the misleading appearance of overriding with dynamic dispatch for static methods.
It is best to follow all these recommendations together, so:
If you're calling a static method within its own class, don't qualify
Otherwise, qualify with the class name
If you're doing this a lot within one class, consider static import of that specific method
Try not to static import all members with *
Never qualify with an expression
Don't hide a static method; you can't #Override it, it'll only cause confusion
See also:
Why doesn’t Java allow overriding of static methods ?
When do you use Java’s #Override annotation and why?

Yes, adding to Brian Agnew you can call static methods through an instance of that class type as well.

Yes you can call a static method without the class name. For example, if you are calling it within another static method of the same class.
public class TestStatic{
static void hello()
{
System.out.println("Hello World");
}
static void hello2()
{
hello();
System.out.println("Welcome to java");
}
public static void main(String[] args)
{
hello2();
}
}

Yes.
class CallStaticMethodTest {
public static void staticMethodOne() {
System.out.println("Static method one");
}
// Invoke from a non-static method
public void instanceMethodOne() {
staticMethodOne();// Calling static method without mentioning the class name
}
// Invoke from another static method:
public static void staticMethodTwo() {
staticMethodOne();
}
}

java basics static method

can a static method be invoked before even a single instances of the class is constructed?

absolutely, this is the purpose of static methods:
class ClassName {
public static void staticMethod() {
}
}
In order to invoke a static method you must import the class:
import ClassName;
// ...
ClassName.staticMethod();
or using static imports (Java 5 or above):
import static ClassName.staticMethod;
// ...
staticMethod();

As others have already suggested, it is definitely possible to call a static method on a class without (previously) creating an instance--this is how Singletons work. For example:
import java.util.Calendar;
public class MyClass
{
// the static method Calendar.getInstance() is used to create
// [Calendar]s--note that [Calendar]'s constructor is private
private Calendar now = Calendar.getInstance();
}
If you mean, "is it possible to automatically call a specific static method before the first object is initialized?", see below:
public class MyClass
{
// the static block is garanteed to be executed before the
// first [MyClass] object is created.
static {
MyClass.init();
}
private static void init() {
// do something ...
}
}

Yes, that is exactly what static methods are for.
ClassName.staticMethodName();

Yes, because static methods cannot access instance variables, so all the JVM has to do is run the code.

Static methods are meant to be called without instantiating the class.

Yes, you can access it by writing ClassName.methodName before creating any instance.

Not only can you do that, but you should do it.

In fact, there are a lot of "utility classes", like Math, Collections, Arrays, and System, which are classes that cannot be instantiated, but whose whole purpose is to provide static methods for people to use.

Yes, that's definitely possible. For example, consider the following example...
class test {
public static void main(String arg[]) {
System.out.println("hello");
}
}
...if then we run it, it does execute, we never created a instance of the class test. In short, the statement public static void main(String arg[]) means execute the main method without instantiating the class test.

Invoke static initializer again

Once a class is loaded is there a way to invoke static initializers again?
public class Foo {
static {
System.out.println("bar");
}
}
Edit:
I need to invoke the static initializer because I didn't write the original class and the logic I need to invoke is implemented in the static initializer.

Put the initalisation code in a separate public static method, so you can call it from the static initializer and from elsewhere?

One circumstance in which the logic would be run more than once is if the class is loaded multiple times by different ClassLoaders. Note that in this instance, they are essentially different classes.
Generally, though, these are one-shot deals. If you want to be able to invoke the logic multiple times, do as others have suggested and put it in a static method.

I agree with Earwicker's answer. Just extract the static initialization to a separate static method.
public class Foo {
static {
Foo.initialize();
}
public static void initialize() {
System.out.println("bar");
}
}

In case you really want the exact answer to your exact question, the answer is no. It's not possible to invoke a static initializer or an instanceInitializer via reflection.
The docs clearly says :
for getDeclaredMethod(String name) :
If the name is "<init>" or "<clinit>" a NoSuchMethodException is raised.
for getDeclaredMethods() :
The class initialization method is not included in the returned array.
So no, it's not possible to invoke it, even via reflection.

you could try extending the class which contains the static code, and then put in your own static initializer. Not quite sure if it works, but :
public class OldBadLibraryClass {
static {
System.out.println("oldBadLibrary static init");
}
}
//next file
public class MyBetterClass extends OldBadLibraryClass {
static {
System.out.println("MyBetterClass init");
}
}
public class Test {
public static void main(String[] args) {
new MyBetterClass();
}
}
see if the above prints in the order you expect. On my machine, it worked.
Though this is totally a hack, and is quite brittle. It would really be much better to modify the old class to have an init() method that can be overridden.

Here https://stackoverflow.com/a/19302726/2300018 is a post from me, where I re-load a utility class to re-run the static initializer for unit testing.