Java – mock nested method calls using mockito

javajunitmethodsmockingmockito

I have got 4 classes lets says A, B, C, D each calling on methods from another one.

now I have mocked class A, and want to mock a method using mockito

A a = Mockito.mock(A.class);

and want to get "foo" on recursive method calls like

a.getB().getC().getD() should return "foo"

I tried

when(a.getB().getC().getD()).thenReturn("foo");

but got nullPointerException

then I tried

doReturn("foo").when(a.getB().getC().getD());

then I got org.mockito.exceptions.misusing.UnfinishedStubbingException:

I know I can create objects of B, C and D, or can even write something like

B b = mock(B.class) or A.setB(new B())

and so on.

But can't I do that in a single shot?
Any help would be appreciated.

Best Answer

Adding RETURNS_DEEP_STUBS did the trick:

A a = Mockito.mock(A.class, Mockito.RETURNS_DEEP_STUBS);

Related Solutions

Java inner class and static nested class

From the Java Tutorial:

Nested classes are divided into two categories: static and non-static. Nested classes that are declared static are simply called static nested classes. Non-static nested classes are called inner classes.

Static nested classes are accessed using the enclosing class name:

OuterClass.StaticNestedClass

For example, to create an object for the static nested class, use this syntax:

OuterClass.StaticNestedClass nestedObject = new OuterClass.StaticNestedClass();

Objects that are instances of an inner class exist within an instance of the outer class. Consider the following classes:

class OuterClass {
    ...
    class InnerClass {
        ...
    }
}

An instance of InnerClass can exist only within an instance of OuterClass and has direct access to the methods and fields of its enclosing instance.

To instantiate an inner class, you must first instantiate the outer class. Then, create the inner object within the outer object with this syntax:

OuterClass outerObject = new OuterClass()
OuterClass.InnerClass innerObject = outerObject.new InnerClass();

see: Java Tutorial - Nested Classes

For completeness note that there is also such a thing as an inner class without an enclosing instance:

class A {
  int t() { return 1; }
  static A a =  new A() { int t() { return 2; } };
}

Here, new A() { ... } is an inner class defined in a static context and does not have an enclosing instance.

What’s the difference between a method and a function

A function is a piece of code that is called by name. It can be passed data to operate on (i.e. the parameters) and can optionally return data (the return value). All data that is passed to a function is explicitly passed.

A method is a piece of code that is called by a name that is associated with an object. In most respects it is identical to a function except for two key differences:

A method is implicitly passed the object on which it was called.
A method is able to operate on data that is contained within the class (remembering that an object is an instance of a class - the class is the definition, the object is an instance of that data).

(this is a simplified explanation, ignoring issues of scope etc.)

Best Answer

Related Solutions

Java inner class and static nested class

What’s the difference between a method and a function

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