I have a class in Scala that looks like this:
class A {
private val b = new B()
def doSomething() {
b.someMethod();
}
}
How can I unit test doSomething()? How can I mock b here?
I tried something like this:
val b = mock[B]
when(b.someMethod()).thenReturn(xx)
val class_to_test = new A()
class_to_test.doSomething()
I am using Mockito and MockitoSugar.
The problem with your last code snippet is that val b = mock[B] is a different variable from the b field of your class. You can fix this by modifying the class to take b as an optional argument:
class A(b: B = new B) {
def doSomething(): Unit = {
b.someMethod()
}
}
Now your test becomes:
val b = mock[B]
when(b.someMethod()).thenReturn(xx)
val classToTest = new A(b)
classToTest.doSomething()
This technique is called Dependency Injection. You can read more about it here: What is dependency injection?
If you don't want to expose b as a public constructor parameter, you can use a package-private constructor coupled with a public constructor or factory method that provides the default value of b:
class A private[myPackage](b: B) {
def this() = this(new B) // The public constructor doesn't expose b.
def doSomething(): Unit = {
b.someMethod()
}
}
Then just make sure your tests are in the same package so they can still call the constructor that takes b.