Mockk mocking Java "enum" singleton

Question

I'm working in a project which has some Java legacy code. One common pattern there is to create singletons using the "enum" approach:

enum MySingleton {
   INSTANCE;

   int answer;
   init {
     answer = 42;
   }

   int fun1() { return answer };

This INSTANCE object in reality has some complex dependencies which I cannot fulfill during unit tests. I thus would like to return a mocked MySingleton object whenever the caller uses MySingleton.INSTANCE. Is that possible?

Yes. https://mockk.io/#enumeration-mocks – k314159 Feb 13 '23 at 16:23 — k314159, Feb 13 '23 at 16:23

score 1 · Answer 1 · answered Feb 13 '23 at 16:13

As per the official Mockk documentation, It can be done like below.

enum class Enumeration(val goodInt: Int) {
    CONSTANT(35),
    OTHER_CONSTANT(45);
}

mockkObject(Enumeration.CONSTANT)
every { Enumeration.CONSTANT.goodInt } returns 42
assertEquals(42, Enumeration.CONSTANT.goodInt)

score 0 · Answer 2 · answered Aug 15 '22 at 10:14

0

you can mock enums using mockkObject(Enum)

answered Aug 15 '22 at 10:14

Max Makeichik

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Mockk mocking Java "enum" singleton

2 Answers2