In kotlin, how do I mock a suspend function that wraps a callback?

I suggest using MockK for your tests, which is more coroutine-friendly.

To mock a coroutine, you can use coEvery and returns like below:

val interf = mockk<SomeInterface>()
coEvery { a.doSomething(any()) } returns Outcome.OK

When you need to

on .... do return ..

and method is suspended, with mockito you can use this:

use this lib mockito-kotlin
Mock your object, lets name it myObject (myObject has suspend method named isFoo)

then:

 myObject.stub {
    onBlocking { isFoo() }.doReturn(true)
}

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