isEmpty() returns false on empty list

[audunel]

Prerequisites

Please answer the following questions for yourself before submitting an issue.

• I am running the latest version (I am using springmockk 2.1.0, which in turn uses mockk 1.9.3)
• I checked the documentation and found no answer
• I checked to make sure that this issue has not already been filed

Expected Behavior

I am mocking a service which returns a list, and is supposed to return an empty list

val connector = mockk<Connector>()
val service = Service(connector)

@Test(expect = CustomException)
fun shouldThrowException() {
    every { connector.getList() } returns emptyList()
    service.foo()

Where foo() is defined as

foo() {
    val returnedList = connector.getList()
    if(returnedList.isEmpty()) {
        throw CustomException()
    }
    ...
}

Current Behavior

The test fails as returnedList.isEmpty() returns false

Failure Information (for bugs)

I have examined the returnedList val, and it has size = 0.

Steps to Reproduce

1. Set up a test where a mock service returns an empty list.
2. Run isEmpty() on the returned list.

Context

• MockK version: springmockk 2.0.1 (uses mockk 1.9.3)
• OS: macOS Mojave
• Kotlin version: 1.3.72
• JDK version: 1.8.0_172
• JUnit version: 4.13
• Type of test: unit test

14:35:44.849 [main] DEBUG io.mockk.impl.instantiation.AbstractMockFactory - Creating mockk for Service1 name=#1
14:35:45.482 [main] DEBUG io.mockk.impl.instantiation.AbstractMockFactory - Creating mockk for Service2 name=#2
14:35:45.588 [main] DEBUG io.mockk.impl.instantiation.AbstractMockFactory - Creating mockk for Service3 name=#3
14:35:45.643 [main] DEBUG io.mockk.impl.instantiation.AbstractMockFactory - Creating mockk for Service4 name=#4
14:35:47.051 [main] DEBUG io.mockk.impl.instantiation.AbstractMockFactory - Creating mockk for CustomClass name=child of #1#5
14:35:47.209 [main] DEBUG io.mockk.impl.instantiation.AbstractMockFactory - Creating mockk for List name=child of #2#6
14:35:47.213 [main] DEBUG io.mockk.impl.recording.states.AnsweringState - Answering ***@5754de72 on Service1(#1).***(***@5d625f21)
14:35:47.215 [main] DEBUG io.mockk.impl.instantiation.AbstractMockFactory - Creating mockk for List name=child of #2#7
14:35:47.216 [main] DEBUG io.mockk.impl.recording.states.AnsweringState - Answering List(child of #2#7) on Service2(#2).***-zKJe0gY(24000022, 123)
14:35:47.451 [main] DEBUG io.mockk.impl.recording.states.AnsweringState - Answering false on List(child of #2#7).isEmpty()
14:35:47.461 [main] DEBUG io.mockk.impl.instantiation.AbstractMockFactory - Creating mockk for List name=child of #3#8
14:35:47.462 [main] DEBUG io.mockk.impl.recording.states.AnsweringState - Answering List(child of #3#8) on Service3(#3).***(***)
14:35:47.467 [main] DEBUG io.mockk.impl.instantiation.AbstractMockFactory - Creating mockk for Iterator name=child^2 of #3#8#9
14:35:47.502 [main] DEBUG io.mockk.impl.recording.states.AnsweringState - Answering Iterator(child^2 of #3#8#9) on List(child of #3#8).iterator()
14:35:47.510 [main] DEBUG io.mockk.impl.recording.states.AnsweringState - Answering false on Iterator(child^2 of #3#8#9).hasNext()

java.lang.AssertionError: Expected exception: 
org.example.project.exceptions.CustomException

[fabiobauer]

Hey @audunel,

can you reproduce this issue while using MockK (1.9.3) only? I cannot see an error here, It looks like this issue belongs to springmockk.

class Connector {
    fun getList(): List<String> {
        return listOf("foo")
    }
}

class Service(private val connector: Connector) {
    fun foo() {
        val returnedList = connector.getList()
        if(returnedList.isEmpty()) {
            throw RuntimeException()
        }
    }
}

class Test1 {
    @Test(expected = RuntimeException::class)
    fun shouldThrowException() {
        val connector = mockk<Connector>()
        val service = Service(connector)

        every { connector.getList() } returns emptyList()
        service.foo()
    }
}

[audunel]

Hi @fabiobauer

When running your example code, I was not able to reproduce the issue. It seems like there's some other issue with our code. Thank you for your time.

[pikitgb]

For others looking for answer:

I was having similar issue using mockk_version = '1.10.3-jdk8'
in my case was that i was returning a mockk relaxed instead the empty list

Instead of using this:

every {
   connector.getList()
} returns mockk(relaxed = true) { // this caused the issue for me returning isEmpty() => false
   emptyList<MyItem>()
}

Use this:

every {
   connector.getList()
} returns emptyList<MyItem>()

[Raibaz]

This has also been fixed in more recent versions of mockk.