how to isolate cases in KoinTest - koin

Question

I need to inject different instances of classes in my various JUnit tests that use Koin. When run one at a time, the tests pass, but when run all together, they fail. Test foo is producing values that could only come from the objected injected in test bar, so I must not be properly isolating Koin. The actual tests are more complicated integration tests, and the sample below was my attempt to make something self-contained that reproduces the issue, but unfortunately these tests pass when run together. The structure is the same, though.
import com.google.common.truth.Truth.assertThat
import kotlinx.coroutines.delay
import kotlinx.coroutines.runBlocking
import org.junit.After
import org.junit.Before
import org.junit.Test
import org.koin.core.component.KoinComponent
import org.koin.core.component.inject
import org.koin.core.context.GlobalContext.startKoin
import org.koin.core.context.GlobalContext.stopKoin
import org.koin.test.KoinTest
import org.koin.test.mock.declare
import kotlin.time.Duration.Companion.seconds
class KoinSampleTest : KoinTest {
#Before
fun setup() {
startKoin { }
}
#After
fun teardown() = stopKoin()
#Test
fun foo() = runBlocking<Unit> {
val namedUser = Foo()
declare<Named> { namedUser }
val user = NamedUser()
assertThat(user.sayName()).isEqualTo("foo")
}
#Test
fun bar() = runBlocking<Unit> {
val namedUser = Bar()
declare<Named> { namedUser }
val user = NamedUser()
assertThat(user.sayName()).isEqualTo("bar")
}
}
interface Named {
val name: String
}
class Foo(override val name: String = "foo") : Named
class Bar(override val name: String = "bar") : Named
class NamedUser : KoinComponent {
val nameContainer by inject<Named>()
suspend fun sayName(): String {
delay(2.seconds) // simulate some latency of in-process RPC
return nameContainer.name
}
}
Are there some best practices for KoinTest that I'm missing here?

Answer 1

The answer: The class with the injected field can't be a singleton, or Kotlin will do what you asked it to and only ever instantiate the field once.
package com.laptopera.control
import com.google.common.truth.Truth.assertThat
import kotlinx.coroutines.delay
import kotlinx.coroutines.runBlocking
import org.junit.After
import org.junit.Ignore
import org.junit.Before
import org.junit.Test
import org.koin.core.component.KoinComponent
import org.koin.core.component.inject
import org.koin.core.context.GlobalContext.startKoin
import org.koin.core.context.GlobalContext.stopKoin
import org.koin.test.KoinTest
import org.koin.test.mock.declare
import kotlin.time.Duration.Companion.seconds
class KoinSampleTest : KoinTest {
#Before fun setup() { startKoin { } }
#After fun teardown() = stopKoin()
#Test
fun foo() = runBlocking<Unit> {
val namedUser = Foo()
declare<Named> { namedUser }
val user = NamedUser
assertThat(user.sayName()).isEqualTo("foo")
}
#Test
fun bar() = runBlocking<Unit> {
val namedUser = Bar()
declare<Named> { namedUser }
val user = NamedUser
assertThat(user.sayName()).isEqualTo("bar")
}
}
interface Named { val name: String }
class Foo(override val name: String = "foo") : Named
class Bar(override val name: String = "bar") : Named
// The test fails if this is an object, and passes if it is a class, because nameContainer is only ever instantiated
// once per runtime in a singleton/object.
object NamedUser : KoinComponent {
val nameContainer by inject<Named>()
suspend fun sayName(): String {
delay(2.seconds)
return nameContainer.name
}
}