# Mock Apollo Client on the Kotlin Multiplatform
**URL:** https://community.apollographql.com/t/mock-apollo-client-on-the-kotlin-multiplatform/221
**Category:** Client SDKs
**Tags:** kotlin, client, mobile
**Created:** [May 26, 2021, 4:30pm UTC](https://community.apollographql.com/t/mock-apollo-client-on-the-kotlin-multiplatform/221 "2021-05-26T16:30:51Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@rb090](https://community.apollographql.com/u/rb090)
#### Post date: [May 26, 2021, 4:30pm UTC](https://community.apollographql.com/t/mock-apollo-client-on-the-kotlin-multiplatform/221/1 "2021-05-26T16:30:51Z")
Hi apollo community 👋,
I am using the experimental apollo client dependency for the Kotlin Multiplatform:
```
com.apollographql.apollo:apollo-runtime-kotlin:2.5.7
```
I really love this library it works very good and provides the functionality desired.
I am trying to write unit tests for my request classes and I want to mock the ApolloClient dependency. I read that one [https://spectrum.chat/apollo/apollo-android/mocking-apollo-in-kotlin-multiplaform-mobile~935224f4-16db-41f5-92a4-6d9de4c14d54](https://spectrum.chat/apollo/apollo-android/mocking-apollo-in-kotlin-multiplaform-mobile~935224f4-16db-41f5-92a4-6d9de4c14d54) and it helps me to understand how to mock the ApolloClient, thanks Martin for the answer there 👍.
The only question left is, is there a possibility to mock some header into the apollo response? Can someone please help me here with an advice? I refer to this class here: [https://github.com/apollographql/apollo-android/blob/main/apollo-runtime-kotlin/src/commonTest/kotlin/com/apollographql/apollo/mock/MockNetworkTransport.kt](https://github.com/apollographql/apollo-android/blob/main/apollo-runtime-kotlin/src/commonTest/kotlin/com/apollographql/apollo/mock/MockNetworkTransport.kt)
@mbonnin maybe you have an idea here? Probably it is a small code change I need to do 😬.
---
### Author:  [@mbonnin](https://community.apollographql.com/u/mbonnin)
#### Post date: [May 27, 2021, 7:07am UTC](https://community.apollographql.com/t/mock-apollo-client-on-the-kotlin-multiplatform/221/2 "2021-05-27T07:07:05Z")
Hi! can you share a bit more about what header you want to mock?
`ApolloResponse` has a `executionContext` property that can contain a `HttpExecutionContext`: [https://github.com/apollographql/apollo-android/blob/49d4768dc381f51acc38256d28a9dd99afea9f1b/apollo-runtime-kotlin/src/jvmMain/kotlin/com/apollographql/apollo/network/http/ApolloHttpNetworkTransport.kt#L131](https://github.com/apollographql/apollo-android/blob/49d4768dc381f51acc38256d28a9dd99afea9f1b/apollo-runtime-kotlin/src/jvmMain/kotlin/com/apollographql/apollo/network/http/ApolloHttpNetworkTransport.kt#L131)
Would that work?
---
### Author:  [@rb090](https://community.apollographql.com/u/rb090)
#### Post date: [May 27, 2021, 10:42am UTC](https://community.apollographql.com/t/mock-apollo-client-on-the-kotlin-multiplatform/221/3 "2021-05-27T10:42:07Z")
Hi @mbonnin
thanks a lot for getting back to me regarding my question.
I am using exactly that `MockNetworkTransport` from GitHub from your sample. I need to mock the `ApolloResponse` for my unit tests. That “mocked behavior” I put to an `ApolloClient` for my tests. My class which mocks the apollo client looks like this atm:
```auto
class ApolloRequestClientMock {
private var networkTransport: MockNetworkTransport = MockNetworkTransport()
fun simpleApolloClient(headers: Map?): ApolloClient {
return ApolloClient(
networkTransport = networkTransport,
// The 'TestLoggerExecutor' is the one from GitHub
// https://github.com/apollographql/apollo-android/blob/main/apollo-runtime-kotlin/src/commonTest/kotlin/com/apollographql/apollo/mock/TestLoggerExecutor.kt
interceptors = listOf(TestLoggerExecutor)
)
}
fun setExpectedSuccessForNetworkTransportWith(responseJson: String) {
networkTransport.trySend(responseJson).isSuccess
}
fun setExpectedFailureForNetworkTransportBecauseDataEmpty() {
networkTransport.trySend("").isFailure
}
fun setExpectedFailureForNetworkTransportWith(failureResponse: String) {
networkTransport.trySend(failureResponse).isFailure
}
}
```
If the `ApolloResponse` does not contain a header named `__typename` I receive this error when executing my tests:
```auto
java.lang.NullPointerException: corrupted response reader, expected non null value for __typename
```
To have this `__typename` header I added a little bit of code to the `MockNetworkTransport`, regarding your answer and now the class is looking like this
```auto
@ApolloExperimental
@ExperimentalCoroutinesApi
internal class MockNetworkTransport(
private val mockResponseChannel: Channel = Channel(capacity = Channel.BUFFERED)
) : NetworkTransport, SendChannel by mockResponseChannel {
private var expectedStatusCode: Int = 200
private var expectedHeaders: Map = mapOf("__typename" to "some-typename")
override fun execute(
request: ApolloRequest,
executionContext: ExecutionContext
): Flow> {
return flow {
emit(
ApolloResponse(
requestUuid = request.requestUuid,
response = request.operation.parse(mockResponseChannel.receive().encodeUtf8()),
executionContext = request.executionContext + HttpExecutionContext.Response(
statusCode = expectedStatusCode,
headers = expectedHeaders
)
)
)
}
}
fun setExpected(statusCode: Int) {
expectedStatusCode = statusCode
}
}
```
But it still does not work, I receive the same error of missing `__typename`. Is there anything I can change in my code to make it work?
---
### Author:  [@rb090](https://community.apollographql.com/u/rb090)
#### Post date: [May 27, 2021, 3:59pm UTC](https://community.apollographql.com/t/mock-apollo-client-on-the-kotlin-multiplatform/221/4 "2021-05-27T15:59:32Z")
I fixed the issue. It wasn’t about the header 🤦♀️. This `__typename` should be in the response body and not in the header - for some reasons I thought that this field belongs in the header. Beginner issue.
So this one is solved. With the sample mock code from Martin writing unit tests for amp by mocking the `ApolloClient` works great 👍
---
### Author:  [@mbonnin](https://community.apollographql.com/u/mbonnin)
#### Post date: [May 27, 2021, 4:15pm UTC](https://community.apollographql.com/t/mock-apollo-client-on-the-kotlin-multiplatform/221/5 "2021-05-27T16:15:06Z")
@rb090 yep, exactly. `__typename` is a graphql field as you found out 👍.
Thanks for writing what I think is the first Android post on these forums 😃!