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Apollo Mock

Apollo Kotlin integration

The apollo-network-transport module implements Apollo Kotlin’s NetworkTransport so an ApolloClient can talk to the mock data directly, in-process, instead of going through the server’s HTTP endpoint. It builds on executable-schema and handles queries, mutations and subscriptions uniformly.

This is a good fit for instrumented/unit tests: an ApolloClient can run against realistic fake data without starting a server or hitting the network.

Adding the dependency

build.gradle.kts
dependencies {
  implementation("com.apollographql.mock:apollo-network-transport:<version>")
}

MockNetworkTransport

import apollo.mock.networktransport.MockNetworkTransport
import com.apollographql.apollo.ApolloClient


val apolloClient = ApolloClient.Builder()
    .networkTransport(MockNetworkTransport(schemaText.toGQLDocument(), Path("data")))
    .build()
fun MockNetworkTransport(schema: GQLDocument, dataPath: Path): NetworkTransport

dataPath points at the directory of JSON files written by the generator, same as mockExecutableSchemaBuilder which it’s built on.

Queries and mutations execute once against the schema; subscriptions are forwarded to the schema’s subscribe() and stream one response per emitted event. Any exception thrown while resolving an operation is reported as an ApolloResponse with exception set, matching how other NetworkTransport implementations behave, rather than crashing the client.

Subscriptions

For a subscription field to resolve, its resolver must return a Flow<> of values instead of a plain value. The executable-schema module’s default resolver does this automatically: a Subscription root field pushes the same static fake value a Query field of the same shape would, once, and then completes — since the generator only produces static data, not a live event stream. Bring your own resolver instead if you need a subscription that pushes multiple events over time.