Mocking the Kotlin SupabaseClient for unit testing

Question

TLDR : Here is a minimally reproduceable example. You do not need a Supabase account / database to get the error.

I have some code like this, which performs some simple transformation of data before saving it in Supabase

    suspend fun saveClones(owner: String, repository: String, clones: GitHubClones): List<ResultClone> {
        val zeClones = clones.clones.map {
            Clone(
                owner = owner,
                repository = repository,
                count = it.count,
                uniques = it.uniques,
                timestamp = it.timestamp
            )
        }

        return client.postgrest["clone"].insert(zeClones, upsert = true, onConflict = "owner, repository, timestamp").decodeList<ResultClone>()
    }

I'd like to check that the data going in the insert call is what I expect it to be. I've tried to mock the client using mockk as such

val supabaseClient = mockk<SupabaseClient>()
val postgrest = mockk<Postgrest>()
val postgrestBuilder = mockk<PostgrestBuilder>()
val postgrestResult = PostgrestResult(body = null, headers = Headers.Empty)

every { supabaseClient.postgrest } returns postgrest
every { postgrest["path"] } returns postgrestBuilder
coEvery { postgrestBuilder.insert(values = any<List<Path>>()) } returns postgrestResult

but when running my test, I am facing the following error :

java.lang.IllegalStateException: Plugin rest not installed or not of type Postgrest. Consider installing Postgrest within your supabase client builder
    at io.github.jan.supabase.postgrest.PostgrestKt.getPostgrest(Postgrest.kt:172)
    at nl.lengrand.GitHubTrafficStoreTest$setUp$1.invoke(GitHubTrafficStoreTest.kt:53)
    at nl.lengrand.GitHubTrafficStoreTest$setUp$1.invoke(GitHubTrafficStoreTest.kt:53)

What would be the correct way to unit test that function? It looks like I also cannot really use test containers with Supabase, making integration tests equally as difficult.

Answer 1

Coming back here just to mentioned that I decided to go another direction, which I'm pretty satisfied with actually. I created a simple Docker Compose setup that I run with test containers and which simulate a simple Supabase instance. No need for mocking any more. It's more "integration tests" than "unit tests" at that point though.

The full blog about it, but in short :

version: '3'

# Thanks https://github.com/mattddowney/compose-postgrest/blob/master/README.md
services:

  ################
  # postgrest-db #
  ################
  postgrest-db:
    image: postgres:16-alpine
    ports:
      - "5432:5432"
    environment:
      - POSTGRES_USER=${POSTGRES_USER}
      - POSTGRES_PASSWORD=${POSTGRES_PASSWORD}
      - POSTGRES_DB=${POSTGRES_DB}
      - DB_SCHEMA=${DB_SCHEMA}
    volumes:
      - "./initdb:/docker-entrypoint-initdb.d"
    networks:
      - postgrest-backend
    restart: always

  #############
  # postgrest #
  #############
  postgrest:
    image: postgrest/postgrest:latest
    ports:
      - "3000:3000"
    environment:
      - PGRST_DB_URI=postgres://${POSTGRES_USER}:${POSTGRES_PASSWORD}@postgrest-db:5432/${POSTGRES_DB}
      - PGRST_DB_SCHEMA=${DB_SCHEMA}
      - PGRST_DB_ANON_ROLE=${DB_ANON_ROLE}
      - PGRST_JWT_SECRET=${PGRST_JWT_SECRET}
    networks:
      - postgrest-backend
    restart: always

  #############
  # Nginx     #
  #############
  nginx:
    image: nginx:alpine
    restart: always
    tty: true
    volumes:
      - ./nginx.conf:/etc/nginx/conf.d/default.conf
    ports:
      - "80:80"
      - "443:443"
    networks:
      - postgrest-backend

networks:
  postgrest-backend:
    driver: bridge

and the test file :

import io.github.jan.supabase.SupabaseClient
import io.github.jan.supabase.createSupabaseClient
import io.github.jan.supabase.postgrest.Postgrest
import kotlinx.coroutines.runBlocking
import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.BeforeEach
import org.junit.jupiter.api.Test
import org.testcontainers.containers.ComposeContainer
import org.testcontainers.junit.jupiter.Container
import org.testcontainers.junit.jupiter.Testcontainers
import java.io.File

@Testcontainers
class MainKtTestTestContainers {

    // The jwt token is calculated manually (https://jwt.io/) based on the private key in the docker-compose.yml file, and a payload of {"role":"postgres"} to match the user in the database
    private val jwtToken = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJyb2xlIjoicG9zdGdyZXMifQ.88jCdmcEuy2McbdwKPmuazNRD-dyD65WYeKIONDXlxg"

    private lateinit var supabaseClient: SupabaseClient

    @Container
    var environment: ComposeContainer =
        ComposeContainer(File("src/test/resources/docker-compose.yml"))
            .withExposedService("postgrest-db", 5432)
            .withExposedService("postgrest", 3000)
            .withExposedService("nginx", 80)

    @BeforeEach
    fun setUp() {
        val fakeSupabaseUrl = environment.getServiceHost("nginx", 80) +
                ":" + environment.getServicePort("nginx", 80)

        supabaseClient = createSupabaseClient(
            supabaseUrl = "http://$fakeSupabaseUrl",
            supabaseKey = jwtToken
        ) {
            install(Postgrest)
        }
    }

    @Test
    fun testEmptyPersonTable(){
        runBlocking {
            val result = getPerson(supabaseClient)
            assertEquals(0, result.size)
        }
    }

    @Test
    fun testSavePersonAndRetrieve(){
        val randomPersons = listOf(Person("Jan", 30), Person("Jane", 42))

        runBlocking {
            val result = savePerson(randomPersons, supabaseClient)
            assertEquals(2, result.size)
            assertEquals(randomPersons, result.map { it.toPerson() })

            val fetchResult = getPerson(supabaseClient)
            assertEquals(2, fetchResult.size)
            assertEquals(randomPersons, fetchResult.map { it.toPerson() })
        }
    }
}