MockServerRule Test using Ktor

MockServerRule.kt

class MockServerRule(
    private val appStartUpOverrideMockRequests: List<MockRequest> = emptyList<MockRequest>()
) : TestRule {

    private var overrideRequests = mutableMapOf<String, MockRequest>()

    override fun apply(
        base: Statement,
        description: Description
    ): Statement {
        return object : Statement() {
            override fun evaluate() {
                appStartUpOverrideMockRequests.forEach {
                    overrideRequests[it.path] = it
                }
                val server = embeddedServer(CIO, port = 8080) {
                    intercept(ApplicationCallPipeline.Call) {
                        overrideRequests[call.request.path()]?.let {
                            call.respondText(
                                text = it.response,
                                status = it.httpStatusCode,
                                contentType = ContentType.Application.Json
                            )
                            finish()
                        }
                    }
                }.apply {
                    application.defaultRoutes()
                    start(wait = false)
                }
                try {
                    server.application.monitor.subscribe(ApplicationStarted) {
                        base.evaluate()
                    }
                } finally {
                    server.stop(0, 0) // Initiate shutdown
                    overrideRequests.clear()
                }
            }
        }
    }

    // mid test override 
    fun overrideRequest(vararg mockRequests: MockRequest) {
        mockRequests.forEach { request ->
            overrideRequests[request.path] = request
        }
    }

    fun removeOverrides() {
        overrideRequests.clear()
    }
}

data class MockRequest(
    val path: String,
    val response: String,
    val httpStatusCode: HttpStatusCode
)


/// usage

    @get:Rule(order = 1)
    var hiltRule = HiltAndroidRule(this)
    
    @get:Rule(order = 2)
    val mockServerRule = MockServerRule()
    /**
     or pre app start up MockServerRule(listOf(MockRequest(blah blah))
    */

    @get:Rule(order = 3)
    val composeTestRule = createAndroidComposeRule<MainActivity>()

    @Before
    fun setUp() {
        hiltRule.inject()
    }

    
    @Test
    fun testSomething() {
        // test steps...
        // mid test override
        mockServerRule.overrideRequest(
            MockRequest("/api/error", "{}", HttpStatusCode.BadRequest),
        )
      // rest of the test
    }