TDDing http4k Part 3: Adding another endpoint

Requirements:

  • Implement a "multiply" service, which will find the product of a number of integer values.

Tests:

package guide.tutorials.tdding_http4k._3

import com.natpryce.hamkrest.and
import com.natpryce.hamkrest.assertion.assertThat
import org.http4k.client.OkHttp
import org.http4k.core.Method.GET
import org.http4k.core.Request
import org.http4k.core.Response
import org.http4k.core.Status.Companion.BAD_REQUEST
import org.http4k.core.Status.Companion.OK
import org.http4k.hamkrest.hasBody
import org.http4k.hamkrest.hasStatus
import org.junit.jupiter.api.AfterEach
import org.junit.jupiter.api.BeforeEach
import org.junit.jupiter.api.Test
import guide.tutorials.tdding_http4k._3.Matchers.answerShouldBe

object Matchers {
    fun Response.answerShouldBe(expected: Int) {
        assertThat(this, hasStatus(OK).and(hasBody(expected.toString())))
    }
}

class EndToEndTest {
    private val client = OkHttp()
    private val server = MyMathServer(0)

    @BeforeEach
    fun setup() {
        server.start()
    }

    @AfterEach
    fun teardown() {
        server.stop()
    }

    @Test
    fun `all endpoints are mounted correctly`() {
        assertThat(client(Request(GET, "http://localhost:${server.port()}/ping")), hasStatus(OK))
        client(Request(GET, "http://localhost:${server.port()}/add?value=1&value=2")).answerShouldBe(3)
        client(Request(GET, "http://localhost:${server.port()}/multiply?value=2&value=4")).answerShouldBe(8)
    }
}

class AddFunctionalTest {
    private val client = MyMathsApp()

    @Test
    fun `adds values together`() {
        client(Request(GET, "/add?value=1&value=2")).answerShouldBe(3)
    }

    @Test
    fun `answer is zero when no values`() {
        client(Request(GET, "/add")).answerShouldBe(0)
    }

    @Test
    fun `bad request when some values are not numbers`() {
        assertThat(client(Request(GET, "/add?value=1&value=notANumber")), hasStatus(BAD_REQUEST))
    }
}

class MultiplyFunctionalTest {
    private val client = MyMathsApp()

    @Test
    fun `products values together`() {
        client(Request(GET, "/multiply?value=2&value=4")).answerShouldBe(8)
    }

    @Test
    fun `answer is zero when no values`() {
        client(Request(GET, "/multiply")).answerShouldBe(0)
    }

    @Test
    fun `bad request when some values are not numbers`() {
        assertThat(client(Request(GET, "/multiply?value=1&value=notANumber")), hasStatus(BAD_REQUEST))
    }
}

Production:

package guide.tutorials.tdding_http4k._3

import org.http4k.core.HttpHandler
import org.http4k.core.Method.GET
import org.http4k.core.Request
import org.http4k.core.Response
import org.http4k.core.Status.Companion.OK
import org.http4k.core.then
import org.http4k.filter.ServerFilters.CatchLensFailure
import org.http4k.lens.Query
import org.http4k.lens.int
import org.http4k.routing.bind
import org.http4k.routing.routes
import org.http4k.server.Http4kServer
import org.http4k.server.Jetty
import org.http4k.server.asServer

fun MyMathServer(port: Int): Http4kServer = MyMathsApp().asServer(Jetty(port))

fun MyMathsApp(): HttpHandler = CatchLensFailure.then(
    routes(
        "/ping" bind GET to { _: Request -> Response(OK) },
        "/add" bind GET to calculate { it.sum() },
        "/multiply" bind GET to calculate { it.fold(1) { memo, next -> memo * next } }
    )
)

private fun calculate(fn: (List<Int>) -> Int): (Request) -> Response {
    val values = Query.int().multi.defaulted("value", listOf())

    return { request: Request ->
        val valuesToCalc = values(request)
        val answer = if (valuesToCalc.isEmpty()) 0 else fn(valuesToCalc)
        Response(OK).body(answer.toString())
    }
}