WireMock Dev Forum Talk

What is WireMock?

http://wiremock.org/

• A simulator for HTTP-based APIs
• A mock HTTP server
• A web server that serves canned responses
• An HTTP interaction recorder

Use Cases

• In-process unit testing
• Standalone integration testing
• Recording and playback of HTTP interactions
• Simulation of faults
  • Delays
  • Chunked responses
  • Bad responses

Setup

• Choice of two JARs
• Standard
• Standalone
  • Includes all dependencies
  • Used in example project

libraryDependencies += "com.github.tomakehurst" % "wiremock" % "2.19.0"
libraryDependencies += "com.github.tomakehurst" % "wiremock-standalone" % "2.19.0"

Configuration

• WireMockServer
• WireMockConfiguration.wireMockConfig
• Ports
  • port(8000)
  • dynamicPort()
  • httpsPort(8443)
  • dynamicHttpsPort()
• Proxy settings
• File locations

import com.github.tomakehurst.wiremock.WireMockServer
import com.github.tomakehurst.wiremock.core.WireMockConfiguration.wireMockConfig
import org.scalatest.{AsyncFlatSpec, BeforeAndAfterAll, BeforeAndAfterEach}

class SkeletonWireMockSpec extends AsyncFlatSpec with BeforeAndAfterAll with BeforeAndAfterEach {

  private val server: WireMockServer = new WireMockServer(wireMockConfig.dynamicPort())

  override def beforeAll(): Unit = {
    server.start()
  }

  override def beforeEach(): Unit = {
    server.resetAll()
  }

  override def afterAll(): Unit = {
    server.stop()
  }

}

Stubbing

• Matches request to response
• Pretty much like Mockito
• Matchers exist or URsL, headers, and body
  • Be very strict for a happy path GET
  • Be lax for an exceptional response
• DSL
• JSON mapping files
• No match results in 404 Not Found

server
  .stubFor(
    get("/hello")
      .willReturn(
        aResponse()
          .withStatus(200)
          .withBody("Hello, world!")
      )
  )

Verifying

• Verrify that a request was received
• Again similar to Mockito
• Again uses pattern matching
• Failures throw VerificationException

verify(getRequestedFor(urlEqualTo("/hello")))

Example REST API

This is the REST interface for the example connector

GET /person/:id

Request

• Headers: Accept = application/json

Responses

• 200 OK
  • Header: Content-Type = application/json
  • Body: JSON representation of a person
• 404 Not Found

POST /person

Request

• Header: Content-Type = application/json

Responses

• 201 Created
  • Header: Location = /person/:id

HttpClient

• Mockito or WireMock?
• Don't mock what you don't own
  • https://github.com/mockito/mockito/wiki/How-to-write-good-tests#dont-mock-type-you-dont-own
• HttpClient has complex behaviours
  • Adds headers
  • Converts to/from JSON
  • But doesn't (easily) let you handle an invalid response
  • Throws HttpException
• WireMock
  • Tests the behaviour of the whole connector stack
  • Does add some overhead