Example of capturing logging output in Play Framework

gistfile1.txt

/*
 * Copyright (C) 2009-2017 Lightbend Inc. <https://www.lightbend.com>
 */
package play.it.http

import ch.qos.logback.classic.Logger
import ch.qos.logback.classic.spi.ILoggingEvent
import ch.qos.logback.core.AppenderBase
import org.slf4j.LoggerFactory
import org.specs2.execute.AsResult
import play.api.inject.guice.GuiceApplicationBuilder
import play.api.mvc._
import play.api.test._
import play.api.{ Configuration, Mode }
import play.core.server.ServerConfig
import play.it._

import scala.collection.mutable.ArrayBuffer

class NettyRequestHeadersSpec extends RequestHeadersSpec with NettyIntegrationSpecification

class AkkaHttpRequestHeadersSpec extends RequestHeadersSpec with AkkaHttpIntegrationSpecification

trait RequestHeadersSpec extends PlaySpecification with ServerIntegrationSpecification with HttpHeadersCommonSpec {

  sequential

  def withServerAndConfig[T](configuration: (String, Any)*)(action: (DefaultActionBuilder, PlayBodyParsers) => EssentialAction)(block: Port => T) = {
    val port = testServerPort

    val serverConfig: ServerConfig = {
      val c = ServerConfig(port = Some(testServerPort), mode = Mode.Test)
      c.copy(configuration = c.configuration ++ Configuration(configuration: _*))
    }
    running(play.api.test.TestServer(serverConfig, GuiceApplicationBuilder().appRoutes { app =>
      val Action = app.injector.instanceOf[DefaultActionBuilder]
      val parse = app.injector.instanceOf[PlayBodyParsers]
      ({
        case _ => action(Action, parse)
      })
    }.build(), Some(integrationServerProvider))) {
      block(port)
    }
  }

  def withServer[T](action: (DefaultActionBuilder, PlayBodyParsers) => EssentialAction)(block: Port => T) = {
    withServerAndConfig()(action)(block)
  }

  "Play request header handling" should {

    "not complain about invalid User-Agent headers" in {

      // This test modifies the global (!) logger to capture log messages.
      // The test will not be reliable when run concurrently. However, since
      // we're checking for the *absence* of log messages the worst thing
      // that will happen is that the test will pass when it should fail. We
      // should not get spurious failures which would cause our CI testing
      // to fail. I think it's still worth including this test because it
      // will still often report correct failures, even if it's not perfect.

      import scala.collection.immutable

      def recordLogEvents[T](block: => T): immutable.Seq[ILoggingEvent] = {

        /** Collects all log events that occur */
        class RecordingAppender extends AppenderBase[ILoggingEvent] {
          private val eventBuffer = ArrayBuffer[ILoggingEvent]()
          override def append(e: ILoggingEvent): Unit = synchronized {
            eventBuffer += e
          }
          def events: immutable.Seq[ILoggingEvent] = synchronized {
            eventBuffer.to[immutable.Seq]
          }
        }

        // Get the Logback root logger and attach a RecordingAppender
        val rootLogger = LoggerFactory.getLogger(org.slf4j.Logger.ROOT_LOGGER_NAME).asInstanceOf[Logger]
        val appender = new RecordingAppender()
        appender.setContext(rootLogger.getLoggerContext)
        appender.start()
        rootLogger.addAppender(appender)
        block
        rootLogger.detachAppender(appender)
        appender.stop()
        appender.events
      }

      withServerAndConfig()((Action, _) => Action { rh =>
        Results.Ok(rh.headers.get("User-Agent").toString)
      }) { port =>
        def testAgent[R: AsResult](agent: String) = {
          val logMessages = recordLogEvents {
            val Seq(response) = BasicHttpClient.makeRequests(port)(
              BasicRequest("GET", "/", "HTTP/1.1", Map(
                "User-Agent" -> agent
              ), "")
            )
            response.body must beLeft(s"Some($agent)")
          }
          logMessages.map(_.getFormattedMessage) must contain(contain(agent))
        }
        // These agent strings come from https://github.com/playframework/playframework/issues/7997
        testAgent("Mozilla/5.0 (iPhone; CPU iPhone OS 11_0_3 like Mac OS X) AppleWebKit/604.1.38 (KHTML, like Gecko) Mobile/15A432 [FBAN/FBIOS;FBAV/147.0.0.46.81;FBBV/76961488;FBDV/iPhone8,1;FBMD/iPhone;FBSN/iOS;FBSV/11.0.3;FBSS/2;FBCR/T-Mobile.pl;FBID/phone;FBLC/pl_PL;FBOP/5;FBRV/0]")
        testAgent("Mozilla/5.0 (Linux; Android 7.0; TRT-LX1 Build/HUAWEITRT-LX1; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/61.0.3163.98 Mobile Safari/537.36 [FB_IAB/FB4A;FBAV/148.0.0.51.62;]")
        testAgent("Mozilla/5.0 (Linux; Android 7.0; SM-G955F Build/NRD90M; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/62.0.3202.84 Mobile Safari/537.36 [FB_IAB/Orca-Android;FBAV/142.0.0.18.63;]")
      }

    }
  }
}