diff --git a/build.sbt b/build.sbt
index fcf4691..1a6788b 100644
--- a/build.sbt
+++ b/build.sbt
@@ -2,7 +2,7 @@ import java.io.{BufferedReader, InputStreamReader}
 
 enablePlugins(JavaAppPackaging)
 
-lazy val xmlCalabashVersion = "2.99.10"
+lazy val xmlCalabashVersion = "2.99.11"
 lazy val jafplVersion = "0.3.83"
 lazy val saxonVersion = "10.6"
 lazy val useSaxonEE = Option(System.getProperty("saxonEdition")).getOrElse("HE") == "EE"
diff --git a/src/main/scala/com/xmlcalabash/XMLCalabash.scala b/src/main/scala/com/xmlcalabash/XMLCalabash.scala
index 267564f..34859d9 100644
--- a/src/main/scala/com/xmlcalabash/XMLCalabash.scala
+++ b/src/main/scala/com/xmlcalabash/XMLCalabash.scala
@@ -276,7 +276,7 @@ class XMLCalabash private(userProcessor: Option[Processor], val configurer: XPro
     // Build the options before compiling in case some of them are statics...
     _options.clear()
     val nsmap = mutable.HashMap.empty[String,String]
-    for (param <- args.parameters) {
+    for (param <- parameters) {
       param match {
         case ns: PipelineNamespace =>
           nsmap.put(ns.prefix, ns.namespace)
@@ -355,7 +355,7 @@ class XMLCalabash private(userProcessor: Option[Processor], val configurer: XPro
 
     val nsmap = mutable.HashMap.empty[String,String]
 
-    for (param <- args.parameters) {
+    for (param <- parameters) {
       param match {
         case ns: PipelineNamespace =>
           nsmap.put(ns.prefix, ns.namespace)
@@ -387,7 +387,7 @@ class XMLCalabash private(userProcessor: Option[Processor], val configurer: XPro
     // To deal with outputs, we have to collate multiple outputs to the same port together.
     // But we also have to check that there's at most one explicit DataConsumer.
     val outputMap = mutable.HashMap.empty[String, ListBuffer[PipelineOutputDocument]]
-    for (opt <- args.parameters collect { case p: PipelineOutputDocument => p }) {
+    for (opt <- parameters collect { case p: PipelineOutputDocument => p }) {
       if (!(outputMap.contains(opt.port))) {
         outputMap.put(opt.port, ListBuffer.empty[PipelineOutputDocument])
       }
diff --git a/src/main/scala/com/xmlcalabash/runtime/BufferingConsumer.scala b/src/main/scala/com/xmlcalabash/testing/BufferingConsumer.scala
similarity index 62%
rename from src/main/scala/com/xmlcalabash/runtime/BufferingConsumer.scala
rename to src/main/scala/com/xmlcalabash/testing/BufferingConsumer.scala
index d3e97dc..501630b 100644
--- a/src/main/scala/com/xmlcalabash/runtime/BufferingConsumer.scala
+++ b/src/main/scala/com/xmlcalabash/testing/BufferingConsumer.scala
@@ -1,27 +1,34 @@
-package com.xmlcalabash.runtime
+package com.xmlcalabash.testing
 
 import com.jafpl.messages.Message
 import com.jafpl.steps.DataConsumer
 import com.xmlcalabash.exceptions.XProcException
 import com.xmlcalabash.messages.XProcItemMessage
 import com.xmlcalabash.model.xxml.XOutput
+import com.xmlcalabash.util.MediaType
 
 import scala.collection.mutable.ListBuffer
 
-class BufferingConsumer(output: XOutput) extends DataConsumer {
+class BufferingConsumer() extends DataConsumer {
   private val _items = ListBuffer.empty[XProcItemMessage]
+  private val _mediaTypes = ListBuffer.empty[MediaType]
 
   def messages: List[XProcItemMessage] = _items.toList
 
+  def mediaTypes: List[MediaType] = _mediaTypes.toList
+  def mediaTypes_=(types: List[MediaType]): Unit = {
+    _mediaTypes.clear()
+    _mediaTypes ++= types
+  }
+
   override def consume(port: String, message: Message): Unit = {
     message match {
       case msg: XProcItemMessage =>
         // Check that the message content type is allowed on the output port
-        val mtypes = output.contentTypes;
         val metadata = msg.metadata;
-        if (mtypes.nonEmpty) {
-          if (!metadata.contentType.allowed(mtypes)) {
-            throw XProcException.xdBadOutputMediaType(metadata.contentType, mtypes, output.location)
+        if (_mediaTypes.nonEmpty) {
+          if (!metadata.contentType.allowed(_mediaTypes.toList)) {
+            throw XProcException.xdBadOutputMediaType(metadata.contentType, _mediaTypes.toList, None)
           }
         }
         _items += msg
diff --git a/src/main/scala/com/xmlcalabash/testing/Tester.scala b/src/main/scala/com/xmlcalabash/testing/Tester.scala
index 712eda2..31f3cb4 100644
--- a/src/main/scala/com/xmlcalabash/testing/Tester.scala
+++ b/src/main/scala/com/xmlcalabash/testing/Tester.scala
@@ -2,8 +2,7 @@ package com.xmlcalabash.testing
 
 import com.xmlcalabash.XMLCalabash
 import com.xmlcalabash.exceptions.TestException
-import com.xmlcalabash.runtime.BufferingConsumer
-import com.xmlcalabash.util.S9Api
+import com.xmlcalabash.util.{PipelineOutputConsumer, S9Api}
 import net.sf.saxon.s9api.{QName, Serializer, XdmNode}
 import org.slf4j.{Logger, LoggerFactory}
 
@@ -37,13 +36,16 @@ class Tester(xmlcalabash: XMLCalabash) {
 
   def run(): TestResult = {
     try {
+      var result: Option[BufferingConsumer] = Some(new BufferingConsumer())
+      xmlcalabash.parameter(new PipelineOutputConsumer("result", result.get))
+
       xmlcalabash.configure()
-      val decl = xmlcalabash.step
-      var result = Option.empty[BufferingConsumer]
 
+      val decl = xmlcalabash.step
       if (decl.outputPorts.contains("result")) {
-        result = Some(new BufferingConsumer(decl.output("result")))
-        xmlcalabash.args.output("result", result.get)
+        result.get.mediaTypes = decl.output("result").contentTypes
+      } else {
+        result = None
       }
 
       xmlcalabash.run()
diff --git a/src/main/scala/com/xmlcalabash/util/MediaType.scala b/src/main/scala/com/xmlcalabash/util/MediaType.scala
index 132fb34..2bf205b 100644
--- a/src/main/scala/com/xmlcalabash/util/MediaType.scala
+++ b/src/main/scala/com/xmlcalabash/util/MediaType.scala
@@ -19,6 +19,7 @@ object MediaType {
   val HTML = new MediaType("text", "html")
   val XHTML = new MediaType("application", "xhtml+xml")
   val ZIP = new MediaType("application", "zip")
+  val PDF = new MediaType("application", "pdf")
   val MULTIPART = new MediaType("multipart", "*")
   val MULTIPART_MIXED = new MediaType("multipart", "mixed")