Add tests for extracting paths from message in lambda batcher (#2757)

* add sqs event ops for batcher lambda

* Apply auto-formatting rules

* oops missing file

* Apply auto-formatting rules

---------

Co-authored-by: Github on behalf of Wellcome Collection <wellcomedigitalplatform@wellcome.ac.uk>

pipeline/relation_embedder/batcher/src/main/scala/weco/pipeline/batcher/LambdaMain.scala

@@ -3,18 +3,18 @@ package weco.pipeline.batcher
 import com.amazonaws.services.lambda.runtime.{Context, RequestHandler}
 import grizzled.slf4j.Logging
 import com.amazonaws.services.lambda.runtime.events.SQSEvent
-import com.amazonaws.services.lambda.runtime.events.SQSEvent.SQSMessage
 import org.apache.pekko.actor.ActorSystem
 import weco.messaging.typesafe.SNSBuilder
 import weco.json.JsonUtil._
 import com.typesafe.config.ConfigFactory
 import weco.typesafe.config.builders.EnrichConfig.RichConfig
 
-import scala.collection.JavaConverters._
 import scala.concurrent.ExecutionContext
 import scala.util.Try
 
 object LambdaMain extends RequestHandler[SQSEvent, String] with Logging {
+  import weco.pipeline.batcher.lib.SQSEventOps._
+
   private val config = ConfigFactory.load("application")
 
   private val downstream = config.getString("batcher.use_downstream") match {
@@ -35,29 +35,13 @@ object LambdaMain extends RequestHandler[SQSEvent, String] with Logging {
 
     PathsProcessor(
       config.requireInt("batcher.max_batch_size"),
-      extractPathsFromEvent(event),
+      event.extractPaths,
       downstream
     )
 
     "Done"
   }
 
-  /** Messages consumed by this Lambda are taken from a queue populated by an
-    * SNS topic. The actual message we are interested in is a String containing
-    * the path. However, the matryoshka-like nature of these things means the
-    * lambda receives
-    *   - an event containing
-    *   - a `Records` list, each Record containing
-    *   - an SQS Message with a JSON body containing
-    *   - an SNS notification containing
-    *   - a `Message`, which is the actual content we want
-    */
-  private def extractPathsFromEvent(event: SQSEvent): List[String] =
-    event.getRecords.asScala.toList.flatMap(extractPathFromMessage)
-
-  private def extractPathFromMessage(message: SQSMessage): Option[String] =
-    ujson.read(message.getBody).obj.get("Message").map(_.toString)
-
   private object SNSDownstream extends Downstream {
     private val msgSender = SNSBuilder
       .buildSNSMessageSender(config, subject = "Sent from batcher")

pipeline/relation_embedder/batcher/src/main/scala/weco/pipeline/batcher/lib/SQSEventOps.scala

@@ -0,0 +1,26 @@
+package weco.pipeline.batcher.lib
+
+import com.amazonaws.services.lambda.runtime.events.SQSEvent
+import com.amazonaws.services.lambda.runtime.events.SQSEvent.SQSMessage
+import scala.collection.JavaConverters._
+
+object SQSEventOps {
+
+  /** Messages consumed by Lambda from SQS are taken from a queue populated by
+    * an SNS topic. The actual message we are interested in is a String
+    * containing the path. However, the matryoshka-like nature of these things
+    * means the lambda receives
+    *   - an event containing
+    *   - a `Records` list, each Record containing
+    *   - an SQS Message with a JSON body containing
+    *   - an SNS notification containing
+    *   - a `Message`, which is the actual content we want
+    */
+  implicit class ExtractPathFromSqsEvent(event: SQSEvent) {
+    def extractPaths: List[String] =
+      event.getRecords.asScala.toList.flatMap(extractPathFromMessage)
+
+    private def extractPathFromMessage(message: SQSMessage): Option[String] =
+      ujson.read(message.getBody).obj.get("Message").flatMap(_.strOpt)
+  }
+}

pipeline/relation_embedder/batcher/src/test/scala/weco/pipeline/batcher/SQSEventOpsTest.scala

@@ -0,0 +1,24 @@
+package weco.pipeline.batcher
+
+import com.amazonaws.services.lambda.runtime.events.SQSEvent
+import com.amazonaws.services.lambda.runtime.events.SQSEvent.SQSMessage
+import org.scalatest.funspec.AnyFunSpec
+import org.scalatest.matchers.should.Matchers
+import scala.collection.JavaConverters._
+
+class SQSEventOpsTest extends AnyFunSpec with Matchers {
+  import lib.SQSEventOps._
+
+  describe("Using the implicit class SQSEventOps") {
+    it("extracts paths from an SQSEvent") {
+      val fakeMessage = new SQSMessage()
+        fakeMessage.setBody("{\"Message\":\"A/C\"}")
+      val fakeSQSEvent = new SQSEvent()
+        fakeSQSEvent.setRecords(List(fakeMessage).asJava)
+
+      val paths = fakeSQSEvent.extractPaths
+
+      paths shouldBe List("A/C")
+    }
+  }
+}