Add test for limiting query numbers

build.sbt

@@ -55,6 +55,8 @@ doctestDecodeHtmlEntities := true
 doctestWithDependencies := false
 doctestTestFramework := DoctestTestFramework.ScalaTest
 
+parallelExecution in Test := false
+
 homepage := Some(url("https://github.com/guardian/scanamo"))
 licenses := Seq("Apache V2" -> url("http://www.apache.org/licenses/LICENSE-2.0.html"))
 publishMavenStyle := true

src/test/scala/com/gu/scanamo/ScanamoFreeTest.scala

@@ -0,0 +1,64 @@
+package com.gu.scanamo
+
+import java.util
+
+import cats._
+import cats.data.State
+import cats.implicits._
+import com.amazonaws.services.dynamodbv2.model.{AttributeValue, QueryResult, ScanResult}
+import com.gu.scanamo.ops.{BatchGet, BatchWrite, Query, _}
+import org.scalatest.{FunSuite, Matchers}
+
+import scala.collection.convert.decorateAll._
+
+class ScanamoFreeTest extends FunSuite with Matchers {
+  test("only make one call for a limited result") {
+    val limitedScan = ScanamoFree.scanWithLimit[Int]("x", 1)
+
+    val countingInterpreter = new RequestCountingInterpreter()
+
+    val numOps = limitedScan.foldMap(countingInterpreter).runEmptyS.value
+
+    assert(numOps == 1)
+  }
+
+  test("unlimited scan, scans exhaustively") {
+    val limitedScan = ScanamoFree.scan[Int]("x")
+
+    val countingInterpreter = new RequestCountingInterpreter()
+
+    val numOps = limitedScan.foldMap(countingInterpreter).runEmptyS.value
+
+    assert(numOps == 42)
+  }
+}
+
+class RequestCountingInterpreter extends (ScanamoOpsA ~> RequestCountingInterpreter.CountingState) {
+  def apply[A](op: ScanamoOpsA[A]): RequestCountingInterpreter.CountingState[A] = op match {
+    case Put(req) => ???
+    case ConditionalPut(req) => ???
+    case Get(req) => ???
+    case Delete(req) => ???
+    case Scan(req) => State(counter =>
+      if (counter < 42)
+        counter + 1 -> new ScanResult().withLastEvaluatedKey(Map("x" -> DynamoFormat[Int].write(1)).asJava)
+          .withItems(List.fill(Option(req.getLimit).map(_.toInt).getOrElse(50))(
+            new util.HashMap[String, AttributeValue]()): _*)
+      else
+        counter -> new ScanResult().withItems(List.empty[java.util.Map[String, AttributeValue]].asJava)
+    )
+    case Query(req) => State(counter =>
+      if (counter < 42)
+        counter + 1 -> new QueryResult().withLastEvaluatedKey(Map("x" -> DynamoFormat[Int].write(1)).asJava)
+            .withItems(List.fill(req.getLimit)(new util.HashMap[String, AttributeValue]()): _*)
+      else
+        counter -> new QueryResult().withItems(List.empty[java.util.Map[String, AttributeValue]].asJava)
+    )
+    case BatchWrite(req) => ???
+    case BatchGet(req) => ???
+  }
+}
+
+object RequestCountingInterpreter {
+  type CountingState[V] = State[Int, V]
+}