diff --git a/src/test/scala/cromwell/engine/WorkflowManagerActorSpec.scala b/src/test/scala/cromwell/engine/WorkflowManagerActorSpec.scala
index ee50fe7bdf6..68d3883ded5 100644
--- a/src/test/scala/cromwell/engine/WorkflowManagerActorSpec.scala
+++ b/src/test/scala/cromwell/engine/WorkflowManagerActorSpec.scala
@@ -3,18 +3,18 @@ package cromwell.engine
 import java.util.{Calendar, UUID}
 
 import akka.testkit.TestActorRef
-import cromwell.binding.FullyQualifiedName
 import cromwell.binding.types.WdlStringType
 import cromwell.binding.values.WdlString
-import cromwell.engine.ExecutionStatus.{Done, NotStarted, Running}
+import cromwell.engine.ExecutionStatus.{NotStarted, Running}
 import cromwell.engine.db.DataAccess.WorkflowInfo
-import cromwell.engine.db.{CallStatus, QueryWorkflowExecutionResult, DummyDataAccess}
+import cromwell.engine.db.{DummyDataAccess, QueryWorkflowExecutionResult}
 import cromwell.engine.workflow.WorkflowManagerActor
 import cromwell.engine.workflow.WorkflowManagerActor.{SubmitWorkflow, WorkflowOutputs, WorkflowStatus}
 import cromwell.util.SampleWdl
 import cromwell.util.SampleWdl.HelloWorld
-import cromwell.{engine, CromwellTestkitSpec, binding}
+import cromwell.{CromwellTestkitSpec, binding}
 
+import scala.collection.concurrent.TrieMap
 import scala.concurrent.Future
 
 
@@ -56,8 +56,12 @@ class WorkflowManagerActorSpec extends CromwellTestkitSpec("WorkflowManagerActor
       val dataAccess = new DummyDataAccess() {
         workflows foreach { workflow =>
           val id = workflow.workflowId
-          executionStatuses += (id -> Map("hello.hello" -> (if (id == submitted.workflowId) NotStarted else Running)))
-          symbolStore += (workflow.workflowId -> symbols)
+          val status = if (id == submitted.workflowId) NotStarted else Running
+          executionStatuses(id) = TrieMap("hello.hello" -> status)
+          symbolStore(id) = TrieMap.empty
+          symbols foreach { case(symbolStoreKey, symbolStoreEntry) =>
+            symbolStore(id)(symbolStoreKey) = symbolStoreEntry
+          }
         }
 
         override def getWorkflowsByState(states: Traversable[WorkflowState]): Future[Traversable[WorkflowInfo]] = {
diff --git a/src/test/scala/cromwell/engine/db/DummyDataAccess.scala b/src/test/scala/cromwell/engine/db/DummyDataAccess.scala
index df525700d21..fa49e9a21e9 100644
--- a/src/test/scala/cromwell/engine/db/DummyDataAccess.scala
+++ b/src/test/scala/cromwell/engine/db/DummyDataAccess.scala
@@ -1,21 +1,22 @@
 package cromwell.engine.db
 
 import cromwell.binding.values.WdlValue
-import cromwell.binding.{Call, FullyQualifiedName, WdlNamespace}
+import cromwell.binding.{Call, FullyQualifiedName}
 import cromwell.engine.ExecutionStatus.ExecutionStatus
 import cromwell.engine._
 import cromwell.engine.backend.Backend
 import cromwell.engine.db.DataAccess.WorkflowInfo
 
+import scala.collection.concurrent.TrieMap
 import scala.concurrent.Future
 
 case class DummyDataAccess() extends DataAccess {
 
-  private var workflowStates: Map[WorkflowId, WorkflowState] = Map.empty
+  private val workflowStates: TrieMap[WorkflowId, WorkflowState] = TrieMap.empty
 
-  var executionStatuses: Map[WorkflowId, Map[String, ExecutionStatus]] = Map.empty
+  val executionStatuses: TrieMap[WorkflowId, TrieMap[String, ExecutionStatus]] = TrieMap.empty
 
-  var symbolStore: Map[WorkflowId, Map[SymbolStoreKey, SymbolStoreEntry]] = Map.empty
+  val symbolStore: TrieMap[WorkflowId, TrieMap[SymbolStoreKey, SymbolStoreEntry]] = TrieMap.empty
 
   /**
    * Creates a row in each of the backend-info specific tables for each call in `calls` corresponding to the backend
@@ -25,12 +26,13 @@ case class DummyDataAccess() extends DataAccess {
   override def createWorkflow(workflowInfo: WorkflowInfo, symbols: Traversable[SymbolStoreEntry],
                               calls: Traversable[Call], backend: Backend): Future[Unit] = {
     Future.successful {
-      executionStatuses += (workflowInfo.workflowId -> Map.empty)
-      setStatus(workflowInfo.workflowId, calls map { _.fullyQualifiedName }, ExecutionStatus.NotStarted)
-      val newEntries = symbols map { symbol =>
-        symbol.key -> symbol
+      val id = workflowInfo.workflowId
+      executionStatuses += (id -> TrieMap.empty)
+      symbolStore += (id -> TrieMap.empty)
+      setStatus(id, calls map { _.fullyQualifiedName }, ExecutionStatus.NotStarted)
+      symbols foreach { symbol =>
+        symbolStore(id)(symbol.key) = symbol
       }
-      symbolStore += (workflowInfo.workflowId -> newEntries.toMap)
     }
   }
 
@@ -41,7 +43,9 @@ case class DummyDataAccess() extends DataAccess {
 
   override def setStatus(workflowId: WorkflowId, callFqns: Traversable[FullyQualifiedName], callStatus: CallStatus): Future[Unit] = {
     Future.successful {
-      executionStatuses += (workflowId -> (executionStatuses(workflowId) ++ callFqns.map { _ -> callStatus}.toMap))
+      callFqns foreach { callFqn =>
+        executionStatuses(workflowId)(callFqn) = callStatus
+      }
     }
   }
 
@@ -69,17 +73,15 @@ case class DummyDataAccess() extends DataAccess {
   /** The keys in the Map are locally qualified names. */
   override def setOutputs(workflowId: WorkflowId, call: Call, callOutputs: Map[String, WdlValue]): Future[Unit] = {
     Future.successful {
-      val newOutputs = for {
-        callOutput <- callOutputs
-        entry = SymbolStoreEntry(call.fullyQualifiedName + "." + callOutput._1, callOutput._2, input = false)
-      } yield entry.key -> entry
-
-      symbolStore += (workflowId -> (symbolStore(workflowId) ++ newOutputs))
+      callOutputs foreach { case (name, wdlValue) =>
+        val entry = SymbolStoreEntry(call.fullyQualifiedName + "." + name, wdlValue, input = false)
+        symbolStore(workflowId)(entry.key) = entry
+      }
     }
   }
 
   override def getExecutionStatuses(workflowId: WorkflowId): Future[Map[FullyQualifiedName, CallStatus]] = {
-    Future.successful(executionStatuses(workflowId))
+    Future.successful(executionStatuses(workflowId).toMap)
   }
 
   override def getExecutionBackendInfo(workflowId: WorkflowId, call: Call): Future[CallBackendInfo] = ???