diff --git a/src/main/scala/Handler.scala b/src/main/scala/Handler.scala
index fbdad9f..c17b1d3 100644
--- a/src/main/scala/Handler.scala
+++ b/src/main/scala/Handler.scala
@@ -19,9 +19,9 @@ class Handler
       APIGatewayProxyResponseEvent
     ]
     with Logging with QueryJson {
-  implicit val ec: scala.concurrent.ExecutionContext =
+  private implicit val ec: scala.concurrent.ExecutionContext =
     scala.concurrent.ExecutionContext.global
-  val cql = new Cql()
+  private val cql = new Cql()
 
   def handleRequest(
       event: APIGatewayProxyRequestEvent,
diff --git a/src/test/scala/HandlerTest.scala b/src/test/scala/HandlerTest.scala
new file mode 100644
index 0000000..765e494
--- /dev/null
+++ b/src/test/scala/HandlerTest.scala
@@ -0,0 +1,27 @@
+package cql
+
+import org.scalatest.matchers._
+import org.scalatest.funspec.AnyFunSpec
+import cql.lang.BaseTest
+import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyRequestEvent
+
+class HandlerTest extends AnyFunSpec with should.Matchers {
+  val handler = new Handler()
+
+  def assertIO(input: String, status: Int, output: String) =
+    val request = new APIGatewayProxyRequestEvent().withBody(input)
+
+    val response = handler.handleRequest(request, null)
+
+    response.getBody.contains(output) shouldBe true
+
+  describe("a program") {
+    it("should give a 200 for a valid query") {
+      assertIO("+section:commentisfree", 200, "section=commentisfree")
+    }
+
+    it("should give a 400 for an invalid query") {
+      assertIO("this AND", 200, "There must be a query following 'AND', e.g. this AND that.")
+    }
+  }
+}
diff --git a/src/test/scala/lang/ScannerTest.scala b/src/test/scala/lang/ScannerTest.scala
index e0e8b33..283e2db 100644
--- a/src/test/scala/lang/ScannerTest.scala
+++ b/src/test/scala/lang/ScannerTest.scala
@@ -92,13 +92,13 @@ class ScannerTest extends BaseTest {
       assert(tokens === expectedTokens)
     }
 
-    it("should yield a colon token when a query meta value is incomplete") {
+    it("should yield a query field value token when a query meta value is incomplete") {
       val scanner = new Scanner("""example +tag:""")
       val tokens = scanner.scanTokens
       val expectedTokens = List(
         unquotedStringToken("example"),
         Token(TokenType.QUERY_FIELD_KEY, "+tag", Some("tag"), 8, 11),
-        Token(TokenType.COLON, ":", None, 12, 12),
+        Token(TokenType.QUERY_VALUE, ":", None, 12, 12),
         eofToken(13)
       )
       assert(tokens === expectedTokens)