diff --git a/pkg/mapper/mapper_test.go b/pkg/mapper/mapper_test.go
index e00ae8f..ca28897 100644
--- a/pkg/mapper/mapper_test.go
+++ b/pkg/mapper/mapper_test.go
@@ -644,6 +644,26 @@ mappings:
 - match: test.*.*
   match_metric_type: counter
   name: "foo"
+  labels: {}
+    `,
+		},
+		// Config with good metric type observer.
+		{
+			config: `---
+mappings:
+- match: test.*.*
+  match_metric_type: observer
+  name: "foo"
+  labels: {}
+    `,
+		},
+		// Config with good metric type timer.
+		{
+			config: `---
+mappings:
+- match: test.*.*
+  match_metric_type: timer
+  name: "foo"
   labels: {}
     `,
 		},