Tests for metric type mapping config

Co-authored-by: Simon Westphahl <westphahl@gmail.com>
Signed-off-by: Simon Westphahl <simon.westphahl@bmw.de>

mapper_test.go

@@ -302,6 +302,27 @@ mappings:
 - match: test.*.*
   timer_type: wrong
   name: "foo"
+  labels: {}
+    `,
+			configBad: true,
+		},
+		// Config with good metric type.
+		{
+			config: `---
+mappings:
+- match: test.*.*
+  match_metric_type: counter
+  name: "foo"
+  labels: {}
+    `,
+		},
+		// Config with bad metric type matcher.
+		{
+			config: `---
+mappings:
+- match: test.*.*
+  match_metric_type: wrong
+  name: "foo"
   labels: {}
     `,
 			configBad: true,