Add test for PromQL braces when parsing lists of matchers

Signed-off-by: George Robinson <george.robinson@grafana.com>

cli/util_test.go

@@ -0,0 +1,28 @@
+// Copyright 2023 Prometheus Team
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cli
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestParseMatchers(t *testing.T) {
+	// Should not be able to parse lists of matchers using PromQL syntax.
+	// If you want to do use, should put all matchers in a single string.
+	m, err := parseMatchers([]string{"{foo=bar}"})
+	require.EqualError(t, err, "bad matcher format: {foo=bar}")
+	require.Len(t, m, 0)
+}