Add message ID increment test (#81)

uniqid_test.go

@@ -0,0 +1,32 @@
+// Copyright 2020 The mqtt-go authors.
+//
+// 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 mqtt
+
+import (
+	"testing"
+)
+
+func TestBaseClient_IDIncrement(t *testing.T) {
+	c := &BaseClient{idLast: 0xFFFF}
+
+	// 0 is reserved for auto, next to 0xFFFF is 1
+	if id := c.newID(); id != 1 {
+		t.Errorf("Expected newID: 1, got: %d", id)
+	}
+
+	if id := c.newID(); id != 2 {
+		t.Errorf("Expected newID: 2, got: %d", id)
+	}
+}