videocore: add simple unit test

This is primarily to confirm that this works around a bug in rsc.io/gt.

host/videocore/videocore_test.go

@@ -0,0 +1,27 @@
+// Copyright 2017 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package videocore
+
+import "testing"
+
+func TestGenPacket(t *testing.T) {
+	actual := genPacket(10, 12, 1, 2, 3)
+	expected := []uint32{0x24, 0x0, 0xa, 0xc, 0xc, 0x1, 0x2, 0x3, 0x0}
+	if !uint32Equals(actual, expected) {
+		t.Fatal(actual)
+	}
+}
+
+func uint32Equals(a []uint32, b []uint32) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i, v := range a {
+		if v != b[i] {
+			return false
+		}
+	}
+	return true
+}