add first two subcommand tests

subcommand_test.go

@@ -0,0 +1,27 @@
+package arg
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// This file contains tests for parse.go but I decided to put them here
+// since that file is getting large
+
+func TestSubcommandNotAStruct(t *testing.T) {
+	var args struct {
+		A string `arg:"subcommand"`
+	}
+	_, err := NewParser(Config{}, &args)
+	assert.Error(t, err)
+}
+
+func TestPositionalAndSubcommandNotAllowed(t *testing.T) {
+	var args struct {
+		A string   `arg:"positional"`
+		B struct{} `arg:"subcommand"`
+	}
+	_, err := NewParser(Config{}, &args)
+	assert.Error(t, err)
+}