Fix comma condition and add unit test

pkg/infra/iac3/map_marshaller.go

@@ -30,8 +30,8 @@ func (m TsMap) String() string {
 	i := 0
 	for k, v := range m {
 		buf.WriteString(fmt.Sprintf("%s: %v", k, v))
-		if i <= keys {
-			buf.WriteRune(',')
+		if i < keys-1 {
+			buf.WriteString(", ")
 		}
 		i++
 	}
@@ -44,8 +44,8 @@ func (l TsList) String() string {
 	buf.WriteRune('[')
 	for i, v := range l {
 		fmt.Fprintf(&buf, "%v", v)
-		if i < len(l) {
-			buf.WriteRune(',')
+		if i < len(l)-1 {
+			buf.WriteString(", ")
 		}
 	}
 	buf.WriteRune(']')

pkg/infra/iac3/map_marshaller_test.go

@@ -0,0 +1,65 @@
+package iac3
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestTsMap_String(t *testing.T) {
+	tests := []struct {
+		name string
+		m    TsMap
+		want string
+	}{
+		{
+			name: "empty map",
+			m:    TsMap{},
+			want: "{}",
+		},
+		{
+			name: "map with one entry",
+			m:    TsMap{"foo": "bar"},
+			want: "{foo: bar}",
+		},
+		{
+			name: "map with multiple entries",
+			m:    TsMap{"foo": "bar", "baz": "qux"},
+			want: "{foo: bar, baz: qux}",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.m.String(), tt.want)
+		})
+	}
+}
+
+func TestTsList_String(t *testing.T) {
+	tests := []struct {
+		name string
+		l    TsList
+		want string
+	}{
+		{
+			name: "empty list",
+			l:    TsList{},
+			want: "[]",
+		},
+		{
+			name: "list with one entry",
+			l:    TsList{"foo"},
+			want: "[foo]",
+		},
+		{
+			name: "list with multiple entries",
+			l:    TsList{"foo", "bar"},
+			want: "[foo, bar]",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.l.String(), tt.want)
+		})
+	}
+}