Commit 1a2af5f

@@ -5,7 +5,10 @@ type Option[T any] func(T) T
 type Factory[T any] func() T
 
 func New[T any](options ...Option[T]) T {
-	item := Default[T]()
+	return NewWith[T](Default[T](), options...)
+}
+
+func NewWith[T any](item T, options ...Option[T]) T {
 	for _, option := range options {
 		item = option(item)
 	}

@@ -0,0 +1,81 @@
+package x
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type person struct {
+	name string
+	age  int
+}
+
+func withName(name string) Option[*person] {
+	return With(func(person *person) {
+		person.name = name
+	})
+}
+
+func withAge(age int) Option[*person] {
+	return With(func(person *person) {
+		person.age = age
+	})
+}
+
+func TestOption(t *testing.T) {
+	t.Run("New", func(t *testing.T) {
+		t.Run("without options", func(t *testing.T) {
+			item := New[*person]()
+
+			require.NotNil(t, item)
+			assert.Equal(t, "", item.name)
+			assert.Zero(t, item.age)
+		})
+
+		t.Run("with name", func(t *testing.T) {
+			item := New[*person](withName("mo"))
+
+			require.NotNil(t, item)
+			assert.Equal(t, "mo", item.name)
+		})
+
+		t.Run("with age", func(t *testing.T) {
+			item := New[*person](withAge(42))
+
+			require.NotNil(t, item)
+			assert.Equal(t, 42, item.age)
+		})
+	})
+
+	t.Run("NewWith", func(t *testing.T) {
+		t.Run("without options", func(t *testing.T) {
+			p := &person{}
+			item := NewWith[*person](p)
+
+			require.NotNil(t, item)
+			require.Same(t, p, item)
+			assert.Equal(t, "", item.name)
+			assert.Zero(t, item.age)
+		})
+
+		t.Run("with name", func(t *testing.T) {
+			p := &person{}
+			item := NewWith[*person](p, withName("mo"))
+
+			require.NotNil(t, item)
+			require.Same(t, p, item)
+			assert.Equal(t, "mo", item.name)
+		})
+
+		t.Run("with age", func(t *testing.T) {
+			p := &person{}
+			item := NewWith[*person](p, withAge(42))
+
+			require.NotNil(t, item)
+			require.Same(t, p, item)
+			assert.Equal(t, 42, item.age)
+		})
+	})
+}