diff --git a/async/promise.go b/async/promise.go
index a03378a..2d185e7 100644
--- a/async/promise.go
+++ b/async/promise.go
@@ -33,9 +33,10 @@ func New[T any](runnable func(resolve func(T), reject func(error))) *Promise[T]
 	}
 
 	p := &Promise[T]{
-		pending: true,
-		mu:      &sync.Mutex{},
-		wg:      &sync.WaitGroup{},
+		runnable: runnable,
+		pending:  true,
+		mu:       &sync.Mutex{},
+		wg:       &sync.WaitGroup{},
 	}
 
 	defer p.run()
diff --git a/async/promise_test.go b/async/promise_test.go
new file mode 100644
index 0000000..aae62d4
--- /dev/null
+++ b/async/promise_test.go
@@ -0,0 +1,146 @@
+package async
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/duke-git/lancet/v2/internal"
+)
+
+func TestResolve(t *testing.T) {
+	assert := internal.NewAssert(t, "TestResolve")
+
+	p := Resolve("abc")
+
+	assert.Equal("abc", p.result)
+	assert.Equal(false, p.pending)
+}
+
+func TestReject(t *testing.T) {
+	assert := internal.NewAssert(t, "TestReject")
+
+	err := errors.New("error")
+	p := Reject[string](err)
+
+	assert.Equal("error", p.err.Error())
+	assert.Equal(false, p.pending)
+}
+
+func TestThen(t *testing.T) {
+	assert := internal.NewAssert(t, "TestThen")
+
+	p1 := New(func(resolve func(string), reject func(error)) {
+		resolve("abc")
+	})
+
+	p2 := Then(p1, func(data string) string {
+		return data + "de"
+	})
+
+	val, err := p1.Await()
+	assert.IsNil(err)
+	assert.Equal("abc", val)
+
+	val, err = p2.Await()
+	assert.IsNil(err)
+	assert.Equal("abcde", val)
+}
+
+func TestPromise_Then(t *testing.T) {
+	assert := internal.NewAssert(t, "TestPromise_Then")
+
+	p1 := New(func(resolve func(int), reject func(error)) {
+		resolve(1)
+	})
+
+	p2 := p1.Then(func(n int) int {
+		return n + 2
+	})
+
+	val, err := p1.Await()
+	assert.IsNil(err)
+	assert.Equal(1, val)
+
+	val, err = p2.Await()
+	assert.IsNil(err)
+	assert.Equal(3, val)
+}
+
+func TestCatch(t *testing.T) {
+	assert := internal.NewAssert(t, "TestCatch")
+
+	p1 := New(func(resolve func(string), reject func(error)) {
+		err := errors.New("error1")
+		reject(err)
+	})
+
+	p2 := Catch(p1, func(err error) error {
+		e := errors.New("error2")
+		return internal.JoinError(err, e)
+	})
+
+	val, err := p1.Await()
+	assert.Equal("", val)
+	assert.IsNotNil(err)
+	assert.Equal("error1", err.Error())
+
+	val, err = p2.Await()
+
+	assert.Equal("", val)
+	assert.IsNotNil(err)
+	assert.Equal("error1\nerror2", err.Error())
+}
+
+func TestPromise_Catch(t *testing.T) {
+	assert := internal.NewAssert(t, "TestPromise_Catch")
+
+	p1 := New(func(resolve func(string), reject func(error)) {
+		err := errors.New("error1")
+		reject(err)
+	})
+
+	p2 := p1.Catch(func(err error) error {
+		e := errors.New("error2")
+		return internal.JoinError(err, e)
+	})
+
+	val, err := p1.Await()
+	assert.Equal("", val)
+	assert.IsNotNil(err)
+	assert.Equal("error1", err.Error())
+
+	val, err = p2.Await()
+
+	assert.Equal("", val)
+	assert.IsNotNil(err)
+	assert.Equal("error1\nerror2", err.Error())
+}
+
+func TestAll(t *testing.T) {
+	assert := internal.NewAssert(t, "TestPromise_Catch")
+
+	t.Run("AllPromisesFullfilled", func(_ *testing.T) {
+		p1 := New(func(resolve func(string), reject func(error)) {
+			resolve("a")
+		})
+		p2 := New(func(resolve func(string), reject func(error)) {
+			resolve("b")
+		})
+		p3 := New(func(resolve func(string), reject func(error)) {
+			resolve("c")
+		})
+
+		p := All([]*Promise[string]{p1, p2, p3})
+
+		val, err := p.Await()
+		assert.Equal([]string{"a", "b", "c"}, val)
+		assert.IsNil(err)
+	})
+
+	// t.Run("AllPromisesEmpty", func(_ *testing.T) {
+	// 	var empty = []*Promise[any]{}
+	// 	p := All(empty)
+	// 	assert.IsNil(p)
+	// })
+
+}