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// SPDX-FileCopyrightText: © 2024 Grégoire Duchêne <gduchene@awhk.org>
// SPDX-License-Identifier: ISC
package core_test
import (
"context"
"errors"
"fmt"
"testing"
"time"
"go.awhk.org/core"
)
func TestPromise(s *testing.T) {
t := core.T{T: s}
someError := errors.New("some error")
t.Run("Success", func(t *core.T) {
p := core.NewPromise[int]()
t.AssertErrorIs(nil, p.SucceedWith(1))
t.AssertEqual(1, <-p.Value())
})
t.Run("SuccessThenError", func(t *core.T) {
p := core.NewPromise[int]()
t.AssertErrorIs(nil, p.SucceedWith(1))
t.AssertErrorIs(core.ErrPromiseFulfilled, p.FailWith(someError))
t.AssertEqual(1, <-p.Value())
})
t.Run("Error", func(t *core.T) {
p := core.NewPromise[int]()
t.AssertErrorIs(nil, p.FailWith(someError))
t.AssertErrorIs(someError, <-p.Err())
})
t.Run("ErrorThenSuccess", func(t *core.T) {
p := core.NewPromise[int]()
t.AssertErrorIs(nil, p.FailWith(someError))
t.AssertErrorIs(core.ErrPromiseFulfilled, p.SucceedWith(1))
t.AssertErrorIs(someError, <-p.Err())
})
}
func ExamplePromise() {
p := core.NewPromise[string]()
go func() {
time.Sleep(time.Millisecond)
p.SucceedWith("Hello World!")
}()
select {
case s := <-p.Value():
fmt.Printf("Received %q.\n", s)
case err := <-p.Err():
fmt.Printf("Received an error: %s.\n", err)
}
// Output: Received "Hello World!".
}
func ExamplePromise_withContext() {
var (
ctx, cancel = context.WithTimeout(context.Background(), time.Second)
p = core.NewPromise[string]()
)
defer cancel()
go func() {
time.Sleep(time.Millisecond)
p.FailWith(errors.New("some error"))
}()
select {
case s := <-p.Value():
fmt.Printf("Received %q.\n", s)
case err := <-p.Err():
fmt.Printf("Received an error: %s.\n", err)
case <-ctx.Done():
fmt.Printf("Context was cancelled: %s.\n", ctx.Err())
}
// Output: Received an error: some error.
}
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