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clock.go
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clock.go
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/******************************************************************************
*
* Copyright 2023 SAP SE
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
******************************************************************************/
package mock
import (
"time"
)
// Clock is a deterministic clock for unit tests. It starts at the Unix epoch
// and only advances when Clock.StepBy() is called.
type Clock struct {
currentTime int64
listeners []func(time.Time)
}
// NewClock starts a new Clock at the Unix epoch.
func NewClock() *Clock {
return &Clock{currentTime: 0}
}
// AddListener registers a callback that will be called whenever the clock is
// advanced. It will also be called once immediately.
func (c *Clock) AddListener(callback func(time.Time)) {
c.listeners = append(c.listeners, callback)
callback(c.Now())
}
// Now reads the clock. This function can be used as a test double for time.Now().
func (c *Clock) Now() time.Time {
return time.Unix(c.currentTime, 0).UTC()
}
// StepBy advances the clock by the given duration.
func (c *Clock) StepBy(d time.Duration) {
c.currentTime += int64(d / time.Second)
for _, callback := range c.listeners {
callback(c.Now())
}
}