49 lines
1.4 KiB
Go
49 lines
1.4 KiB
Go
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package testingx
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import (
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"sync"
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"time"
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)
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// TimeDeterministic implements time.Now in a deterministic fashion
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// such that every time.Time call returns a moment in time that occurs
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// one second after the configured zeroTime.
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//
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// It's safe to use this struct from multiple goroutine contexts.
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type TimeDeterministic struct {
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// counter counts the number of "ticks" passed since the zero time: each
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// call to Now increments this counter by one second.
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counter time.Duration
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// mu protects fields in this structure from concurrent access.
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mu sync.Mutex
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// zeroTime is the lazy-initialized zero time. The first call to Now
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// will initialize this field with the current time.
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zeroTime time.Time
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}
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// NewTimeDeterministic creates a new instance using the given zeroTime value.
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func NewTimeDeterministic(zeroTime time.Time) *TimeDeterministic {
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return &TimeDeterministic{
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counter: 0,
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mu: sync.Mutex{},
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zeroTime: zeroTime,
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}
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}
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// Now is like time.Now but more deterministic. The first call returns the
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// configured zeroTime and subsequent calls return moments in time that occur
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// exactly one second after the time returned by the previous call.
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func (td *TimeDeterministic) Now() time.Time {
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td.mu.Lock()
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if td.zeroTime.IsZero() {
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td.zeroTime = time.Now()
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}
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offset := td.counter
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td.counter += time.Second
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res := td.zeroTime.Add(offset)
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td.mu.Unlock()
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return res
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}
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