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Jun 5, 2024
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chore: add example test case for clock package #13465

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84 changes: 84 additions & 0 deletions clock/example_test.go
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Original file line number Diff line number Diff line change
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package clock_test

import (
"context"
"sync"
"testing"
"time"

"github.com/coder/coder/v2/clock"
)

type exampleTickCounter struct {
ctx context.Context
mu sync.Mutex
ticks int
clock clock.Clock
}

func (c *exampleTickCounter) Ticks() int {
c.mu.Lock()
defer c.mu.Unlock()
return c.ticks
}

func (c *exampleTickCounter) count() {
_ = c.clock.TickerFunc(c.ctx, time.Hour, func() error {
c.mu.Lock()
defer c.mu.Unlock()
c.ticks++
return nil
}, "mytag")
}

func newExampleTickCounter(ctx context.Context, clk clock.Clock) *exampleTickCounter {
tc := &exampleTickCounter{ctx: ctx, clock: clk}
go tc.count()
return tc
}

// TestExampleTickerFunc demonstrates how to test the use of TickerFunc.
func TestExampleTickerFunc(t *testing.T) {
t.Parallel()
// nolint:gocritic // trying to avoid Coder-specific stuff with an eye toward spinning this out
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()

mClock := clock.NewMock()

// Because the ticker is started on a goroutine, we can't immediately start
// advancing the clock, or we will race with the start of the ticker. If we
// win that race, the clock gets advanced _before_ the ticker starts, and
// our ticker will not get a tick.
//
// To handle this, we set a trap for the call to TickerFunc(), so that we
// can assert it has been called before advancing the clock.
trap := mClock.Trap().TickerFunc("mytag")
defer trap.Close()

tc := newExampleTickCounter(ctx, mClock)

// Here, we wait for our trap to be triggered.
call, err := trap.Wait(ctx)
if err != nil {
t.Fatal("ticker never started")
}
// it's good practice to release calls before any possible t.Fatal() calls
// so that we don't leave dangling goroutines waiting for the call to be
// released.
call.Release()
if call.Duration != time.Hour {
t.Fatal("unexpected duration")
}

if tks := tc.Ticks(); tks != 0 {
t.Fatalf("expected 0 got %d ticks", tks)
}

// Now that we know the ticker is started, we can advance the time.
mClock.Advance(time.Hour).MustWait(ctx, t)

if tks := tc.Ticks(); tks != 1 {
t.Fatalf("expected 1 got %d ticks", tks)
}
}