@@ -44,7 +44,7 @@ func TestExampleTickerFunc(t *testing.T) {
4444 ctx , cancel := context .WithTimeout (context .Background (), 10 * time .Second )
4545 defer cancel ()
4646
47- mClock := clock .NewMock ()
47+ mClock := clock .NewMock (t )
4848
4949 // Because the ticker is started on a goroutine, we can't immediately start
5050 // advancing the clock, or we will race with the start of the ticker. If we
@@ -76,9 +76,74 @@ func TestExampleTickerFunc(t *testing.T) {
7676 }
7777
7878 // Now that we know the ticker is started, we can advance the time.
79- mClock .Advance (time .Hour ).MustWait (ctx , t )
79+ mClock .Advance (time .Hour ).MustWait (ctx )
8080
8181 if tks := tc .Ticks (); tks != 1 {
8282 t .Fatalf ("expected 1 got %d ticks" , tks )
8383 }
8484}
85+
86+ type exampleLatencyMeasurer struct {
87+ mu sync.Mutex
88+ lastLatency time.Duration
89+ }
90+
91+ func newExampleLatencyMeasurer (ctx context.Context , clk clock.Clock ) * exampleLatencyMeasurer {
92+ m := & exampleLatencyMeasurer {}
93+ clk .TickerFunc (ctx , 10 * time .Second , func () error {
94+ start := clk .Now ()
95+ // m.doSomething()
96+ latency := clk .Since (start )
97+ m .mu .Lock ()
98+ defer m .mu .Unlock ()
99+ m .lastLatency = latency
100+ return nil
101+ })
102+ return m
103+ }
104+
105+ func (m * exampleLatencyMeasurer ) LastLatency () time.Duration {
106+ m .mu .Lock ()
107+ defer m .mu .Unlock ()
108+ return m .lastLatency
109+ }
110+
111+ func TestExampleLatencyMeasurer (t * testing.T ) {
112+ t .Parallel ()
113+
114+ // nolint:gocritic // trying to avoid Coder-specific stuff with an eye toward spinning this out
115+ ctx , cancel := context .WithTimeout (context .Background (), 10 * time .Second )
116+ defer cancel ()
117+
118+ mClock := clock .NewMock (t )
119+ trap := mClock .Trap ().Since ()
120+ defer trap .Close ()
121+
122+ lm := newExampleLatencyMeasurer (ctx , mClock )
123+
124+ w := mClock .Advance (10 * time .Second ) // triggers first tick
125+ c := trap .MustWait (ctx ) // call to Since()
126+ mClock .Advance (33 * time .Millisecond )
127+ c .Release ()
128+ w .MustWait (ctx )
129+
130+ if l := lm .LastLatency (); l != 33 * time .Millisecond {
131+ t .Fatalf ("expected 33ms got %s" , l .String ())
132+ }
133+
134+ // Next tick is in 10s - 33ms, but if we don't want to calculate, we can use:
135+ d , w2 := mClock .AdvanceNext ()
136+ c = trap .MustWait (ctx )
137+ mClock .Advance (17 * time .Millisecond )
138+ c .Release ()
139+ w2 .MustWait (ctx )
140+
141+ expectedD := 10 * time .Second - 33 * time .Millisecond
142+ if d != expectedD {
143+ t .Fatalf ("expected %s got %s" , expectedD .String (), d .String ())
144+ }
145+
146+ if l := lm .LastLatency (); l != 17 * time .Millisecond {
147+ t .Fatalf ("expected 17ms got %s" , l .String ())
148+ }
149+ }
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