ensure *taskMetadata type returned from GetTaskMetadataProvider has a…

… stable interface going forward

loadtester/task_metadata.go

@@ -61,18 +61,6 @@ func injectTaskMetadataProvider(ctx context.Context, tm *taskMetadata) context.C
 	return context.WithValue(ctx, taskMetadataCtxKey{}, tm)
 }
 
-type taskMetadataProvider interface {
-	IntervalID() time.Time
-	EnqueueTime() time.Time
-	DequeueTime() time.Time
-	SampleSize() int
-	NumIntervalTasks() int
-	Lag() time.Duration
-}
-
-// TODO: move to unit test
-var _ taskMetadataProvider = (*taskMetadata)(nil)
-
 // GetTaskMetadataProvider returns a possibly nil value that implements:
 //
 // - `IntervalID() time.Time`

loadtester/task_metadata_test.go

@@ -0,0 +1,53 @@
+package loadtester
+
+import (
+	"testing"
+	"time"
+)
+
+func TestMetadataProviderInterfaceStability(t *testing.T) {
+	type taskMetadataProvider interface {
+		IntervalID() time.Time
+		EnqueueTime() time.Time
+		DequeueTime() time.Time
+		SampleSize() int
+		NumIntervalTasks() int
+		Lag() time.Duration
+	}
+
+	now := time.Now()
+	v := taskMetadataProvider(&taskMetadata{taskMetadataState{
+		meta: taskMeta{
+			IntervalID:       now,
+			SampleSize:       2,
+			NumIntervalTasks: 3,
+			Lag:              2 * time.Second,
+		},
+		enqueueTime: now.Add(1 * time.Minute),
+		dequeueTime: now.Add(2 * time.Minute),
+	}})
+
+	if !v.IntervalID().Equal(now) {
+		t.Fatal()
+	}
+
+	if !v.EnqueueTime().Equal(now.Add(1 * time.Minute)) {
+		t.Fatal()
+	}
+
+	if !v.DequeueTime().Equal(now.Add(2 * time.Minute)) {
+		t.Fatal()
+	}
+
+	if v.SampleSize() != 2 {
+		t.Fatal()
+	}
+
+	if v.NumIntervalTasks() != 3 {
+		t.Fatal()
+	}
+
+	if v.Lag() != 2*time.Second {
+		t.Fatal()
+	}
+}