basic predictor test

certexchange/polling/predictor_test.go

@@ -0,0 +1,60 @@
+package polling
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestPredictor(t *testing.T) {
+	p := newPredictor(time.Second, 30*time.Second, 120*time.Second)
+
+	// Progress of 1 shouldn't update anything.
+	require.Equal(t, 30*time.Second, p.update(1))
+	require.Equal(t, 30*time.Second, p.update(1))
+
+	// Progress of 0 should predict the same interval, then twice that, etc.
+	require.Equal(t, 30*time.Second, p.update(0))
+	require.Equal(t, 60*time.Second, p.update(0))
+
+	// After that, the intervalA should increase slightly.
+	intervalA := p.update(1)
+	require.Less(t, 30*time.Second, intervalA)
+	require.Greater(t, 40*time.Second, intervalA)
+
+	// If the interval is too large, it should decrease, but not by as much because we're
+	// switching direction.
+	intervalB := p.update(2)
+	require.Less(t, 30*time.Second, intervalB)
+	require.Greater(t, intervalA, intervalB)
+
+	// It should keep getting smaller.
+	intervalC := p.update(2)
+	require.Greater(t, intervalB, intervalC)
+
+	// Until we stabilize.
+	require.Equal(t, intervalC, p.update(1))
+
+	// We should always stay above the minimum.
+	for i := 0; i < 100; i++ {
+		require.LessOrEqual(t, time.Second, p.update(2))
+	}
+	require.Equal(t, time.Second, p.update(1))
+
+	// And below the maximum (unless backing off).
+	for i := 0; i < 100; i++ {
+		require.GreaterOrEqual(t, 120*time.Second, p.update(0))
+		require.GreaterOrEqual(t, 120*time.Second, p.update(1))
+	}
+	require.Equal(t, 120*time.Second, p.update(1))
+
+	// But backoff should go much higher.
+	for i := 0; i < 100; i++ {
+		require.GreaterOrEqual(t, 10*120*time.Second, p.update(0))
+	}
+	require.Equal(t, 10*120*time.Second, p.update(0))
+
+	// And revert to the old time when done.
+	require.Equal(t, 120*time.Second, p.update(1))
+}