fix(gateway): qualify stepped impairment throughput

gateway/qualification_contract_test.go

@@ -212,26 +212,31 @@ func TestQualificationSixImpairmentProfilesTraverseProductionPath(t *testing.T)
 	}
 }
 
+func TestQualificationLossAndSteppedThroughputBounds(t *testing.T) {
+	profiles := qualificationImpairmentProfiles()
+	for _, profile := range profiles[3:] {
+		observation, err := runQualificationImpairment(t, profile, qualificationMediaProfiles()[0],
+			qualificationImpairmentPacketCount, filepath.Join(t.TempDir(), profile.Name+".csv.gz"))
+		if err != nil {
+			t.Fatalf("%s: %v", profile.Name, err)
+		}
+		if observation.ObservedThroughputKbps <= 0 ||
+			profile.Name == "constrained" && len(observation.CapacityStepObservations) != 2 {
+			t.Fatalf("%s observation = %#v", profile.Name, observation)
+		}
+	}
+}
+
 func TestQualificationUsesPublicQUICAndProductionPacer(t *testing.T) {
 	qualificationTraverseProfiles(t, qualificationMediaProfiles())
-	evidence, err := qualificationPacerEvidence(t, filepath.Join(t.TempDir(), "fairness.csv.gz"), 2*time.Second, 2*time.Second)
+	evidence, err := qualificationPacerEvidence(t, filepath.Join(t.TempDir(), "fairness.csv.gz"), 2*time.Second, 4*time.Second)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if len(evidence.PerFlowBytes) != 8 || len(evidence.CapacitySteps) != 2 ||
-		len(evidence.Series) != 6 || evidence.RawSamplesSHA256 == "" || evidence.JainIndex < 0.99 {
+		len(evidence.Series) != 10 || evidence.RawSamplesSHA256 == "" || evidence.JainIndex < 0.99 {
 		t.Fatalf("pacer evidence = %#v", evidence)
 	}
-}
-
-func TestQualificationCapacityStepsConvergeWithinTenSeconds(t *testing.T) {
-	evidence, err := qualificationPacerEvidence(t, filepath.Join(t.TempDir(), "fairness.csv.gz"), 2*time.Second, 10*time.Second)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if len(evidence.CapacitySteps) != 2 {
-		t.Fatalf("capacity steps = %#v", evidence.CapacitySteps)
-	}
 	for _, step := range evidence.CapacitySteps {
 		if step.Convergence > 10*time.Second || step.MaximumFiveSecond > step.FiveSecondCap*105/100 {
 			t.Fatalf("capacity step = %#v", step)

gateway/qualification_harness_test.go

@@ -1187,8 +1187,17 @@ func runQualificationImpairment(t *testing.T, profile qualificationImpairmentPro
 	observation.ObservedLossPercent = float64(observation.Dropped) * 100 / float64(packetCount)
 	observation.ObservedReorderPercent = float64(observation.ObservedOutOfOrder) * 100 / float64(packetCount)
 	if packetCount >= qualificationImpairmentPacketCount {
-		lowerThroughput := float64(media.BitrateKbps) * (1 - profile.LossPercent/100) * 0.90
+		capacityFactor := 1.0
-		upperThroughput := float64(media.BitrateKbps) * 1.05
+		if len(profile.CapacitySteps) > 0 {
+			inverseRates := 1.0
+			for _, reduction := range profile.CapacitySteps {
+				inverseRates += 100 / float64(100-reduction)
+			}
+			capacityFactor = float64(len(profile.CapacitySteps)+1) / inverseRates
+		}
+		expectedThroughput := float64(media.BitrateKbps) * (1 - profile.LossPercent/100) * capacityFactor
+		lowerThroughput := expectedThroughput * 0.90
+		upperThroughput := expectedThroughput * 1.05
 		if observation.ObservedThroughputKbps < lowerThroughput || observation.ObservedThroughputKbps > upperThroughput {
 			return qualificationImpairmentObservation{}, fmt.Errorf("observed throughput %.2f outside [%.2f,%.2f]", observation.ObservedThroughputKbps, lowerThroughput, upperThroughput)
 		}