fix flake in weighted random picker (#1561)

Signed-off-by: Nir Rozenbaum <[email protected]>

Author: nirrozenbaum

pkg/epp/scheduling/framework/plugins/picker/picker_test.go

@@ -18,6 +18,7 @@ package picker
 
 import (
 	"context"
+	"math"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -138,8 +139,8 @@ func TestPickMaxScorePicker(t *testing.T) {
 
 func TestPickWeightedRandomPicker(t *testing.T) {
 	const (
-		testIterations = 1000
-		tolerance      = 0.2 // 20% tolerance in [0,1] range
+		testIterations = 10000
+		tolerance      = 0.05 // Verify within tolerance ±5%
 	)
 
 	pod1 := &types.PodMetrics{Pod: &backend.Pod{NamespacedName: k8stypes.NamespacedName{Name: "pod1"}}}
@@ -197,14 +198,14 @@ func TestPickWeightedRandomPicker(t *testing.T) {
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
 			picker := NewWeightedRandomPicker(test.maxPods)
-			selectionCounts := make(map[string]int)
 
-			// Calculate expected probabilities based on scores
+			// Summarize the total score of all pods
 			totalScore := 0.0
 			for _, pod := range test.input {
 				totalScore += pod.Score
 			}
 
+			// Calculate expected probabilities based on scores
 			expectedProbabilities := make(map[string]float64)
 			for _, pod := range test.input {
 				podName := pod.GetPod().NamespacedName.Name
@@ -216,32 +217,27 @@ func TestPickWeightedRandomPicker(t *testing.T) {
 			}
 
 			// Initialize selection counters for each pod
+			selectionCounts := make(map[string]int)
 			for _, pod := range test.input {
 				podName := pod.GetPod().NamespacedName.Name
 				selectionCounts[podName] = 0
 			}
 
 			// Run multiple iterations to gather statistical data
-			for i := 0; i < testIterations; i++ {
+			for range testIterations {
 				result := picker.Pick(context.Background(), types.NewCycleState(), test.input)
 
 				// Count selections for probability analysis
-				if len(result.TargetPods) > 0 {
-					selectedPodName := result.TargetPods[0].GetPod().NamespacedName.Name
-					selectionCounts[selectedPodName]++
-				}
+				selectedPodName := result.TargetPods[0].GetPod().NamespacedName.Name
+				selectionCounts[selectedPodName]++
 			}
 
 			// Verify probability distribution
 			for podName, expectedProb := range expectedProbabilities {
 				actualCount := selectionCounts[podName]
 				actualProb := float64(actualCount) / float64(testIterations)
 
-				toleranceValue := expectedProb * tolerance
-				lowerBound := expectedProb - toleranceValue
-				upperBound := expectedProb + toleranceValue
-
-				if actualProb < lowerBound || actualProb > upperBound {
+				if math.Abs(actualProb-expectedProb) > tolerance {
 					t.Errorf("Pod %s: expected probability %.3f ±%.1f%%, got %.3f (count: %d/%d)",
 						podName, expectedProb, tolerance*100, actualProb, actualCount, testIterations)
 				} else {