fix masterelection_test to force master transitions

masterelection/masterelection_test.go

@@ -2,7 +2,9 @@ package masterelection
 
 import (
 	"fmt"
+	"log"
 	"math/rand"
+	"os"
 	"testing"
 	"time"
 
@@ -26,7 +28,9 @@ func countMasters(nodes []*MasterElection) int {
 func verifyMasterData(t *testing.T, nodes []*MasterElection) {
 	tmp := make(map[string]struct{})
 	for _, n := range nodes {
-		tmp[n.GetMasterData()] = struct{}{}
+		if n != nil {
+			tmp[n.GetMasterData()] = struct{}{}
+		}
 	}
 	if len(tmp) != 1 {
 		t.Errorf("master data propagation error: >1 values: %v", tmp)
@@ -49,18 +53,36 @@ func TestMasterElection(t *testing.T) {
 			fmt.Sprintf("%d", i),
 			1,
 			nil)
-		m.LogPrefix = fmt.Sprintf("node%d: masterelection", i+1)
+		m.Log = log.New(os.Stderr, fmt.Sprintf("node%d: masterelection: ", i+1), 0)
 		go m.Run(stopCh)
 		nodes = append(nodes, m)
 		stop = append(stop, stopCh)
 	}
 
+	// Force master transitions by shutting down the nodes one by
+	// one as the become the master, and verify that there is a
+	// single master among the remaining ones.
 	for i := 0; i < n; i++ {
 		time.Sleep(100 * time.Millisecond)
-		if nm := countMasters(nodes[i:len(nodes)]); nm != 1 {
-			t.Errorf("@%d: masters=%d (expected <= 1)", i, nm)
+
+		masterIdx := -1
+		numMasters := 0
+		for i, m := range nodes {
+			if m == nil {
+				continue
+			}
+			if m.IsMaster() {
+				numMasters++
+				masterIdx = i
+			}
 		}
-		verifyMasterData(t, nodes[i:len(nodes)])
-		close(stop[i])
+
+		if numMasters != 1 {
+			t.Fatalf("masters=%d (expected 1): %#v", numMasters, nodes)
+		}
+		verifyMasterData(t, nodes)
+
+		close(stop[masterIdx])
+		nodes[masterIdx] = nil
 	}
 }