Add Contains() to Servers

store/server.go

@@ -44,6 +44,21 @@ func (s Servers) IsReadOnly(id string) (readOnly bool, found bool) {
 	return
 }
 
+// Contains returns whether the given node, as specified by its Raft ID,
+// is a member of the set of servers.
+func (s Servers) Contains(id string) bool {
+	if s == nil || id == "" {
+		return false
+	}
+
+	for _, n := range s {
+		if n != nil && n.ID == id {
+			return true
+		}
+	}
+	return false
+}
+
 func (s Servers) Less(i, j int) bool { return s[i].ID < s[j].ID }
 func (s Servers) Len() int           { return len(s) }
 func (s Servers) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }

store/server_test.go

@@ -64,3 +64,50 @@ func Test_IsReadOnly(t *testing.T) {
 		})
 	}
 }
+
+func Test_Contains(t *testing.T) {
+	testCases := []struct {
+		name     string
+		servers  Servers
+		nodeID   string
+		expected bool
+	}{
+		{
+			name:     "EmptyServers",
+			servers:  nil,
+			nodeID:   "1",
+			expected: false,
+		},
+		{
+			name:     "EmptyNodeID",
+			servers:  Servers(make([]*Server, 1)),
+			nodeID:   "",
+			expected: false,
+		},
+		{
+			name: "NonExistentNode",
+			servers: Servers([]*Server{
+				{ID: "node1", Addr: "localhost:4002", Suffrage: "Voter"},
+			}),
+			nodeID:   "node2",
+			expected: false,
+		},
+		{
+			name: "ExistingNode",
+			servers: Servers([]*Server{
+				{ID: "node1", Addr: "localhost:4002", Suffrage: "Voter"},
+			}),
+			nodeID:   "node1",
+			expected: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			actual := tc.servers.Contains(tc.nodeID)
+			if actual != tc.expected {
+				t.Fatalf("Contains for %s returned %t, expected %t", tc.name, actual, tc.expected)
+			}
+		})
+	}
+}