diff --git a/LinqStudy.Test/LinqToObject/SetsTest.cs b/LinqStudy.Test/LinqToObject/SetsTest.cs
index ced4bd1..4feb4fe 100644
--- a/LinqStudy.Test/LinqToObject/SetsTest.cs
+++ b/LinqStudy.Test/LinqToObject/SetsTest.cs
@@ -4,6 +4,8 @@ using System.Collections.Generic;
 using System.Linq;
 using Xunit;
 
+using System.Collections.Immutable;
+
 namespace LinqStudy.Test.LinqToObject
 {
     /// <summary>
@@ -382,35 +384,30 @@ namespace LinqStudy.Test.LinqToObject
         }
         #endregion
 
-        #region Concat
+        #region 串联操作:Concat
+
         ///<summary>
-        /// 串联操作
+        /// Concat：将两个序列合并成一个序列，不去重。与Union不同。
         ///<summary>
-        public class ConcatTest
+        [Fact]
+        public void Concat_Test()
         {
-            ///<summary>
-            /// Concat：将两个序列合并成一个序列，不去重。与Union不同。
-            ///<summary>
-            public void Concat_Test()
-            {
-                List<Person> peoples1 = new List<Person>()
+            List<Person> peoples1 = new List<Person>()
             {
                 new Person(){ Id=2, Name="小龙女", Age=28},
                 new Person(){ Id=4, Name="杨过", Age=32},
             };
 
-                List<Person> peoples2 = new List<Person>()
+            List<Person> peoples2 = new List<Person>()
             {
                 new Person(){ Id=2, Name="小龙女", Age=28},
                 new Person(){ Id=3, Name="云花公主", Age=16},
             };
 
-                var concatAct = peoples1.Concat(peoples2);
+            var concatAct = peoples1.Concat(peoples2);
+            var totalCount = concatAct.Count();
 
-                var totalCount = concatAct.Count();
-
-                Assert.Equal(4, totalCount);
-            }
+            Assert.Equal(4, totalCount);
         }
         #endregion
     }