test: Add test cases for Tuple2 (alibaba#1501)

Signed-off-by: yunfeiyanggzq <yunfeiyang@buaa.edu.cn>

sentinel-core/src/main/java/com/alibaba/csp/sentinel/util/function/Tuple2.java

@@ -1,5 +1,7 @@
 package com.alibaba.csp.sentinel.util.function;
 
+import java.util.Objects;
+
 /**
  * A tuple of 2 elements.
  */
@@ -31,11 +33,30 @@ public Tuple2<R2, R1> swap() {
         return new Tuple2<R2, R1>(this.r2, this.r1);
     }
 
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (!(o instanceof Tuple2)) {
+            return false;
+        }
+        Tuple2 that = (Tuple2) o;
+        return Objects.equals(this.r1, that.r1) && Objects.equals(this.r2, that.r2);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = r1 != null ? r1.hashCode() : 0;
+        result = 31 * result + (r2 != null ? r2.hashCode() : 0);
+        return result;
+    }
+
     @Override
     public String toString() {
         return "Tuple2{" +
-            "r1=" + r1 +
-            ", r2=" + r2 +
-            '}';
+                "r1=" + r1 +
+                ", r2=" + r2 +
+                '}';
     }
-}
+}

sentinel-core/src/test/java/com/alibaba/csp/sentinel/util/function/Tuple2Test.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 1999-2019 Alibaba Group Holding Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.alibaba.csp.sentinel.util.function;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class Tuple2Test {
+
+    @Test
+    public void testSwap() {
+        Tuple2 tupleOld = new Tuple2(1, 2);
+        Tuple2 tupleNew = tupleOld.swap();
+        Assert.assertEquals(new Tuple2(2, 1), tupleNew);
+    }
+}