add test for 31

Author: fishercoder1534

src/test/java/com/fishercoder/_31Test.java

@@ -0,0 +1,23 @@
+package com.fishercoder;
+
+import com.fishercoder.common.utils.CommonUtils;
+import com.fishercoder.solutions._31;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class _31Test {
+    private static _31.Solution1 solution1;
+    private static int[] nums;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _31.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        nums = new int[]{1, 2, 3};
+        solution1.nextPermutation(nums);
+        CommonUtils.printArray(nums);
+    }
+}