add Attribute definition

Updates #2.

Assets/Tests/AttributeTest.cs

@@ -0,0 +1,25 @@
+using System.Collections;
+using System.Collections.Generic;
+using NUnit.Framework;
+using UnityEngine;
+using UnityEngine.TestTools;
+
+public class AttributeTest
+{
+    [Test]
+    [TestCase(1000000, 0, 0, 0, 0, ExpectedResult = 1000000)]
+    [TestCase(1000000, 1, 0, 0, 0, ExpectedResult = 1000001)]
+    [TestCase(1000000, 0, 2, 0, 0, ExpectedResult = 1000002)]
+    [TestCase(1000000, 0, 0, 10000, 0, ExpectedResult = 2000000)]
+    [TestCase(1000000, 0, 0, 0, 3, ExpectedResult = 1000003)]
+    [TestCase(0, 1000000, 1000000, 5000, 1000, ExpectedResult = 3001000)]
+    [TestCase(1000000, 0, 0, -10000, 0, ExpectedResult = 0)]
+    [TestCase(1000000, 0, 0, -20000, 0, ExpectedResult = 0)]
+    [TestCase(1000000, 0, 0, -20000, 50, ExpectedResult = 0)]
+    public long Calc(long startStat, long levelUp, long baseBonus, long permyriadBonus, long flatBonus)
+    {
+        var attr = new Attribute(startStat);
+        attr.LevelUp(levelUp);
+        return attr.Calc(baseBonus, permyriadBonus, flatBonus);
+    }
+}

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@@ -0,0 +1,11 @@
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Assets/Tests/Tests.asmdef

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+{
+    "name": "Tests",
+    "rootNamespace": "",
+    "references": [
+        "UnityEngine.TestRunner",
+        "UnityEditor.TestRunner",
+        "IdleSurvivors"
+    ],
+    "includePlatforms": [
+        "Editor"
+    ],
+    "excludePlatforms": [],
+    "allowUnsafeCode": false,
+    "overrideReferences": true,
+    "precompiledReferences": [
+        "nunit.framework.dll"
+    ],
+    "autoReferenced": false,
+    "defineConstraints": [
+        "UNITY_INCLUDE_TESTS"
+    ],
+    "versionDefines": [],
+    "noEngineReferences": false
+}

Assets/Tests/Tests.asmdef.meta

@@ -0,0 +1,7 @@
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