Issue #1 建立 Double 序列初始版本

src/Helpers/SequenceCalculator/DoubleSequenceCalculator.php

@@ -0,0 +1,28 @@
+<?php
+/**
+ * Created by PhpStorm.
+ * User: mouson
+ * Date: 2017/1/10
+ * Time: 03:44
+ */
+
+namespace Mouson\Helpers\SequenceCalculator;
+
+class DoubleSequenceCalculator implements CalculatorInterface
+{
+
+    /**
+     * @param $value
+     *
+     * @return int|mixed
+     */
+    public function calculate($value)
+    {
+        return ($value * 2);
+    }
+
+    public function getSequenceName()
+    {
+        return 'Double';
+    }
+}

tests/Mouson/Helpers/SequenceCalculator/DoubleSequenceCalculatorTest.php

@@ -0,0 +1,35 @@
+<?php
+namespace Mouson\Helpers\SequenceCalculator;
+
+class DoubleSequenceCalculatorTest extends \PHPUnit_Framework_TestCase
+{
+    public function test_物件產生後應可以取得物件名稱()
+    {
+        /** Arrange */
+        $target = new DoubleSequenceCalculator();
+
+        /** Assume */
+        $expected = 'Double';
+
+        /** Act */
+        $actual = $target->getSequenceName();
+
+        /** Assert */
+        $this->assertEquals($expected, $actual);
+    }
+
+    public function test_測試雙倍數列輸入0應回傳0()
+    {
+        /** Arrange */
+        $target = new DoubleSequenceCalculator();
+        $value  = 0;
+        /** Assume */
+        $expected = 0;
+
+        /** Act */
+        $actual = $target->calculate($value);
+
+        /** Assert */
+        $this->assertEquals($expected, $actual);
+    }
+}