Tighten up alpha channel test

Author: Corey McCormick

tests/GeneratorTest.php

@@ -69,6 +69,12 @@ public function test_color_is_set()
         $this->assertEquals(50, $generator->getFill()->getForegroundColor()->toRgb()->getRed());
         $this->assertEquals(75, $generator->getFill()->getForegroundColor()->toRgb()->getGreen());
         $this->assertEquals(100, $generator->getFill()->getForegroundColor()->toRgb()->getBlue());
+
+        $generator = (new Generator)->color(50, 75, 100, 0);
+        $this->assertEquals(0, $generator->getFill()->getForegroundColor()->getAlpha());
+        $this->assertEquals(50, $generator->getFill()->getForegroundColor()->toRgb()->getRed());
+        $this->assertEquals(75, $generator->getFill()->getForegroundColor()->toRgb()->getGreen());
+        $this->assertEquals(100, $generator->getFill()->getForegroundColor()->toRgb()->getBlue());
     }
 
     public function test_background_color_is_set()