TASK: Avoid errors if an empty string is parsed

Author: mficzel

src/Lexer.php

@@ -36,7 +36,7 @@ class Lexer
     public function __construct($string)
     {
         $this->string = $string;
-        $this->currentCharacter = $string{0};
+        $this->currentCharacter = ($string !== '') ? $string{0} : null;
         $this->characterPosition = 0;
     }
 

tests/ParserTest.php

@@ -5,6 +5,37 @@
 class ParserTest extends TestCase
 {
 
+    /**
+     * @test
+     */
+    public function shouldParseEmptyCode()
+    {
+        $parser = new Parser('');
+
+        $this->assertEquals(
+            [],
+            $parser->parse()
+        );
+    }
+
+    /**
+     * @test
+     */
+    public function shouldParseBlankCode()
+    {
+        $parser = new Parser('    ');
+
+        $this->assertEquals(
+            [
+                [
+                    'type' => 'text',
+                    'payload' => '    '
+                ]
+            ],
+            $parser->parse()
+        );
+    }
+
     /**
      * @test
      */