test: add failing test for ignoreWhitespace

tests/IgnoreWhitespaceTest.php

@@ -0,0 +1,55 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Jfcherng\Diff\Test;
+
+use Jfcherng\Diff\DiffHelper;
+use Jfcherng\Diff\Renderer\RendererConstant;
+use PHPUnit\Framework\TestCase;
+
+class IgnoreWhitespaceTest extends TestCase
+{
+
+    public function testIgnoreWhitespaces(): void
+    {
+        $old = <<<'PHP'
+<?php
+
+function foo(\DateTimeImmutable $date)
+{
+    if ($date) {
+        echo 'foo';
+    } else {
+        echo 'bar';
+    }
+}
+PHP;
+        $new = <<<'PHP'
+<?php
+
+function foo(\DateTimeImmutable $date)
+{
+    echo 'foo';
+}
+PHP;
+
+        $diff = DiffHelper::calculate($old, $new, 'Unified', [
+            'ignoreWhitespace' => true,
+        ], [
+            'cliColorization' => RendererConstant::CLI_COLOR_DISABLE,
+        ]);
+        $this->assertSame(<<<'DIFF'
+@@ -2,9 +2,5 @@
+
+ function foo(\DateTimeImmutable $date)
+ {
+-    if ($date) {
+     echo 'foo';
+-    } else {
+-        echo 'bar';
+-    }
+ }
+DIFF, $diff);
+    }
+}