test: fixup: follow GNU's diff output

Signed-off-by: Jack Cherng <[email protected]>

Author: jfcherng

tests/IgnoreWhitespaceTest.php

@@ -8,9 +8,13 @@
 use Jfcherng\Diff\Renderer\RendererConstant;
 use PHPUnit\Framework\TestCase;
 
-class IgnoreWhitespaceTest extends TestCase
+/**
+ * @internal
+ *
+ * @coversNothing
+ */
+final class IgnoreWhitespaceTest extends TestCase
 {
-
     public function testIgnoreWhitespaces(): void
     {
         $old = <<<'PHP'
@@ -24,6 +28,7 @@ function foo(\DateTimeImmutable $date)
         echo 'bar';
     }
 }
+
 PHP;
         $new = <<<'PHP'
 <?php
@@ -32,24 +37,29 @@ function foo(\DateTimeImmutable $date)
 {
     echo 'foo';
 }
+
 PHP;
 
-        $diff = DiffHelper::calculate($old, $new, 'Unified', [
-            'ignoreWhitespace' => true,
-        ], [
-            'cliColorization' => RendererConstant::CLI_COLOR_DISABLE,
-        ]);
-        $this->assertSame(<<<'DIFF'
+        $expected = <<<'DIFF'
 @@ -2,9 +2,5 @@
-
+ 
  function foo(\DateTimeImmutable $date)
  {
 -    if ($date) {
-     echo 'foo';
+         echo 'foo';
 -    } else {
 -        echo 'bar';
 -    }
  }
-DIFF, $diff);
+
+DIFF;
+
+        $diff = DiffHelper::calculate($old, $new, 'Unified', [
+            'ignoreWhitespace' => true,
+        ], [
+            'cliColorization' => RendererConstant::CLI_COLOR_DISABLE,
+        ]);
+
+        static::assertSame($expected, $diff);
     }
 }