From 1ac9aaffc8838d8c74a7e99bd3f524c106db3e79 Mon Sep 17 00:00:00 2001
From: Alex Pott <alex.a.pott@googlemail.com>
Date: Mon, 18 Oct 2021 17:39:52 +0100
Subject: [PATCH] Revert "Issue #3239935 by mondrake, andypost, daffie:
 Refactor ToolkitGdTest"

This reverts commit d0c712ad4d7126cc8e3b084b8e6c1d7aac6fc949.
---
 .../KernelTests/Core/Image/ToolkitGdTest.php  | 567 +++++++++---------
 1 file changed, 278 insertions(+), 289 deletions(-)

diff --git a/core/tests/Drupal/KernelTests/Core/Image/ToolkitGdTest.php b/core/tests/Drupal/KernelTests/Core/Image/ToolkitGdTest.php
index 4c238663f36c..4031189c9b17 100644
--- a/core/tests/Drupal/KernelTests/Core/Image/ToolkitGdTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Image/ToolkitGdTest.php
@@ -4,30 +4,18 @@
 
 use Drupal\Core\File\FileSystemInterface;
 use Drupal\Core\Image\ImageInterface;
+use Drupal\Component\Render\FormattableMarkup;
+use Drupal\Core\Site\Settings;
 use Drupal\KernelTests\KernelTestBase;
 
 /**
- * Tests for the GD image toolkit.
+ * Tests that core image manipulations work properly: scale, resize, rotate,
+ * crop, scale and crop, and desaturate.
  *
- * @coversDefaultClass \Drupal\system\Plugin\ImageToolkit\GDToolkit
- * @requires extension gd
  * @group Image
  */
 class ToolkitGdTest extends KernelTestBase {
 
-  /**
-   * Colors that are used in testing.
-   */
-  const BLACK              = [0, 0, 0, 0];
-  const RED                = [255, 0, 0, 0];
-  const GREEN              = [0, 255, 0, 0];
-  const BLUE               = [0, 0, 255, 0];
-  const YELLOW             = [255, 255, 0, 0];
-  const WHITE              = [255, 255, 255, 0];
-  const TRANSPARENT        = [0, 0, 0, 127];
-  const FUCHSIA            = [255, 0, 255, 0];
-  const ROTATE_TRANSPARENT = [255, 255, 255, 127];
-
   /**
    * The image factory service.
    *
@@ -36,14 +24,33 @@ class ToolkitGdTest extends KernelTestBase {
   protected $imageFactory;
 
   /**
-   * A directory where test image files can be saved to.
+   * Colors that are used in testing.
    *
-   * @var string
+   * @var array
    */
-  protected $directory;
+  protected $black       = [0, 0, 0, 0];
+  protected $red         = [255, 0, 0, 0];
+  protected $green       = [0, 255, 0, 0];
+  protected $blue        = [0, 0, 255, 0];
+  protected $yellow      = [255, 255, 0, 0];
+  protected $white       = [255, 255, 255, 0];
+  protected $transparent = [0, 0, 0, 127];
 
   /**
-   * {@inheritdoc}
+   * Used as rotate background colors.
+   *
+   * @var array
+   */
+  protected $fuchsia           = [255, 0, 255, 0];
+  protected $rotateTransparent = [255, 255, 255, 127];
+
+  protected $width = 40;
+  protected $height = 20;
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
    */
   protected static $modules = ['system'];
 
@@ -54,35 +61,36 @@ protected function setUp(): void {
     parent::setUp();
 
     $this->installConfig(['system']);
-
     // Set the image factory service.
     $this->imageFactory = $this->container->get('image.factory');
-    $this->assertEquals('gd', $this->imageFactory->getToolkitId(), 'The image factory is set to use the \'gd\' image toolkit.');
+  }
 
-    // Prepare a directory for test file results.
-    $this->directory = 'public://imagetest';
-    \Drupal::service('file_system')->prepareDirectory($this->directory, FileSystemInterface::CREATE_DIRECTORY);
+  protected function checkRequirements() {
+    // GD2 support is available.
+    if (!function_exists('imagegd2')) {
+      return [
+        'Image manipulations for the GD toolkit cannot run because the GD toolkit is not available.',
+      ];
+    }
+    return parent::checkRequirements();
   }
 
   /**
-   * Assert two colors are equal by RGBA, net of full transparency.
-   *
-   * @param int[] $expected
-   *   The expected RGBA array.
-   * @param int[] $actual
-   *   The actual RGBA array.
-   * @param int $tolerance
-   *   The acceptable difference between the colors.
-   * @param string $message
-   *   The assertion message.
+   * Function to compare two colors by RGBa.
    */
-  protected function assertColorsAreEqual(array $expected, array $actual, int $tolerance, string $message = ''): void {
-    // Fully transparent colors are equal, regardless of RGB.
-    if ($actual[3] == 127 && $expected[3] == 127) {
-      return;
+  public function colorsAreEqual($color_a, $color_b) {
+    // Fully transparent pixels are equal, regardless of RGB.
+    if ($color_a[3] == 127 && $color_b[3] == 127) {
+      return TRUE;
     }
-    $distance = pow(($actual[0] - $expected[0]), 2) + pow(($actual[1] - $expected[1]), 2) + pow(($actual[2] - $expected[2]), 2) + pow(($actual[3] - $expected[3]), 2);
-    $this->assertLessThanOrEqual($tolerance, $distance, $message . " - Actual: {" . implode(',', $actual) . "}, Expected: {" . implode(',', $expected) . "}, Distance: " . $distance . ", Tolerance: " . $tolerance);
+
+    foreach ($color_a as $key => $value) {
+      if ($color_b[$key] != $value) {
+        return FALSE;
+      }
+    }
+
+    return TRUE;
   }
 
   /**
@@ -101,87 +109,123 @@ public function getPixelColor(ImageInterface $image, $x, $y) {
   }
 
   /**
-   * Data provider for ::testManipulations().
+   * Since PHP can't visually check that our images have been manipulated
+   * properly, build a list of expected color values for each of the corners and
+   * the expected height and widths for the final images.
    */
-  public function providerTestImageFiles(): array {
+  public function testManipulations() {
+
+    // Test that the image factory is set to use the GD toolkit.
+    $this->assertEquals('gd', $this->imageFactory->getToolkitId(), 'The image factory is set to use the \'gd\' image toolkit.');
+
+    // Test the list of supported extensions.
+    $expected_extensions = ['png', 'gif', 'jpeg', 'jpg', 'jpe', 'webp'];
+    $supported_extensions = $this->imageFactory->getSupportedExtensions();
+    $this->assertEquals($expected_extensions, array_intersect($expected_extensions, $supported_extensions));
+
+    // Test that the supported extensions map to correct internal GD image
+    // types.
+    $expected_image_types = [
+      'png' => IMAGETYPE_PNG,
+      'gif' => IMAGETYPE_GIF,
+      'jpeg' => IMAGETYPE_JPEG,
+      'jpg' => IMAGETYPE_JPEG,
+      'jpe' => IMAGETYPE_JPEG,
+      'webp' => IMAGETYPE_WEBP,
+    ];
+    $image = $this->imageFactory->get();
+    foreach ($expected_image_types as $extension => $expected_image_type) {
+      $image_type = $image->getToolkit()->extensionToImageType($extension);
+      $this->assertSame($expected_image_type, $image_type);
+    }
+
     // Typically the corner colors will be unchanged. These colors are in the
     // order of top-left, top-right, bottom-right, bottom-left.
-    $default_corners = [static::RED, static::GREEN, static::BLUE, static::TRANSPARENT];
+    $default_corners = [$this->red, $this->green, $this->blue, $this->transparent];
+
+    // A list of files that will be tested.
+    $files = [
+      'image-test.png',
+      'image-test.gif',
+      'image-test-no-transparency.gif',
+      'image-test.jpg',
+      'img-test.webp',
+    ];
 
     // Setup a list of tests to perform on each type.
-    $test_cases = [
+    $operations = [
       'resize' => [
-        'operation' => 'resize',
+        'function' => 'resize',
         'arguments' => ['width' => 20, 'height' => 10],
         'width' => 20,
         'height' => 10,
         'corners' => $default_corners,
       ],
       'scale_x' => [
-        'operation' => 'scale',
+        'function' => 'scale',
         'arguments' => ['width' => 20],
         'width' => 20,
         'height' => 10,
         'corners' => $default_corners,
       ],
       'scale_y' => [
-        'operation' => 'scale',
+        'function' => 'scale',
         'arguments' => ['height' => 10],
         'width' => 20,
         'height' => 10,
         'corners' => $default_corners,
       ],
       'upscale_x' => [
-        'operation' => 'scale',
+        'function' => 'scale',
         'arguments' => ['width' => 80, 'upscale' => TRUE],
         'width' => 80,
         'height' => 40,
         'corners' => $default_corners,
       ],
       'upscale_y' => [
-        'operation' => 'scale',
+        'function' => 'scale',
         'arguments' => ['height' => 40, 'upscale' => TRUE],
         'width' => 80,
         'height' => 40,
         'corners' => $default_corners,
       ],
       'crop' => [
-        'operation' => 'crop',
+        'function' => 'crop',
         'arguments' => ['x' => 12, 'y' => 4, 'width' => 16, 'height' => 12],
         'width' => 16,
         'height' => 12,
-        'corners' => array_fill(0, 4, static::WHITE),
+        'corners' => array_fill(0, 4, $this->white),
       ],
       'scale_and_crop' => [
-        'operation' => 'scale_and_crop',
+        'function' => 'scale_and_crop',
         'arguments' => ['width' => 10, 'height' => 8],
         'width' => 10,
         'height' => 8,
-        'corners' => array_fill(0, 4, static::BLACK),
+        'corners' => array_fill(0, 4, $this->black),
       ],
       'convert_jpg' => [
-        'operation' => 'convert',
+        'function' => 'convert',
         'width' => 40,
         'height' => 20,
         'arguments' => ['extension' => 'jpeg'],
         'corners' => $default_corners,
       ],
       'convert_gif' => [
-        'operation' => 'convert',
+        'function' => 'convert',
         'width' => 40,
         'height' => 20,
         'arguments' => ['extension' => 'gif'],
         'corners' => $default_corners,
       ],
       'convert_png' => [
-        'operation' => 'convert',
+        'function' => 'convert',
         'width' => 40,
         'height' => 20,
         'arguments' => ['extension' => 'png'],
         'corners' => $default_corners,
       ],
       'convert_webp' => [
-        'operation' => 'convert',
+        'function' => 'convert',
         'width' => 40,
         'height' => 20,
         'arguments' => ['extension' => 'webp'],
@@ -189,51 +233,49 @@ public function providerTestImageFiles(): array {
       ],
     ];
 
-    // Systems using non-bundled GD2 may miss imagerotate(). Test if available.
-    if (function_exists('imagerotate')) {
-      $test_cases += [
+    // Systems using non-bundled GD2 don't have imagerotate. Test if available.
+    // @todo Remove the version check once
+    //   https://www.drupal.org/project/drupal/issues/2670966 is resolved.
+    if (function_exists('imagerotate') && (version_compare(phpversion(), '7.0.26') < 0)) {
+      $operations += [
         'rotate_5' => [
-          'operation' => 'rotate',
+          'function' => 'rotate',
           // Fuchsia background.
           'arguments' => ['degrees' => 5, 'background' => '#FF00FF'],
-          // @todo Re-enable dimensions' check once
-          //   https://www.drupal.org/project/drupal/issues/2921123 is resolved.
-          // 'width' => 41,
-          // 'height' => 23,
-          'corners' => array_fill(0, 4, static::FUCHSIA),
-        ],
-        'rotate_transparent_5' => [
-          'operation' => 'rotate',
-          'arguments' => ['degrees' => 5],
-          // @todo Re-enable dimensions' check once
-          //   https://www.drupal.org/project/drupal/issues/2921123 is resolved.
-          // 'width' => 41,
-          // 'height' => 23,
-          'corners' => array_fill(0, 4, static::ROTATE_TRANSPARENT),
+          'width' => 41,
+          'height' => 23,
+          'corners' => array_fill(0, 4, $this->fuchsia),
         ],
         'rotate_90' => [
-          'operation' => 'rotate',
+          'function' => 'rotate',
           // Fuchsia background.
           'arguments' => ['degrees' => 90, 'background' => '#FF00FF'],
           'width' => 20,
           'height' => 40,
-          'corners' => [static::TRANSPARENT, static::RED, static::GREEN, static::BLUE],
+          'corners' => [$this->transparent, $this->red, $this->green, $this->blue],
+        ],
+        'rotate_transparent_5' => [
+          'function' => 'rotate',
+          'arguments' => ['degrees' => 5],
+          'width' => 41,
+          'height' => 23,
+          'corners' => array_fill(0, 4, $this->rotateTransparent),
         ],
         'rotate_transparent_90' => [
-          'operation' => 'rotate',
+          'function' => 'rotate',
           'arguments' => ['degrees' => 90],
           'width' => 20,
           'height' => 40,
-          'corners' => [static::TRANSPARENT, static::RED, static::GREEN, static::BLUE],
+          'corners' => [$this->transparent, $this->red, $this->green, $this->blue],
         ],
       ];
     }
 
-    // Systems using non-bundled GD2 may miss imagefilter(). Test if available.
+    // Systems using non-bundled GD2 don't have imagefilter. Test if available.
     if (function_exists('imagefilter')) {
-      $test_cases += [
+      $operations += [
         'desaturate' => [
-          'operation' => 'desaturate',
+          'function' => 'desaturate',
           'arguments' => [],
           'height' => 20,
           'width' => 40,
@@ -250,220 +292,148 @@ public function providerTestImageFiles(): array {
       ];
     }
 
-    $ret = [];
-    foreach ([
-      'image-test.png',
-      'image-test.gif',
-      'image-test-no-transparency.gif',
-      'image-test.jpg',
-      'img-test.webp',
-    ] as $file_name) {
-      foreach ($test_cases as $test_case => $values) {
-        $operation = $values['operation'];
-        $arguments = $values['arguments'];
-        unset($values['operation'], $values['arguments']);
-        $ret[] = [$file_name, $test_case, $operation, $arguments, $values];
-      }
-    }
+    // Prepare a directory for test file results.
+    $directory = Settings::get('file_public_path') . '/imagetest';
+    \Drupal::service('file_system')->prepareDirectory($directory, FileSystemInterface::CREATE_DIRECTORY);
+
+    foreach ($files as $file) {
+      foreach ($operations as $op => $values) {
+        // Load up a fresh image.
+        $image = $this->imageFactory->get('core/tests/fixtures/files/' . $file);
+        $toolkit = $image->getToolkit();
+        if (!$image->isValid()) {
+          $this->fail(new FormattableMarkup('Could not load image %file.', ['%file' => $file]));
+          continue 2;
+        }
+        $image_original_type = $image->getToolkit()->getType();
 
-    return $ret;
-  }
+        // All images should be converted to truecolor when loaded.
+        $image_truecolor = imageistruecolor($toolkit->getResource());
+        $this->assertTrue($image_truecolor, new FormattableMarkup('Image %file after load is a truecolor image.', ['%file' => $file]));
 
-  /**
-   * Since PHP can't visually check that our images have been manipulated
-   * properly, build a list of expected color values for each of the corners and
-   * the expected height and widths for the final images.
-   *
-   * @dataProvider providerTestImageFiles
-   */
-  public function testManipulations(string $file_name, string $test_case, string $operation, array $arguments, array $expected): void {
-    // Load up a fresh image.
-    $image = $this->imageFactory->get('core/tests/fixtures/files/' . $file_name);
-    $toolkit = $image->getToolkit();
-    $this->assertTrue($image->isValid());
-    $image_original_type = $image->getToolkit()->getType();
+        // Store the original GD resource.
+        $old_res = $toolkit->getResource();
 
-    // All images should be converted to truecolor when loaded.
-    $this->assertTrue(imageistruecolor($toolkit->getResource()), "Image '$file_name' after load is a truecolor image.");
+        // Perform our operation.
+        $image->apply($values['function'], $values['arguments']);
 
-    // Store the original GD resource.
-    if (PHP_VERSION_ID < 80000) {
-      $old_res = $toolkit->getResource();
-    }
+        // If the operation replaced the resource, check that the old one has
+        // been destroyed.
+        $new_res = $toolkit->getResource();
+        if ($new_res !== $old_res) {
+          // @todo In https://www.drupal.org/node/3133236 convert this to
+          //   $this->assertIsNotResource($old_res).
+          $this->assertFalse(is_resource($old_res), new FormattableMarkup("'%operation' destroyed the original resource.", ['%operation' => $values['function']]));
+        }
 
-    // Perform our operation.
-    $image->apply($operation, $arguments);
-
-    // If the operation replaced the resource, check that the old one has
-    // been destroyed.
-    if (PHP_VERSION_ID < 80000) {
-      $new_res = $toolkit->getResource();
-      if ($new_res !== $old_res) {
-        // @todo In https://www.drupal.org/node/3133236 convert this to
-        //   $this->assertIsNotResource($old_res).
-        $this->assertFalse(is_resource($old_res), "'{$operation}' destroyed the original resource.");
-      }
-    }
+        // To keep from flooding the test with assert values, make a general
+        // value for whether each group of values fail.
+        $correct_dimensions_real = TRUE;
+        $correct_dimensions_object = TRUE;
 
-    // Flush Image object to disk storage.
-    $file_path = $this->directory . '/' . $test_case . image_type_to_extension($image->getToolkit()->getType());
-    $image->save($file_path);
-
-    // Check that the both the GD object and the Image object have an accurate
-    // record of the dimensions.
-    if (isset($expected['height']) && isset($expected['width'])) {
-      $this->assertSame($expected['height'], imagesy($toolkit->getResource()), "Image '$file_name' after '$test_case' should have a proper height.");
-      $this->assertSame($expected['width'], imagesx($toolkit->getResource()), "Image '$file_name' after '$test_case' should have a proper width.");
-      $this->assertSame($expected['height'], $image->getHeight(), "Image '$file_name' after '$test_case' should have a proper height.");
-      $this->assertSame($expected['width'], $image->getWidth(), "Image '$file_name' after '$test_case' should have a proper width.");
-    }
+        if (imagesy($toolkit->getResource()) != $values['height'] || imagesx($toolkit->getResource()) != $values['width']) {
+          $correct_dimensions_real = FALSE;
+        }
 
-    // Now check each of the corners to ensure color correctness.
-    foreach ($expected['corners'] as $key => $expected_color) {
-      // The test gif that does not have transparency color set is a
-      // special case.
-      if ($file_name === 'image-test-no-transparency.gif') {
-        if ($test_case == 'desaturate') {
-          // For desaturating, keep the expected color from the test
-          // data, but set alpha channel to fully opaque.
-          $expected_color[3] = 0;
+        // Check that the image object has an accurate record of the dimensions.
+        if ($image->getWidth() != $values['width'] || $image->getHeight() != $values['height']) {
+          $correct_dimensions_object = FALSE;
         }
-        elseif ($expected_color === static::TRANSPARENT) {
-          // Set expected pixel to yellow where the others have
-          // transparent.
-          $expected_color = static::YELLOW;
+
+        $file_path = $directory . '/' . $op . image_type_to_extension($image->getToolkit()->getType());
+        $image->save($file_path);
+
+        $this->assertTrue($correct_dimensions_real, new FormattableMarkup('Image %file after %action action has proper dimensions.', ['%file' => $file, '%action' => $op]));
+        $this->assertTrue($correct_dimensions_object, new FormattableMarkup('Image %file object after %action action is reporting the proper height and width values.', ['%file' => $file, '%action' => $op]));
+
+        // JPEG colors will always be messed up due to compression. So we skip
+        // these tests if the original or the result is in jpeg format.
+        if ($image->getToolkit()->getType() != IMAGETYPE_JPEG && $image_original_type != IMAGETYPE_JPEG) {
+          // Now check each of the corners to ensure color correctness.
+          foreach ($values['corners'] as $key => $corner) {
+            // The test gif that does not have transparency color set is a
+            // special case.
+            if ($file === 'image-test-no-transparency.gif') {
+              if ($op == 'desaturate') {
+                // For desaturating, keep the expected color from the test
+                // data, but set alpha channel to fully opaque.
+                $corner[3] = 0;
+              }
+              elseif ($corner === $this->transparent) {
+                // Set expected pixel to yellow where the others have
+                // transparent.
+                $corner = $this->yellow;
+              }
+            }
+
+            // Get the location of the corner.
+            switch ($key) {
+              case 0:
+                $x = 0;
+                $y = 0;
+                break;
+
+              case 1:
+                $x = $image->getWidth() - 1;
+                $y = 0;
+                break;
+
+              case 2:
+                $x = $image->getWidth() - 1;
+                $y = $image->getHeight() - 1;
+                break;
+
+              case 3:
+                $x = 0;
+                $y = $image->getHeight() - 1;
+                break;
+            }
+            $color = $this->getPixelColor($image, $x, $y);
+            // We also skip the color test for transparency for gif <-> png
+            // conversion. The convert operation cannot handle that correctly.
+            if ($image->getToolkit()->getType() == $image_original_type || $corner != $this->transparent) {
+              $correct_colors = $this->colorsAreEqual($color, $corner);
+              $this->assertTrue($correct_colors, new FormattableMarkup('Image %file object after %action action has the correct color placement at corner %corner.',
+                ['%file' => $file, '%action' => $op, '%corner' => $key]));
+            }
+          }
         }
-      }
 
-      // Get the location of the corner.
-      switch ($key) {
-        case 0:
-          $x = 0;
-          $y = 0;
-          break;
-
-        case 1:
-          $x = $image->getWidth() - 1;
-          $y = 0;
-          break;
-
-        case 2:
-          $x = $image->getWidth() - 1;
-          $y = $image->getHeight() - 1;
-          break;
-
-        case 3:
-          $x = 0;
-          $y = $image->getHeight() - 1;
-          break;
+        // Check that saved image reloads without raising PHP errors.
+        $image_reloaded = $this->imageFactory->get($file_path);
+        $resource = $image_reloaded->getToolkit()->getResource();
       }
-      $actual_color = $this->getPixelColor($image, $x, $y);
+    }
 
-      // If image cannot handle transparent colors, skip the pixel color test.
-      if ($actual_color[3] === 0 && $expected_color[3] === 127) {
+    // Test creation of image from scratch, and saving to storage.
+    foreach ([IMAGETYPE_PNG, IMAGETYPE_GIF, IMAGETYPE_JPEG, IMAGETYPE_WEBP] as $type) {
+      $image = $this->imageFactory->get();
+      $image->createNew(50, 20, image_type_to_extension($type, FALSE), '#ffff00');
+      $file = 'from_null' . image_type_to_extension($type);
+      $file_path = $directory . '/' . $file;
+      $this->assertEquals(50, $image->getWidth(), new FormattableMarkup('Image file %file has the correct width.', ['%file' => $file]));
+      $this->assertEquals(20, $image->getHeight(), new FormattableMarkup('Image file %file has the correct height.', ['%file' => $file]));
+      $this->assertEquals(image_type_to_mime_type($type), $image->getMimeType(), new FormattableMarkup('Image file %file has the correct MIME type.', ['%file' => $file]));
+      $this->assertTrue($image->save($file_path), new FormattableMarkup('Image %file created anew from a null image was saved.', ['%file' => $file]));
+
+      // Reload saved image.
+      $image_reloaded = $this->imageFactory->get($file_path);
+      if (!$image_reloaded->isValid()) {
+        $this->fail(new FormattableMarkup('Could not load image %file.', ['%file' => $file]));
         continue;
       }
-
-      // JPEG has small differences in color after processing.
-      $tolerance = $image_original_type === IMAGETYPE_JPEG ? 3 : 0;
-
-      $this->assertColorsAreEqual($expected_color, $actual_color, $tolerance, "Image '$file_name' object after '$test_case' action has the correct color placement at corner '$key'");
-    }
-
-    // Check that saved image reloads without raising PHP errors.
-    $image_reloaded = $this->imageFactory->get($file_path);
-    if (PHP_VERSION_ID >= 80000) {
-      $this->assertInstanceOf(\GDImage::class, $image_reloaded->getToolkit()->getResource());
-    }
-    else {
-      $this->assertIsResource($image_reloaded->getToolkit()->getResource());
-    }
-  }
-
-  /**
-   * @covers ::getSupportedExtensions
-   * @covers ::extensionToImageType
-   */
-  public function testSupportedExtensions(): void {
-    // Test the list of supported extensions.
-    $expected_extensions = ['png', 'gif', 'jpeg', 'jpg', 'jpe', 'webp'];
-    $this->assertEqualsCanonicalizing($expected_extensions, $this->imageFactory->getSupportedExtensions());
-
-    // Test that the supported extensions map to correct internal GD image
-    // types.
-    $expected_image_types = [
-      'png' => IMAGETYPE_PNG,
-      'gif' => IMAGETYPE_GIF,
-      'jpeg' => IMAGETYPE_JPEG,
-      'jpg' => IMAGETYPE_JPEG,
-      'jpe' => IMAGETYPE_JPEG,
-      'webp' => IMAGETYPE_WEBP,
-    ];
-    $image = $this->imageFactory->get();
-    foreach ($expected_image_types as $extension => $expected_image_type) {
-      $this->assertSame($expected_image_type, $image->getToolkit()->extensionToImageType($extension));
-    }
-  }
-
-  /**
-   * Data provider for ::testCreateImageFromScratch().
-   */
-  public function providerSupportedImageTypes(): array {
-    return [
-      [IMAGETYPE_PNG],
-      [IMAGETYPE_GIF],
-      [IMAGETYPE_JPEG],
-      [IMAGETYPE_WEBP],
-    ];
-  }
-
-  /**
-   * Tests that GD functions for the image type are available.
-   *
-   * @dataProvider providerSupportedImageTypes
-   */
-  public function testGdFunctionsExist(int $type): void {
-    $extension = image_type_to_extension($type, FALSE);
-    $this->assertTrue(function_exists("imagecreatefrom$extension"), "imagecreatefrom$extension should exist.");
-    $this->assertTrue(function_exists("image$extension"), "image$extension should exist.");
-  }
-
-  /**
-   * Tests creation of image from scratch, and saving to storage.
-   *
-   * @dataProvider providerSupportedImageTypes
-   */
-  public function testCreateImageFromScratch(int $type): void {
-    // Build an image from scratch.
-    $image = $this->imageFactory->get();
-    $image->createNew(50, 20, image_type_to_extension($type, FALSE), '#ffff00');
-    $file = 'from_null' . image_type_to_extension($type);
-    $file_path = $this->directory . '/' . $file;
-    $this->assertSame(50, $image->getWidth());
-    $this->assertSame(20, $image->getHeight());
-    $this->assertSame(image_type_to_mime_type($type), $image->getMimeType());
-    $this->assertTrue($image->save($file_path));
-
-    // Reload and check saved image.
-    $image_reloaded = $this->imageFactory->get($file_path);
-    $this->assertTrue($image_reloaded->isValid());
-    $this->assertSame(50, $image_reloaded->getWidth());
-    $this->assertSame(20, $image_reloaded->getHeight());
-    $this->assertSame(image_type_to_mime_type($type), $image_reloaded->getMimeType());
-    if ($image_reloaded->getToolkit()->getType() == IMAGETYPE_GIF) {
-      // Check that image has the correct transparent color channel set.
-      $this->assertSame('#ffff00', $image_reloaded->getToolkit()->getTransparentColor());
-    }
-    else {
-      // Check that image has no color channel set.
-      $this->assertNull($image_reloaded->getToolkit()->getTransparentColor());
+      $this->assertEquals(50, $image_reloaded->getWidth(), new FormattableMarkup('Image file %file has the correct width.', ['%file' => $file]));
+      $this->assertEquals(20, $image_reloaded->getHeight(), new FormattableMarkup('Image file %file has the correct height.', ['%file' => $file]));
+      $this->assertEquals(image_type_to_mime_type($type), $image_reloaded->getMimeType(), new FormattableMarkup('Image file %file has the correct MIME type.', ['%file' => $file]));
+      if ($image_reloaded->getToolkit()->getType() == IMAGETYPE_GIF) {
+        $this->assertEquals('#ffff00', $image_reloaded->getToolkit()->getTransparentColor(), new FormattableMarkup('Image file %file has the correct transparent color channel set.', ['%file' => $file]));
+      }
+      else {
+        $this->assertNull($image_reloaded->getToolkit()->getTransparentColor(), new FormattableMarkup('Image file %file has no color channel set.', ['%file' => $file]));
+      }
     }
-  }
 
-  /**
-   * Tests failures of the 'create_new' operation.
-   */
-  public function testCreateNewFailures(): void {
+    // Test failures of the 'create_new' operation.
     $image = $this->imageFactory->get();
     $image->createNew(-50, 20);
     $this->assertFalse($image->isValid(), 'CreateNew with negative width fails.');
@@ -512,6 +482,10 @@ public function testResourceDestruction() {
    * Tests for GIF images with transparency.
    */
   public function testGifTransparentImages() {
+    // Prepare a directory for test file results.
+    $directory = Settings::get('file_public_path') . '/imagetest';
+    \Drupal::service('file_system')->prepareDirectory($directory, FileSystemInterface::CREATE_DIRECTORY);
+
     // Test loading an indexed GIF image with transparent color set.
     // Color at top-right pixel should be fully transparent.
     $file = 'image-test-transparent-indexed.gif';
@@ -519,20 +493,20 @@ public function testGifTransparentImages() {
     $resource = $image->getToolkit()->getResource();
     $color_index = imagecolorat($resource, $image->getWidth() - 1, 0);
     $color = array_values(imagecolorsforindex($resource, $color_index));
-    $this->assertEquals(static::ROTATE_TRANSPARENT, $color, "Image {$file} after load has full transparent color at corner 1.");
+    $this->assertEquals($this->rotateTransparent, $color, "Image {$file} after load has full transparent color at corner 1.");
 
     // Test deliberately creating a GIF image with no transparent color set.
     // Color at top-right pixel should be fully transparent while in memory,
     // fully opaque after flushing image to file.
     $file = 'image-test-no-transparent-color-set.gif';
-    $file_path = $this->directory . '/' . $file;
+    $file_path = $directory . '/' . $file;
     // Create image.
     $image = $this->imageFactory->get();
     $image->createNew(50, 20, 'gif', NULL);
     $resource = $image->getToolkit()->getResource();
     $color_index = imagecolorat($resource, $image->getWidth() - 1, 0);
     $color = array_values(imagecolorsforindex($resource, $color_index));
-    $this->assertEquals(static::ROTATE_TRANSPARENT, $color, "New GIF image with no transparent color set after creation has full transparent color at corner 1.");
+    $this->assertEquals($this->rotateTransparent, $color, "New GIF image with no transparent color set after creation has full transparent color at corner 1.");
     // Save image.
     $this->assertTrue($image->save($file_path), "New GIF image {$file} was saved.");
     // Reload image.
@@ -557,19 +531,34 @@ public function testGifTransparentImages() {
     // can be loaded correctly.
     $file = 'image-test-transparent-out-of-range.gif';
     $image = $this->imageFactory->get('core/tests/fixtures/files/' . $file);
-    $this->assertTrue($image->isValid());
+    $toolkit = $image->getToolkit();
 
-    // All images should be converted to truecolor when loaded.
-    $this->assertTrue(imageistruecolor($image->getToolkit()->getResource()));
+    if (!$image->isValid()) {
+      $this->fail(new FormattableMarkup('Could not load image %file.', ['%file' => $file]));
+    }
+    else {
+      // All images should be converted to truecolor when loaded.
+      $image_truecolor = imageistruecolor($toolkit->getResource());
+      $this->assertTrue($image_truecolor, new FormattableMarkup('Image %file after load is a truecolor image.', ['%file' => $file]));
+    }
   }
 
   /**
    * Tests calling a missing image operation plugin.
    */
   public function testMissingOperation() {
+
+    // Test that the image factory is set to use the GD toolkit.
+    $this->assertEquals('gd', $this->imageFactory->getToolkitId(), 'The image factory is set to use the \'gd\' image toolkit.');
+
+    // An image file that will be tested.
+    $file = 'image-test.png';
+
     // Load up a fresh image.
-    $image = $this->imageFactory->get('core/tests/fixtures/files/image-test.png');
-    $this->assertTrue($image->isValid());
+    $image = $this->imageFactory->get('core/tests/fixtures/files/' . $file);
+    if (!$image->isValid()) {
+      $this->fail(new FormattableMarkup('Could not load image %file.', ['%file' => $file]));
+    }
 
     // Try perform a missing toolkit operation.
     $this->assertFalse($image->apply('missing_op', []), 'Calling a missing image toolkit operation plugin fails.');
-- 
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