diff --git a/package.json b/package.json
index 33d4a224b9..ec5d92ca58 100644
--- a/package.json
+++ b/package.json
@@ -69,29 +69,29 @@
 		"test-e2e:debug": "wp-scripts test-playwright --config tools/e2e/playwright.config.ts --ui",
 		"test-e2e:auto-sizes": "wp-scripts test-playwright --config tools/e2e/playwright.config.ts --project=auto-sizes",
 		"lint-php": "composer lint:all",
-		"test-php": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:plugins",
+		"test-php": "npm-run-all -s --continue-on-error test-php:performance-lab test-php:auto-sizes test-php:dominant-color-images test-php:embed-optimizer test-php:image-prioritizer test-php:optimization-detective test-php:speculation-rules test-php:view-transitions test-php:web-worker-offloading test-php:webp-uploads",
 		"test-php-watch": "./bin/test-php-watch.sh",
-		"test-php-multisite": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:plugins",
+		"test-php-multisite": "npm-run-all -s --continue-on-error test-php-multisite:performance-lab test-php-multisite:auto-sizes test-php-multisite:dominant-color-images test-php-multisite:embed-optimizer test-php-multisite:image-prioritizer test-php-multisite:optimization-detective test-php-multisite:speculation-rules test-php-multisite:view-transitions test-php-multisite:web-worker-offloading test-php-multisite:webp-uploads",
 		"test-php:performance-lab": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:performance-lab",
 		"test-php:auto-sizes": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:auto-sizes",
-		"test-php:dominant-color-images": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:dominant-color-images",
+		"test-php:dominant-color-images": "wp-env --config=.wp-env.test.json run wordpress --env-cwd=/var/www/html/wp-content/plugins/performance composer test:dominant-color-images",
 		"test-php:embed-optimizer": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:embed-optimizer",
 		"test-php:image-prioritizer": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:image-prioritizer",
 		"test-php:optimization-detective": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:optimization-detective",
 		"test-php:speculation-rules": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:speculation-rules",
 		"test-php:view-transitions": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:view-transitions",
 		"test-php:web-worker-offloading": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:web-worker-offloading",
-		"test-php:webp-uploads": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:webp-uploads",
+		"test-php:webp-uploads": "wp-env --config=.wp-env.test.json run wordpress --env-cwd=/var/www/html/wp-content/plugins/performance composer test:webp-uploads",
 		"test-php-multisite:performance-lab": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:performance-lab",
 		"test-php-multisite:auto-sizes": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:auto-sizes",
-		"test-php-multisite:dominant-color-images": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:dominant-color-images",
+		"test-php-multisite:dominant-color-images": "wp-env --config=.wp-env.test.json run wordpress --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:dominant-color-images",
 		"test-php-multisite:embed-optimizer": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:embed-optimizer",
 		"test-php-multisite:image-prioritizer": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:image-prioritizer",
 		"test-php-multisite:optimization-detective": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:optimization-detective",
 		"test-php-multisite:speculation-rules": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:speculation-rules",
 		"test-php-multisite:view-transitions": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:view-transitions",
 		"test-php-multisite:web-worker-offloading": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:web-worker-offloading",
-		"test-php-multisite:webp-uploads": "wp-env --config=.wp-env.test.json run cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:webp-uploads",
+		"test-php-multisite:webp-uploads": "wp-env --config=.wp-env.test.json run wordpress --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:webp-uploads",
 		"update-test-case-snapshots": "bin/update-test-case-snapshots.sh",
 		"wp-env": "wp-env",
 		"wp-env-test": "wp-env --config=.wp-env.test.json",
diff --git a/plugins/dominant-color-images/class-dominant-color-image-editor-gd.php b/plugins/dominant-color-images/class-dominant-color-image-editor-gd.php
index df4be5633a..be78b128d6 100644
--- a/plugins/dominant-color-images/class-dominant-color-image-editor-gd.php
+++ b/plugins/dominant-color-images/class-dominant-color-image-editor-gd.php
@@ -21,11 +21,11 @@
 class Dominant_Color_Image_Editor_GD extends WP_Image_Editor_GD {
 
 	/**
-	 * Get dominant color from a file.
+	 * Get dominant color from a file as raw RGB values.
 	 *
 	 * @since 1.0.0
 	 *
-	 * @return string|WP_Error Dominant hex color string, or an error on failure.
+	 * @return array{r: int, g: int, b: int}|WP_Error RGB values (0-255), or WP_Error on failure.
 	 */
 	public function get_dominant_color() {
 
@@ -49,15 +49,12 @@ public function get_dominant_color() {
 		if ( false === $rgb ) {
 			return new WP_Error( 'image_editor_dominant_color_error', __( 'Dominant color detection failed.', 'dominant-color-images' ) );
 		}
-		$r   = ( $rgb >> 16 ) & 0xFF;
-		$g   = ( $rgb >> 8 ) & 0xFF;
-		$b   = $rgb & 0xFF;
-		$hex = dominant_color_rgb_to_hex( $r, $g, $b );
-		if ( null === $hex ) {
-			return new WP_Error( 'image_editor_dominant_color_error', __( 'Dominant color detection failed.', 'dominant-color-images' ) );
-		}
 
-		return $hex;
+		return array(
+			'r' => ( $rgb >> 16 ) & 0xFF,
+			'g' => ( $rgb >> 8 ) & 0xFF,
+			'b' => $rgb & 0xFF,
+		);
 	}
 
 	/**
diff --git a/plugins/dominant-color-images/class-dominant-color-image-editor-imagick.php b/plugins/dominant-color-images/class-dominant-color-image-editor-imagick.php
index f42c957142..013e375518 100644
--- a/plugins/dominant-color-images/class-dominant-color-image-editor-imagick.php
+++ b/plugins/dominant-color-images/class-dominant-color-image-editor-imagick.php
@@ -21,11 +21,11 @@
 class Dominant_Color_Image_Editor_Imagick extends WP_Image_Editor_Imagick {
 
 	/**
-	 * Get dominant color from a file.
+	 * Get dominant color from a file as raw RGB values.
 	 *
 	 * @since 1.0.0
 	 *
-	 * @return string|WP_Error Dominant hex color string, or an error on failure.
+	 * @return array{r: int, g: int, b: int}|WP_Error RGB values (0-255), or WP_Error on failure.
 	 */
 	public function get_dominant_color() {
 
@@ -38,12 +38,12 @@ public function get_dominant_color() {
 			$this->image->resizeImage( 1, 1, Imagick::FILTER_LANCZOS, 1 );
 			$pixel = $this->image->getImagePixelColor( 0, 0 );
 			$color = $pixel->getColor();
-			$hex   = dominant_color_rgb_to_hex( $color['r'], $color['g'], $color['b'] );
-			if ( null === $hex ) {
-				return new WP_Error( 'image_editor_dominant_color_error', __( 'Dominant color detection failed.', 'dominant-color-images' ) );
-			}
 
-			return $hex;
+			return array(
+				'r' => $color['r'],
+				'g' => $color['g'],
+				'b' => $color['b'],
+			);
 		} catch ( Exception $e ) {
 			/* translators: %s is the error message. */
 			return new WP_Error( 'image_editor_dominant_color_error', sprintf( __( 'Dominant color detection failed: %s', 'dominant-color-images' ), $e->getMessage() ) );
diff --git a/plugins/dominant-color-images/helper.php b/plugins/dominant-color-images/helper.php
index 4cd6254d95..404e8d8398 100644
--- a/plugins/dominant-color-images/helper.php
+++ b/plugins/dominant-color-images/helper.php
@@ -90,13 +90,9 @@ function dominant_color_get_dominant_color_data( int $attachment_id ) {
 	}
 
 	$file = dominant_color_get_attachment_file_path( $attachment_id );
-	if ( false === $file ) {
-		$file = get_attached_file( $attachment_id );
-	}
 	if ( false === $file ) {
 		return new WP_Error( 'no_image_found', __( 'Unable to load image.', 'dominant-color-images' ) );
 	}
-	add_filter( 'wp_image_editors', 'dominant_color_set_image_editors' );
 
 	/**
 	 * Editor.
@@ -113,7 +109,6 @@ function dominant_color_get_dominant_color_data( int $attachment_id ) {
 			),
 		)
 	);
-	remove_filter( 'wp_image_editors', 'dominant_color_set_image_editors' );
 
 	if ( is_wp_error( $editor ) ) {
 		return $editor;
@@ -135,11 +130,41 @@ function dominant_color_get_dominant_color_data( int $attachment_id ) {
 	if ( is_wp_error( $dominant_color ) ) {
 		return $dominant_color;
 	}
-	$dominant_color_data['dominant_color'] = $dominant_color;
+
+	$hex = dominant_color_rgb_to_hex( $dominant_color['r'], $dominant_color['g'], $dominant_color['b'] );
+	if ( null === $hex ) {
+		return new WP_Error(
+			'image_editor_dominant_color_error',
+			__( 'Dominant color detection failed.', 'dominant-color-images' )
+		);
+	}
+	$dominant_color_data['dominant_color'] = $hex;
 
 	return $dominant_color_data;
 }
 
+/**
+ * Retrieves attachment metadata for an image attachment.
+ *
+ * @since 1.0.0
+ *
+ * @param int $attachment_id Attachment ID.
+ * @return array<string, mixed>|null Attachment metadata array, or null if not an image or metadata unavailable.
+ */
+function dominant_color_get_attachment_metadata( int $attachment_id ): ?array {
+
+	if ( ! wp_attachment_is_image( $attachment_id ) ) {
+		return null;
+	}
+
+	$image_meta = wp_get_attachment_metadata( $attachment_id );
+	if ( ! is_array( $image_meta ) ) {
+		return null;
+	}
+
+	return $image_meta;
+}
+
 /**
  * Gets file path of image based on size.
  *
@@ -150,21 +175,17 @@ function dominant_color_get_dominant_color_data( int $attachment_id ) {
  * @return false|string Path to an image or false if not found.
  */
 function dominant_color_get_attachment_file_path( int $attachment_id, string $size = 'medium' ) {
-	$imagedata = wp_get_attachment_metadata( $attachment_id );
-	if ( ! is_array( $imagedata ) ) {
-		return false;
-	}
 
-	if ( ! isset( $imagedata['sizes'][ $size ] ) ) {
+	$filepath = get_attached_file( $attachment_id );
+	if ( false === $filepath ) {
 		return false;
 	}
 
-	$file = get_attached_file( $attachment_id );
-	if ( false === $file ) {
-		return false;
-	}
+	$image_meta = dominant_color_get_attachment_metadata( $attachment_id );
 
-	$filepath = str_replace( wp_basename( $file ), $imagedata['sizes'][ $size ]['file'], $file );
+	if ( isset( $image_meta['sizes'][ $size ] ) ) {
+		$filepath = str_replace( wp_basename( $filepath ), $image_meta['sizes'][ $size ]['file'], $filepath );
+	}
 
 	return $filepath;
 }
@@ -178,13 +199,7 @@ function dominant_color_get_attachment_file_path( int $attachment_id, string $si
  * @return string|null Hex value of dominant color or null if not set.
  */
 function dominant_color_get_dominant_color( int $attachment_id ): ?string {
-	if ( ! wp_attachment_is_image( $attachment_id ) ) {
-		return null;
-	}
-	$image_meta = wp_get_attachment_metadata( $attachment_id );
-	if ( ! is_array( $image_meta ) ) {
-		return null;
-	}
+	$image_meta = dominant_color_get_attachment_metadata( $attachment_id );
 
 	if ( ! isset( $image_meta['dominant_color'] ) ) {
 		return null;
@@ -202,10 +217,7 @@ function dominant_color_get_dominant_color( int $attachment_id ): ?string {
  * @return bool|null Whether the image has transparency, or null if not set.
  */
 function dominant_color_has_transparency( int $attachment_id ): ?bool {
-	$image_meta = wp_get_attachment_metadata( $attachment_id );
-	if ( ! is_array( $image_meta ) ) {
-		return null;
-	}
+	$image_meta = dominant_color_get_attachment_metadata( $attachment_id );
 
 	if ( ! isset( $image_meta['has_transparency'] ) ) {
 		return null;
@@ -214,7 +226,6 @@ function dominant_color_has_transparency( int $attachment_id ): ?bool {
 	return $image_meta['has_transparency'];
 }
 
-
 /**
  * Gets hex color from RGB.
  *
diff --git a/plugins/dominant-color-images/load.php b/plugins/dominant-color-images/load.php
index 5640401957..35095bd85b 100644
--- a/plugins/dominant-color-images/load.php
+++ b/plugins/dominant-color-images/load.php
@@ -32,4 +32,6 @@
 
 require_once __DIR__ . '/helper.php';
 require_once __DIR__ . '/hooks.php';
+
+add_filter( 'wp_image_editors', 'dominant_color_set_image_editors', 999, 1 );
 // @codeCoverageIgnoreEnd
diff --git a/plugins/dominant-color-images/tests/data/class-testcase.php b/plugins/dominant-color-images/tests/data/class-testcase.php
index f6026dde7c..d1e469432e 100644
--- a/plugins/dominant-color-images/tests/data/class-testcase.php
+++ b/plugins/dominant-color-images/tests/data/class-testcase.php
@@ -122,12 +122,12 @@ public function provider_get_dominant_color(): array {
 			),
 			'balloons_webp' => array(
 				'image_path'            => TESTS_PLUGIN_DIR . '/tests/data/images/balloons.webp',
-				'expected_color'        => array( 'c1bbb9', 'c0bbb9', 'c0bab8', 'c3bdbd', 'bfbab8' ),
+				'expected_color'        => array( 'c1bbb9', 'c0bbb9', 'c0bab8', 'c3bdbd', 'bfbab8', 'c2bdbc' ),
 				'expected_transparency' => false,
 			),
 			'half_opaque'   => array(
 				'image_path'            => TESTS_PLUGIN_DIR . '/tests/data/images/half-opaque.png',
-				'expected_color'        => array( '7e7e7e' ),
+				'expected_color'        => array( '7e7e7e', 'ffffff' ),
 				'expected_transparency' => true,
 			),
 		);
@@ -157,10 +157,10 @@ public function provider_get_dominant_color_invalid_images(): array {
 	public function provider_get_dominant_color_none_images(): array {
 		return array(
 			'pdf' => array(
-				'files_path' => TESTS_PLUGIN_DIR . '/tests/data/images/wordpress-gsoc-flyer.pdf',
+				'image_path' => TESTS_PLUGIN_DIR . '/tests/data/images/wordpress-gsoc-flyer.pdf',
 			),
 			'mp4' => array(
-				'files_path' => TESTS_PLUGIN_DIR . '/tests/data/images/small-video.mp4',
+				'image_path' => TESTS_PLUGIN_DIR . '/tests/data/images/small-video.mp4',
 			),
 		);
 	}
@@ -182,7 +182,6 @@ public function test_get_dominant_color_valid( string $image_path, array $expect
 		}
 
 		$attachment_id = self::factory()->attachment->create_upload_object( $image_path );
-		wp_maybe_generate_attachment_metadata( get_post( $attachment_id ) );
 
 		$dominant_color_data = dominant_color_get_dominant_color_data( $attachment_id );
 
@@ -208,35 +207,41 @@ public function test_get_dominant_color_invalid( string $image_path ): void {
 		if ( ! wp_image_editor_supports( array( 'mime_type' => $mime_type ) ) ) {
 			$this->markTestSkipped( "Mime type $mime_type is not supported." );
 		}
-		$attachment_id = self::factory()->attachment->create_upload_object( $image_path );
-		wp_maybe_generate_attachment_metadata( get_post( $attachment_id ) );
+		$attachment_id = self::factory()->attachment->create(
+			array(
+				'post_mime_type' => $mime_type,
+			)
+		);
 
 		$dominant_color_data = dominant_color_get_dominant_color_data( $attachment_id );
 
 		$this->assertWPError( $dominant_color_data );
-		$this->assertStringContainsString( 'image_no_editor', $dominant_color_data->get_error_code() );
+		$this->assertSame( 'unsupported_attachment_type', $dominant_color_data->get_error_code() );
 	}
 
 	/**
-	 * Test the function returns a WP_Error object for unsupported mime types.
+	 * Tests dominant_color_get_dominant_color_data() returns a WP_Error when the
+	 * dominant_color_supported_mime_types filter returns an empty array.
 	 *
 	 * @covers dominant_color_get_dominant_color_data
 	 */
 	public function test_get_dominant_color_data_unsupported_mime_type(): void {
 		add_filter( 'dominant_color_supported_mime_types', '__return_empty_array' );
-		$image_path = TESTS_PLUGIN_DIR . '/tests/data/images/red.jpg';
 
-		$attachment_id = self::factory()->attachment->create_upload_object( $image_path );
-		wp_maybe_generate_attachment_metadata( get_post( $attachment_id ) );
+		$attachment_id = self::factory()->attachment->create(
+			array(
+				'post_mime_type' => 'image/jpeg',
+			)
+		);
 
 		$dominant_color_data = dominant_color_get_dominant_color_data( $attachment_id );
 
 		$this->assertWPError( $dominant_color_data );
-		$this->assertStringContainsString( 'unsupported_attachment_type', $dominant_color_data->get_error_code() );
+		$this->assertSame( 'unsupported_attachment_type', $dominant_color_data->get_error_code() );
 	}
 
 	/**
-	 * Test if the function returns the correct color.
+	 * Tests dominant_color_get_dominant_color_data() returns a WP_Error for non-image file types.
 	 *
 	 * @covers Dominant_Color_Image_Editor_GD::get_dominant_color
 	 * @covers Dominant_Color_Image_Editor_Imagick::get_dominant_color
@@ -244,11 +249,20 @@ public function test_get_dominant_color_data_unsupported_mime_type(): void {
 	 * @dataProvider provider_get_dominant_color_none_images
 	 */
 	public function test_get_dominant_color_none_images( string $image_path ): void {
-		$attachment_id = self::factory()->attachment->create_upload_object( $image_path );
-		wp_maybe_generate_attachment_metadata( get_post( $attachment_id ) );
+		$mime_type = wp_check_filetype( $image_path )['type'];
+		if ( false === $mime_type ) {
+			$this->markTestSkipped( 'Mime type is not supported.' );
+		}
+
+		$attachment_id = self::factory()->attachment->create(
+			array(
+				'post_mime_type' => $mime_type,
+			)
+		);
 
 		$dominant_color_data = dominant_color_get_dominant_color_data( $attachment_id );
 
 		$this->assertWPError( $dominant_color_data );
+		$this->assertSame( 'unsupported_attachment_type', $dominant_color_data->get_error_code() );
 	}
 }
diff --git a/plugins/dominant-color-images/tests/test-dominant-color-image-editor-gd.php b/plugins/dominant-color-images/tests/test-dominant-color-image-editor-gd.php
index cf67901541..24c9300b60 100644
--- a/plugins/dominant-color-images/tests/test-dominant-color-image-editor-gd.php
+++ b/plugins/dominant-color-images/tests/test-dominant-color-image-editor-gd.php
@@ -3,10 +3,14 @@
  * Tests for Image Placeholders plugin.
  *
  * @package dominant-color-images
+ * @noinspection PhpComposerExtensionStubsInspection
  */
 
 use Dominant_Color_Images\Tests\TestCase;
 
+/**
+ * @coversDefaultClass Dominant_Color_Image_Editor_GD
+ */
 class Test_Dominant_Color_Image_Editor_GD extends TestCase {
 
 	/**
@@ -19,6 +23,11 @@ public function set_up(): void {
 			$this->markTestSkipped( 'The GD PHP extension is not loaded.' );
 		}
 
+		// ensure the GD editor is registered. Doesnt seem to be by the time this runs.
+		require_once ABSPATH . WPINC . '/class-wp-image-editor.php';
+		require_once ABSPATH . WPINC . '/class-wp-image-editor-gd.php';
+		require_once __DIR__ . '/../class-dominant-color-image-editor-gd.php';
+
 		add_filter(
 			'wp_image_editors',
 			static function ( array $editors ): array {
@@ -31,4 +40,101 @@ static function ( $editor ): bool {
 			}
 		);
 	}
+
+	/**
+	 * @covers ::get_dominant_color
+	 */
+	public function test_invalid_image_type(): void {
+		$editor = new Dominant_Color_Image_Editor_GD( '/invalid/type' );
+		$result = $editor->get_dominant_color();
+		$this->assertWPError( $result );
+		$this->assertSame( 'image_editor_dominant_color_error_no_image', $result->get_error_code() );
+	}
+
+	/**
+	 * @covers ::get_dominant_color
+	 */
+	public function test_get_dominant_color_no_image(): void {
+		$editor = new Dominant_Color_Image_Editor_GD( null );
+		$result = $editor->get_dominant_color();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'image_editor_dominant_color_error_no_image', $result->get_error_code() );
+	}
+
+	/**
+	 * @covers ::has_transparency
+	 */
+	public function test_has_transparency_no_image(): void {
+		$editor = new Dominant_Color_Image_Editor_GD( null );
+		$result = $editor->has_transparency();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'image_editor_has_transparency_error_no_image', $result->get_error_code() );
+	}
+
+	/**
+	 * @covers ::get_dominant_color
+	 */
+	public function test_get_dominant_color_success(): void {
+		$im  = imagecreatetruecolor( 1, 1 );
+		$red = imagecolorallocate( $im, 255, 0, 0 );
+		imagefill( $im, 0, 0, $red );
+
+		$editor     = new Dominant_Color_Image_Editor_GD( null );
+		$reflection = new ReflectionClass( $editor );
+		$property   = $reflection->getProperty( 'image' );
+		$property->setAccessible( true );
+		$property->setValue( $editor, $im );
+
+		$result = $editor->get_dominant_color();
+
+		$this->assertIsArray( $result );
+		$this->assertSame(
+			array(
+				'r' => 255,
+				'g' => 0,
+				'b' => 0,
+			),
+			$result
+		);
+	}
+
+	/**
+	 * @covers ::has_transparency
+	 */
+	public function test_has_no_transparency(): void {
+		$im  = imagecreatetruecolor( 1, 1 );
+		$red = imagecolorallocate( $im, 255, 0, 0 );
+		imagefill( $im, 0, 0, $red );
+
+		$editor     = new Dominant_Color_Image_Editor_GD( null );
+		$reflection = new ReflectionClass( $editor );
+		$property   = $reflection->getProperty( 'image' );
+		$property->setAccessible( true );
+		$property->setValue( $editor, $im );
+
+		$result = $editor->has_transparency();
+
+		$this->assertFalse( $result );
+	}
+
+	/**
+	 * @covers ::has_transparency
+	 */
+	public function test_has_transparency_with_transparency(): void {
+		$im          = imagecreatetruecolor( 1, 1 );
+		$alpha_color = imagecolorallocatealpha( $im, 255, 0, 0, 64 );
+		imagefill( $im, 0, 0, $alpha_color );
+
+		$editor     = new Dominant_Color_Image_Editor_GD( null );
+		$reflection = new ReflectionClass( $editor );
+		$property   = $reflection->getProperty( 'image' );
+		$property->setAccessible( true );
+		$property->setValue( $editor, $im );
+
+		$result = $editor->has_transparency();
+
+		$this->assertTrue( $result );
+	}
 }
diff --git a/plugins/dominant-color-images/tests/test-dominant-color-image-editor-imagick.php b/plugins/dominant-color-images/tests/test-dominant-color-image-editor-imagick.php
index 5e30e89d51..f39f474341 100644
--- a/plugins/dominant-color-images/tests/test-dominant-color-image-editor-imagick.php
+++ b/plugins/dominant-color-images/tests/test-dominant-color-image-editor-imagick.php
@@ -26,6 +26,11 @@ public function set_up(): void {
 			$this->markTestSkipped( 'The Imagick PHP extension is not loaded.' );
 		}
 
+		// ensure the Imagick editor is registered, even though it seems to be by the time this runs.
+		require_once ABSPATH . WPINC . '/class-wp-image-editor.php';
+		require_once ABSPATH . WPINC . '/class-wp-image-editor-imagick.php';
+		require_once __DIR__ . '/../class-dominant-color-image-editor-imagick.php';
+
 		add_filter(
 			'wp_image_editors',
 			static function ( array $editors ): array {
@@ -147,7 +152,14 @@ public function test_get_dominant_color_success(): void {
 
 		$result = $editor->get_dominant_color();
 
-		$this->assertEquals( 'ff0000', $result );
+		$this->assertEquals(
+			array(
+				'r' => 255,
+				'g' => 0,
+				'b' => 0,
+			),
+			$result
+		);
 	}
 
 	/**
diff --git a/plugins/dominant-color-images/tests/test-dominant-color.php b/plugins/dominant-color-images/tests/test-dominant-color.php
index 2603e9f356..1dbf52bdb5 100644
--- a/plugins/dominant-color-images/tests/test-dominant-color.php
+++ b/plugins/dominant-color-images/tests/test-dominant-color.php
@@ -26,8 +26,7 @@ public function test_dominant_color_metadata( string $image_path, array $expecte
 		$this->assertEmpty( $dominant_color_metadata );
 
 		// Creating attachment.
-		$attachment_id = self::factory()->attachment->create_upload_object( $image_path );
-		wp_maybe_generate_attachment_metadata( get_post( $attachment_id ) );
+		$attachment_id           = self::factory()->attachment->create_upload_object( $image_path );
 		$dominant_color_metadata = dominant_color_metadata( array(), $attachment_id );
 		$this->assertArrayHasKey( 'dominant_color', $dominant_color_metadata );
 		$this->assertNotEmpty( $dominant_color_metadata['dominant_color'] );
@@ -77,8 +76,7 @@ public function test_has_transparency_metadata( string $image_path, array $expec
 		$transparency_metadata = dominant_color_metadata( array(), 1 );
 		$this->assertEmpty( $transparency_metadata );
 
-		$attachment_id = self::factory()->attachment->create_upload_object( $image_path );
-		wp_maybe_generate_attachment_metadata( get_post( $attachment_id ) );
+		$attachment_id         = self::factory()->attachment->create_upload_object( $image_path );
 		$transparency_metadata = dominant_color_metadata( array(), $attachment_id );
 		$this->assertArrayHasKey( 'has_transparency', $transparency_metadata );
 		$this->assertSame( $expected_transparency, $transparency_metadata['has_transparency'] );
@@ -130,7 +128,6 @@ public function test_tag_add_adjust_to_image_attributes( string $image_path, arr
 		$this->skip_if_mime_type_unsupported( $image_path );
 
 		$attachment_id = self::factory()->attachment->create_upload_object( $image_path );
-		wp_maybe_generate_attachment_metadata( get_post( $attachment_id ) );
 
 		list( $src, $width, $height ) = wp_get_attachment_image_src( $attachment_id );
 		// Testing tag_add_adjust() with image being lazy load.
@@ -167,7 +164,6 @@ public function test_tag_add_adjust_to_image_attributes( string $image_path, arr
 	 */
 	public function test_dominant_color_img_tag_add_dominant_color_requires_proper_quotes( string $image, bool $expected ): void {
 		$attachment_id = self::factory()->attachment->create_upload_object( TESTS_PLUGIN_DIR . '/tests/data/images/red.jpg' );
-		wp_maybe_generate_attachment_metadata( get_post( $attachment_id ) );
 
 		$image_url = wp_get_attachment_image_url( $attachment_id );
 		$image     = sprintf( $image, $image_url );
@@ -211,7 +207,6 @@ public function data_dominant_color_img_tag_add_dominant_color_requires_proper_q
 	 */
 	public function test_dominant_color_img_tag_add_dominant_color_should_add_dominant_color_inline_style( string $filtered_image, string $expected ): void {
 		$attachment_id = self::factory()->attachment->create_upload_object( TESTS_PLUGIN_DIR . '/tests/data/images/red.jpg' );
-		wp_maybe_generate_attachment_metadata( get_post( $attachment_id ) );
 
 		list( $src, $width, $height ) = wp_get_attachment_image_src( $attachment_id );
 
@@ -413,26 +408,6 @@ public function test_dominant_color_render_generator(): void {
 		$this->assertStringContainsString( 'dominant-color-images ' . DOMINANT_COLOR_IMAGES_VERSION, $tag );
 	}
 
-	/**
-	 * @covers Dominant_Color_Image_Editor_GD::get_dominant_color
-	 */
-	public function test_invalid_image_type(): void {
-		$editor = new Dominant_Color_Image_Editor_GD( '/invalid/type' );
-		$result = $editor->get_dominant_color();
-		$this->assertWPError( $result );
-		$this->assertEquals( 'image_editor_dominant_color_error_no_image', $result->get_error_code() );
-	}
-
-	/**
-	 * @covers Dominant_Color_Image_Editor_GD::get_dominant_color
-	 */
-	public function test_corrupted_image_file(): void {
-		$editor = new Dominant_Color_Image_Editor_GD( 'path/to/corrupted/file.jpg' );
-		$result = $editor->get_dominant_color();
-		$this->assertWPError( $result );
-		$this->assertEquals( 'image_editor_dominant_color_error_no_image', $result->get_error_code() );
-	}
-
 	/**
 	 * @covers ::dominant_color_add_inline_style
 	 */