adds test to cover img without valid src

tests/WP/Images/Application/Image_Content_Extractor_Test.php

@@ -0,0 +1,81 @@
+<?php
+
+namespace Yoast\WP\SEO\Tests\WP\Images\Application;
+
+use Yoast\WP\SEO\Images\Application\Image_Content_Extractor;
+use Yoast\WP\SEO\Tests\WP\TestCase;
+
+/**
+ * Class Image_Content_Extractor_Test.
+ *
+ * @group images
+ *
+ * @coversDefaultClass \Yoast\WP\SEO\Images\Application\Image_Content_Extractor
+ * @covers \Yoast\WP\SEO\Images\Application\Image_Content_Extractor
+ */
+final class Image_Content_Extractor_Test extends TestCase {
+
+	/**
+	 * Represents the instance to test.
+	 *
+	 * @var Image_Content_Extractor
+	 */
+	private $instance;
+
+	/**
+	 * Sets up the test class.
+	 *
+	 * @return void
+	 */
+	public function set_up(): void {
+		parent::set_up();
+		$this->instance = new Image_Content_Extractor();
+	}
+
+	/**
+	 * Data provider fr testing the gather_images_wp function.
+	 *
+	 * @return array<string,array<string,string|array<string,int>>> The test data.
+	 */
+	public function gather_images_wp_provider(): array {
+		return [
+			'no src' => [
+				'content'  => '<img />',
+				'expected' => [],
+			],
+			'typo of src' => [
+				'content'  => "<img srcc='https://link.com/newly-added-in-post' class='wp-image-8' />",
+				'expected' => [],
+			],
+			'no image' => [
+				'content'  => '<h1>Test</h1>',
+				'expected' => [],
+			],
+			'with valid image' => [
+				'content'  => "<img src='https://link.com/newly-added-in-post' class='wp-image-8' />",
+				'expected' => [
+					'https://link.com/newly-added-in-post' => 8,
+				],
+			],
+		];
+	}
+
+	/**
+	 * Tests the build function.
+	 *
+	 * @dataProvider gather_images_wp_provider
+	 *
+	 * @covers ::__construct
+	 * @covers ::gather_images
+	 * @covers ::gather_images_wp
+	 *
+	 * @param string            $content  The content.
+	 * @param array<string,int> $expected The expected result.
+	 *
+	 * @return void
+	 */
+	public function test_gather_images_wp( $content, $expected ) {
+
+		$this->assertEquals( $expected, $this->instance->gather_images( $content ) );
+	}
+}