Add testing case for is_connected(), as per CR feedback

Author: leonidasmi

tests/WP/Dashboard/Infrastructure/Analytics_4/Analytics_4_Adapter_Is_Not_Connected_No_SiteKit_Test.php

@@ -0,0 +1,43 @@
+<?php
+// phpcs:disable Yoast.NamingConventions.NamespaceName.TooLong -- Needed in the folder structure.
+namespace Yoast\WP\SEO\Tests\WP\Dashboard\Infrastructure\Analytics_4;
+
+/**
+ * Test class for the is_connected() method, when Site Kit is not active.
+ *
+ * @group analytics_4_adapter
+ *
+ * @requires PHP >= 7.4
+ *
+ * @covers Yoast\WP\SEO\Dashboard\Infrastructure\Analytics_4\Site_Kit_Analytics_4_Adapter::is_connected
+ *
+ * @phpcs:disable Yoast.NamingConventions.ObjectNameDepth.MaxExceeded
+ */
+final class Analytics_4_Adapter_Is_Not_Connected_No_SiteKit_Test extends Abstract_Analytics_4_Adapter_Test {	
+
+	/**
+	 * Let's not activate the Site Kit plugin for this test.
+	 *
+	 * @var string
+	 */
+	public $prereq_plugin_basename = '';
+
+	/**
+	 * Tests is_connected() returns false when Site Kit is not active, even if all the right values are in the DB.
+	 *
+	 * @return void
+	 */
+	public function test_is_not_connected() {
+		$analytics_4_settings = [
+			'accountID'       => '123456789',
+			'propertyID'      => '12345',
+			'webDataStreamID' => '1234',
+			'measurementID'   => 'G-123456789',
+		];
+		\update_option( 'googlesitekit_analytics-4_settings', $analytics_4_settings );
+
+		$is_connected = $this->instance->is_connected();
+
+		$this->assertFalse( $is_connected );
+	}
+}