Use a new object for testing Admin_Settings::get_setting().

tests/AdminSettings/AdminSettings_GetSettingTest.php

@@ -11,29 +11,16 @@
  * @covers \AspireUpdate\Admin_Settings::get_setting
  */
 class AdminSettings_GetSettingTest extends WP_UnitTestCase {
-	/**
-	 * Shared instance of the class.
-	 *
-	 * @var \AspireUpdate\Admin_Settings
-	 */
-	private static $instance;
-
-	/**
-	 * Set up before any tests run.
-	 */
-	public static function set_up_before_class() {
-		self::$instance = \AspireUpdate\Admin_Settings::get_instance();
-	}
-
 	/**
 	 * Test that the default 'api_host' value is retrieved.
 	 * 
 	 * @covers \AspireUpdate\Admin_Settings::get_default_settings
 	 */
 	public function test_should_get_default_api_host() {
-		$actual = self::$instance->get_setting( 'api_host' );
+		$admin_settings = new \AspireUpdate\Admin_Settings();
+		$actual         = $admin_settings->get_setting( 'api_host' );
 
 		$this->assertIsString( $actual, 'The API host value is not a string.' );
-		$this->assertNotEmpty( $actual, 'The API host value is empty. ' . var_export( $actual, true ) );
+		$this->assertNotEmpty( $actual, 'The API host value is empty. ' );
 	}
 }