Source

File: wp-admin/includes/class-wp-site-health.php

public function get_test_is_in_debug_mode() {
		$result = array(
			'label'       => __( 'Your site is not set to output debug information' ),
			'status'      => 'good',
			'badge'       => array(
				'label' => __( 'Security' ),
				'color' => 'blue',
			),
			'description' => sprintf(
				'<p>%s</p>',
				__( 'Debug mode is often enabled to gather more details about an error or site failure, but may contain sensitive information which should not be available on a publicly available website.' )
			),
			'actions'     => sprintf(
				'<p><a href="%s" target="_blank" rel="noopener noreferrer">%s <span class="screen-reader-text">%s</span><span aria-hidden="true" class="dashicons dashicons-external"></span></a></p>',
				/* translators: Documentation explaining debugging in WordPress. */
				esc_url( __( 'https://wordpress.org/support/article/debugging-in-wordpress/' ) ),
				__( 'Learn more about debugging in WordPress.' ),
				/* translators: Accessibility text. */
				__( '(opens in a new tab)' )
			),
			'test'        => 'is_in_debug_mode',
		);

		if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
			if ( defined( 'WP_DEBUG_LOG' ) && WP_DEBUG_LOG ) {
				$result['label'] = __( 'Your site is set to log errors to a potentially public file.' );

				$result['status'] = ( 0 === strpos( ini_get( 'error_log' ), ABSPATH ) ) ? 'critical' : 'recommended';

				$result['description'] .= sprintf(
					'<p>%s</p>',
					sprintf(
						/* translators: %s: WP_DEBUG_LOG */
						__( 'The value, %s, has been added to this website&#8217;s configuration file. This means any errors on the site will be written to a file which is potentially available to all users.' ),
						'<code>WP_DEBUG_LOG</code>'
					)
				);
			}

			if ( defined( 'WP_DEBUG_DISPLAY' ) && WP_DEBUG_DISPLAY ) {
				$result['label'] = __( 'Your site is set to display errors to site visitors' );

				$result['status'] = 'critical';

				$result['description'] .= sprintf(
					'<p>%s</p>',
					sprintf(
						/* translators: 1: WP_DEBUG_DISPLAY, 2: WP_DEBUG */
						__( 'The value, %1$s, has either been enabled by %2$s or added to your configuration file. This will make errors display on the front end of your site.' ),
						'<code>WP_DEBUG_DISPLAY</code>',
						'<code>WP_DEBUG</code>'
					)
				);
			}
		}

		return $result;
	}