Properly cleanup server headers during testing (#529)

* Cleanup any HTTP header set as a server variable

* One more adjustment

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## v1.0.3 - 2024-04-15
+
+### Fixed
+
+- Proper unset server headers when testing.
+
 ## v1.0.2 - 2024-04-15
 
 ### Added

src/mantle/testing/class-pending-testable-request.php

@@ -392,6 +392,21 @@ protected function reset_request_state(): void {
 
 		$this->rest_api_response = null;
 
+		// Remove all HTTP_* headers from $_SERVER.
+		foreach ( $_SERVER as $key => $value ) {
+			if ( str_starts_with( $key, 'HTTP_' ) && 'HTTP_HOST' !== $key ) {
+				unset( $_SERVER[ $key ] );
+			}
+
+			if ( isset( $_SERVER['CONTENT_TYPE'] ) ) {
+				unset( $_SERVER['CONTENT_TYPE'] );
+			}
+
+			if ( isset( $_SERVER['REMOTE_ADDR'] ) ) {
+				unset( $_SERVER['REMOTE_ADDR'] );
+			}
+		}
+
 		// phpcs:enable
 	}