Add test for missing composer json file

.gitignore

@@ -28,7 +28,7 @@ build
 ############
 
 node_modules/
-vendor/
+/vendor/
 
 ############
 ## OSes

includes/Checker/Checks/Plugin_Repo/File_Type_Check.php

@@ -400,7 +400,7 @@ protected function look_for_composer_files( Check_Result $result, array $files )
 				$result,
 				sprintf(
 					/* translators: 1: directory, 2: filename */
-					esc_html__( 'The "%1$s" directory exists, but "%2$s" is missing.', 'plugin-check' ),
+					esc_html__( 'The "%1$s" directory using composer exists, but "%2$s" file is missing.', 'plugin-check' ),
 					'/vendor',
 					'composer.json'
 				),

tests/phpunit/testdata/plugins/test-plugin-file-type-composer-errors/load.php

@@ -0,0 +1,17 @@
+<?php
+/**
+ * Plugin Name: Test Plugin File Type Composer Files
+ * Plugin URI: https://github.com/WordPress/plugin-check
+ * Description: Some plugin description.
+ * Author: WordPress Performance Team
+ * Author URI: https://make.wordpress.org/plugins/
+ * License: GPLv2 or later
+ * License URI: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+ * Text Domain: test-plugin-file-type-composer-errors
+ *
+ * @package test-plugin-file-type-composer-errors
+ */
+
+/**
+ * Plugin folder contains a vendor folder without composer.json file.
+ */

tests/phpunit/testdata/plugins/test-plugin-file-type-composer-errors/vendor/autoload.php

@@ -0,0 +1,3 @@
+<?php
+
+// autoload.php @generated by Composer

tests/phpunit/tests/Checker/Checks/File_Type_Check_Tests.php

@@ -150,4 +150,18 @@ public function test_run_with_library_core_errors() {
 		$this->assertArrayHasKey( 0, $errors['jquery.js'][0] );
 		$this->assertCount( 1, wp_list_filter( $errors['jquery.js'][0][0], array( 'code' => 'library_core_files' ) ) );
 	}
+
+	public function test_run_with_composer_errors() {
+		$check_context = new Check_Context( UNIT_TESTS_PLUGIN_DIR . 'test-plugin-file-type-composer-errors/load.php' );
+		$check_result  = new Check_Result( $check_context );
+
+		$check = new File_Type_Check( File_Type_Check::TYPE_COMPOSER );
+		$check->run( $check_result );
+
+		$warnings = $check_result->get_warnings();
+
+		$this->assertNotEmpty( $warnings );
+
+		$this->assertCount( 1, wp_list_filter( $warnings['composer.json'][0][0], array( 'code' => 'missing_composer_json_file' ) ) );
+	}
 }