Add module loader initial tests

also add LLMS_Module_Loader::$instance->is_module_loaded($name) as a way to
check if a module has been loaded.

includes/modules/class-llms-module-loader.php

@@ -115,13 +115,8 @@ private function load() {
 
 		foreach ( $to_load as $module ) {
 
-			// define the constant as true if it hasn't been defined explicitly.
-			if ( ! defined( $module['constant_name'] ) ) {
-				define( $module['constant_name'], true );
-			}
-
-			// bail, if the constant's value is explcitly defined to false.
-			if ( constant( $module['constant_name'] ) === false ) {
+			// bail, if the constant's value is explicitly defined to false.
+			if ( defined( $module['constant_name'] ) && constant( $module['constant_name'] ) === false ) {
 				continue;
 			}
 
@@ -162,6 +157,30 @@ private function load() {
 
 	}
 
+	/**
+	 * Checks whether a module has been loaded.
+	 *
+	 * @since [version]
+	 *
+	 * @param string $name Module name.
+	 * @return bool Whether or not the given module has been loaded.
+	 */
+	public function is_module_loaded( $name ) {
+
+		$loaded = in_array( $name, wp_list_pluck( $this->loaded, 'name' ), true );
+
+		/**
+		 * Filters whether or not a module has been loaded.
+		 *
+		 * @since [version]
+		 *
+		 * @param bool               $loaded  Whether or not the given module has been loaded.
+		 * @param LLMS_Module_Loader $request This LLMS_Module_Loader instance.
+		 */
+		return apply_filters( 'llms_is_module_loaded', $loaded, $this );
+
+	}
+
 	/**
 	 * Loads Module Information.
 	 *

tests/unit-tests/modules/class-llms-test-module-loader.php

@@ -0,0 +1,66 @@
+<?php
+/**
+ * Tests for LifterLMS Module loader
+ *
+ * @group modules
+ *
+ * @since [version]
+ * @version [version]
+ */
+class LLMS_Test_Module_Loader extends LLMS_UnitTestCase {
+
+	/**
+	 * Test the modules loading.
+	 *
+	 * @since [version]
+	 *
+	 * @return void
+	 */
+	public function test_load() {
+
+		// get modules to be loades.
+		$modules = $this->_get_load_info();
+
+		// check they've been loaded.
+		foreach ( $modules as &$module ) {
+			$module['actions'] = did_action( "lifterlms_module_{$module['name']}_loaded" );
+			$this->assertEquals( 1, $module['actions'] );
+			LLMS_Module_Loader::instance()->is_module_loaded( $module['name'] );
+		}
+
+		// define module constants to false so to skip the loading.
+		foreach ( $modules as $module ) {
+			! defined( $module['constant_name'] ) && define( $module['constant_name'], FALSE );
+		}
+
+		// Fire the loading once again.
+		$loaded = LLMS_Unit_Test_Util::call_method( LLMS_Module_Loader::instance(), 'load' );
+
+		// check they've not been loaded this time.
+		$this->assertEquals( array(), $loaded );
+
+		foreach ( $modules as &$module ) {
+			$actions_counter   = $module['actions'];
+			$module['actions'] = did_action( "lifterlms_module_{$module['name']}_loaded" );
+			$this->assertEquals( $actions_counter, $module['actions'] );
+		}
+
+	}
+
+	/**
+	 * Get the array of modules to load.
+	 * Of the type:
+	 *    $module = array(
+	 *        'name' => 'module-name',
+	 *        'file_path' => 'lifterlms/includes/modules/module-name/class-llms-module-name.php',
+	 *        'constant_name' => 'LLMS_MODULE_NAME',
+	 *    );
+	 *
+	 * @since [version]
+	 *
+	 * @return array
+	 */
+	private function _get_load_info() {
+		return LLMS_Unit_Test_Util::call_method( LLMS_Module_Loader::instance(), 'load_info' );
+	}
+}