fix(core): ModuleLoader.hasAvailable checks if a given dependency is …

…available

packages/core/spec/io/ModuleLoader.spec.ts

@@ -1,19 +1,20 @@
 import 'mocha';
+
 import path = require('path');
 import { ModuleLoader, Version } from '../../src/io';
 import { expect } from '../expect';
 
 describe('ModuleLoader', () => {
 
-    it('returns the major version number of a given package', () => {
+    it('returns the version number of a given package', () => {
         const loader = new ModuleLoader(__dirname);
 
         const expectedVersion = require('../../package.json').version;
 
         expect(loader.versionOf('../../')).to.equal(new Version(expectedVersion));
     });
 
-    it('returns the major version of the npm-resolved package if the local package could not be found', () => {
+    it('returns the version of the npm-resolved package if the local package could not be found', () => {
         const loader = new ModuleLoader(path.join(__dirname, 'non-existent', 'local', 'directory'));
 
         const expectedVersion = require('tiny-types/package.json').version;                             // tslint:disable-line:no-submodule-imports
@@ -23,6 +24,22 @@ describe('ModuleLoader', () => {
 
     it('complains if neither a local version or the npm-resolved version could not be found', () => {
         const loader = new ModuleLoader(__dirname);
+
         expect(() => loader.versionOf('non-existent-module')).to.throw(Error, `Cannot find module 'non-existent-module/package'`);
     });
+
+    describe('when checking if a given module is available to be required', () => {
+
+        it('returns true if the module is available', () => {
+            const loader = new ModuleLoader(__dirname);
+
+            expect(loader.hasAvailable('tiny-types')).to.equal(true);
+        });
+
+        it('returns false if the module is not available', () => {
+            const loader = new ModuleLoader(__dirname);
+
+            expect(loader.hasAvailable('non-existent-module')).to.equal(false);
+        });
+    });
 });

packages/core/src/io/ModuleLoader.ts

@@ -2,10 +2,28 @@ const Module = require('module');             // tslint:disable-line:no-var-requ
 import * as path from 'path';
 import { Version } from './Version';
 
+/**
+ * @package
+ */
 export class ModuleLoader {
     constructor(public readonly cwd: string) {
     }
 
+    /**
+     * @desc
+     *  Returns true if a given module is available to be required, false otherwise.
+     *
+     * @param {string} moduleId
+     *  NPM module id, for example 'cucumber' or '@serenity-js/core'
+     */
+    hasAvailable(moduleId: string): boolean {
+        try {
+            return !! this.require(moduleId);
+        } catch (e) {
+            return false;
+        }
+    }
+
     /**
      * @package
      *