Add test for loadNpmTasks

package.json

@@ -58,7 +58,8 @@
     "grunt-jscs": "~2.3.0",
     "semver": "2.1.0",
     "shelljs": "~0.5.3",
-    "temporary": "~0.0.4"
+    "temporary": "~0.0.4",
+    "through2": "~2.0.0"
   },
   "files": [
     "lib"

test/fixtures/load-npm-tasks/package.json

@@ -0,0 +1,7 @@
+{
+  "private": true,
+  "name": "load-npm-tasks",
+  "devDependencies": {
+    "grunt-foo-plugin": "1.0.0"
+  }
+}

test/gruntfile/load-npm-tasks.js

@@ -0,0 +1,51 @@
+/*
+ * grunt
+ * http://gruntjs.com/
+ *
+ * Copyright (c) 2016 "Cowboy" Ben Alman
+ * Licensed under the MIT license.
+ * https://github.com/gruntjs/grunt/blob/master/LICENSE-MIT
+ */
+
+'use strict';
+
+var Log = require('grunt-legacy-log').Log;
+var assert = require('assert');
+var through = require('through2');
+
+module.exports = function(grunt) {
+  grunt.file.setBase('../fixtures/load-npm-tasks');
+
+  // Create a custom log to assert output
+  var stdout = [];
+  var oldlog = grunt.log;
+  var stream = through(function(data, enc, next) {
+    stdout.push(data.toString());
+    next(null, data);
+  });
+  stream.pipe(process.stdout);
+  var log = new Log({
+    grunt: grunt,
+    outStream: stream,
+  });
+  grunt.log = log;
+
+  // Load a npm task
+  grunt.loadNpmTasks('grunt-foo-plugin');
+
+  // Run them
+  grunt.registerTask('default', ['foo', 'done']);
+
+  // Assert they loaded and ran correctly
+  grunt.registerTask('done', function() {
+    grunt.log = oldlog;
+    stdout = stdout.join('\n');
+    try {
+      assert.ok(stdout.indexOf('foo has ran.') !== -1, 'oh-four task should have ran.');
+    } catch (err) {
+      grunt.log.subhead(err.message);
+      grunt.log.error('Expected ' + err.expected + ' but actually: ' + err.actual);
+      throw err;
+    }
+  });
+};