implemented validation

Author: mightyaleksey

lib/validate.js

@@ -1,3 +1,7 @@
+const difference = require('lodash').difference;
+const forEach = require('lodash').forEach;
+const keys = require('lodash').keys;
+
 const rules = {
   // hook
   extensions:         'array|string',
@@ -14,4 +18,25 @@ const rules = {
   rootDir:            'string',
 };
 
-module.exports = function validate(options) {}
+const tests = {
+  array:    require('lodash').isArray,
+  function: require('lodash').isFunction,
+  string:   require('lodash').isString,
+};
+
+module.exports = function validate(options) {
+  const unknownOptions = difference(keys(options), keys(rules));
+  if (unknownOptions.length) {
+    throw new Error(`unknown arguments: ${unknownOptions.join(', ')}.`);
+  }
+
+  forEach(rules, (types, rule) => {
+    if (typeof options[rule] === 'undefined') {
+      return;
+    }
+
+    if (!types.split('|').some(type => tests[type](options[rule]))) {
+      throw new TypeError(`should specify ${types} as ${rule}`);
+    }
+  });
+}

test/lib/validate.js

@@ -0,0 +1,19 @@
+const validate = require('../../lib/validate');
+
+suite('lib/validate', () => {
+  test('should thrown an error for the option with multiple types if wrong type specified', () => {
+    assert.throws(() => validate({extensions: null}, TypeError));
+  });
+
+  test('should thrown an error for the option with single type if wrong type specified', () => {
+    assert.throws(() => validate({preprocessCss: ''}, TypeError));
+  });
+
+  test('should NOT throw an error for the valid type', () => {
+    assert.doesNotThrow(() => validate({preprocessCss: function () {}}));
+  });
+
+  test('should throw an error if unknown options are specified', () => {
+    assert.throws(() => validate({a: '', b: ''}), Error);
+  });
+});