Refactor tests by moving render function into helpers

`render` is an alias for `ReactDOMServer.renderToStaticMarkup`

Update `render` function to check that the first argument is a
valid React element; otherwise, throw an error.

Author: remarkablemark

test/dom-to-react.js

@@ -5,9 +5,9 @@
  */
 var assert = require('assert');
 var React = require('react');
-var ReactDOMServer = require('react-dom/server');
 var htmlToDOMServer = require('../lib/html-to-dom-server');
 var domToReact = require('../lib/dom-to-react');
+var helpers = require('./helpers/');
 var data = require('./data');
 
 /**
@@ -78,9 +78,7 @@ describe('dom-to-react parser', function() {
         var html = data.html.void;
         var reactElements = domToReact(htmlToDOMServer(html));
         assert.doesNotThrow(function() {
-            ReactDOMServer.renderToStaticMarkup(
-                React.createElement('div', {}, reactElements)
-            );
+            helpers.render(React.createElement('div', {}, reactElements));
         });
     });
 

test/helpers/index.js

@@ -5,6 +5,21 @@
  */
 var assert = require('assert');
 var util = require('util');
+var React = require('react');
+var ReactDOMServer = require('react-dom/server');
+
+/**
+ * Render a React element to static HTML markup.
+ *
+ * @param  {ReactElement} reactElement - The React element.
+ * @return {String}                    - The static HTML markup.
+ */
+function render(reactElement) {
+    if (!React.isValidElement(reactElement)) {
+        throw new Error(reactElement, 'is not a valid React element.');
+    }
+    return ReactDOMServer.renderToStaticMarkup(reactElement);
+}
 
 /**
  * Test for deep equality between objects that have circular references.
@@ -65,5 +80,6 @@ function deepEqualCircular(actual, expected) {
  * Export assert helpers.
  */
 module.exports = {
-    deepEqualCircular: deepEqualCircular
+    deepEqualCircular: deepEqualCircular,
+    render: render
 };

test/html-to-react.js

@@ -5,20 +5,10 @@
  */
 var assert = require('assert');
 var React = require('react');
-var ReactDOMServer = require('react-dom/server');
 var Parser = require('../');
+var helpers = require('./helpers/');
 var data = require('./data');
 
-/**
- * Render a React element to static HTML markup.
- *
- * @param  {ReactElement} reactElement - The React element.
- * @return {String}                    - The static HTML markup.
- */
-function render(reactElement) {
-    return ReactDOMServer.renderToStaticMarkup(reactElement);
-}
-
 /**
  * Tests for `htmlToReact`.
  */
@@ -44,35 +34,35 @@ describe('html-to-react', function() {
         it('converts single HTML element to React', function() {
             var html = data.html.single;
             var reactElement = Parser(html);
-            assert.equal(render(reactElement), html);
+            assert.equal(helpers.render(reactElement), html);
         });
 
         it('converts single HTML element and ignores comment', function() {
             var html = data.html.single;
             // comment should be ignored
             var reactElement = Parser(html + data.html.comment);
-            assert.equal(render(reactElement), html);
+            assert.equal(helpers.render(reactElement), html);
         });
 
         it('converts multiple HTML elements to React', function() {
             var html = data.html.multiple;
             var reactElements = Parser(html);
             assert.equal(
-                render(React.createElement('div', {}, reactElements)),
+                helpers.render(React.createElement('div', {}, reactElements)),
                 '<div>' + html + '</div>'
             );
         });
 
         it('converts complex HTML to React', function() {
             var html = data.html.complex;
             var reactElement = Parser(html);
-            assert.equal(render(reactElement), html);
+            assert.equal(helpers.render(reactElement), html);
         });
 
         it('converts SVG to React', function() {
             var svg = data.svg.complex;
             var reactElement = Parser(svg);
-            assert.equal(render(reactElement), svg);
+            assert.equal(helpers.render(reactElement), svg);
         });
 
     });
@@ -94,7 +84,7 @@ describe('html-to-react', function() {
                     }
                 });
                 assert.equal(
-                    render(reactElement),
+                    helpers.render(reactElement),
                     html.replace('<title>Title</title>', '<meta charset="utf-8"/>')
                 );
             });
@@ -112,7 +102,7 @@ describe('html-to-react', function() {
                     }
                 });
                 assert.notEqual(
-                    render(reactElement),
+                    helpers.render(reactElement),
                     html.replace(
                         '<header id="header">Header</header>',
                         '<h1>Heading</h1>'