Add a test to ensure to fix #249

Author: rhysd

tests/lib/rules/forbid-prop-types.js

@@ -132,6 +132,21 @@ ruleTester.run('forbid-prop-types', rule, {
       classes: true,
       jsx: true
     }
+  }, {
+    code: [
+      'class First extends React.Component {',
+      '  render() {',
+      '    return <div />;',
+      '  }',
+      '}',
+      'First.propTypes = {',
+      '  elem: PropTypes.instanceOf(HTMLElement)',
+      '};'
+    ].join('\n'),
+    ecmaFeatures: {
+      classes: true,
+      jsx: true
+    }
   }, {
     code: [
       'class Hello extends React.Component {',