[Tests] component detection: Add testing scaffolding

Test detection of Class Components and Stateless Function Components
Lay scaffolding for other flavors of tests including further component types, pragma detection, and utils functions

CHANGELOG.md

@@ -7,6 +7,9 @@ This change log adheres to standards from [Keep a CHANGELOG](http://keepachangel
 
 ### Changed
 * [Refactor] [`no-arrow-function-lifecycle`], [`no-unused-class-component-methods`]: use report/messages convention (@ljharb)
+* [Tests] component detection: Add testing scaffolding ([#3149][] @duncanbeevers)
+
+[#3149]: https://github.com/yannickcr/eslint-plugin-react/pull/3149
 
 ## [7.27.1] - 2021.11.18
 

tests/util/Component.js

@@ -0,0 +1,80 @@
+'use strict';
+
+const assert = require('assert');
+const eslint = require('eslint');
+const values = require('object.values');
+
+const Components = require('../../lib/util/Components');
+const parsers = require('../helpers/parsers');
+
+const ruleTester = new eslint.RuleTester({
+  parserOptions: {
+    ecmaVersion: 2018,
+    sourceType: 'module',
+    ecmaFeatures: {
+      jsx: true,
+    },
+  },
+});
+
+describe('Components', () => {
+  describe('static detect', () => {
+    function testComponentsDetect(test, done) {
+      const rule = Components.detect((context, components, util) => ({
+        'Program:exit'() {
+          done(context, components, util);
+        },
+      }));
+
+      const tests = {
+        valid: parsers.all([Object.assign({}, test, {
+          settings: {
+            react: {
+              version: 'detect',
+            },
+          },
+        })]),
+        invalid: [],
+      };
+      ruleTester.run(test.code, rule, tests);
+    }
+
+    it('should detect Stateless Function Component', () => {
+      testComponentsDetect({
+        code: `import React from 'react'
+          function MyStatelessComponent() {
+            return <React.Fragment />;
+          }`,
+      }, (_context, components) => {
+        assert.equal(components.length(), 1, 'MyStatelessComponent should be detected component');
+        values(components.list()).forEach((component) => {
+          assert.equal(
+            component.node.id.name,
+            'MyStatelessComponent',
+            'MyStatelessComponent should be detected component'
+          );
+        });
+      });
+    });
+
+    it('should detect Class Components', () => {
+      testComponentsDetect({
+        code: `import React from 'react'
+        class MyClassComponent extends React.Component {
+          render() {
+            return <React.Fragment />;
+          }
+        }`,
+      }, (_context, components) => {
+        assert(components.length() === 1, 'MyClassComponent should be detected component');
+        values(components.list()).forEach((component) => {
+          assert.equal(
+            component.node.id.name,
+            'MyClassComponent',
+            'MyClassComponent should be detected component'
+          );
+        });
+      });
+    });
+  });
+});