diff --git a/example/arkham.js b/example/arkham.js
new file mode 100644
index 0000000..e69de29
diff --git a/example/arkham/index.js b/example/arkham/index.js
new file mode 100644
index 0000000..e69de29
diff --git a/example/batcave.ts b/example/batcave.ts
new file mode 100644
index 0000000..e69de29
diff --git a/example/batcave/index.ts b/example/batcave/index.ts
new file mode 100644
index 0000000..e69de29
diff --git a/index.js b/index.js
index b17b28d..b355aa5 100644
--- a/index.js
+++ b/index.js
@@ -1,5 +1,5 @@
 const { existsSync, lstatSync } = require('fs');
-const { dirname, resolve } = require('path');
+const { join, dirname, resolve, posix, extname, basename } = require('path');
 
 module.exports = {
     configs: {
@@ -13,7 +13,9 @@ module.exports = {
     },
     rules: {
         'require-extensions': rule((context, node, path) => {
-            if (!existsSync(path)) {
+            const fileExt = extname(context.getFilename());
+
+            if (!existsSync(path) || existsSync(`${path}${fileExt}`)) {
                 let fix;
                 if (!node.source.value.includes('?')) {
                     fix = (fixer) => {
@@ -29,12 +31,18 @@ module.exports = {
             }
         }),
         'require-index': rule((context, node, path) => {
-            if (existsSync(path) && lstatSync(path).isDirectory()) {
+            const fileExt = extname(context.getFilename());
+            const conflictingFile = join(dirname(path), `${basename(path)}${fileExt}`);
+
+            if (existsSync(path) && lstatSync(path).isDirectory() && !existsSync(conflictingFile)) {
                 context.report({
                     node,
                     message: 'Directory paths must end with index.js',
                     fix(fixer) {
-                        return fixer.replaceText(node.source, `'${node.source.value}/index.js'`);
+                        const { value: source } = node.source;
+
+                        const prefix = source.startsWith('./') || source === '.' ? './' : '';
+                        return fixer.replaceText(node.source, `'${prefix}${posix.join(source, 'index.js')}'`);
                     },
                 });
             }
@@ -52,7 +60,9 @@ function rule(check) {
                 const source = node.source;
                 if (!source) return;
                 const value = source.value.replace(/\?.*$/, '');
-                if (!value || !value.startsWith('.') || value.endsWith('.js')) return;
+
+                const validExtensions = ['.js', '.jsx', '.cjs', '.mjs'];
+                if (!value || !value.startsWith('.') || validExtensions.some(ext => value.endsWith(ext))) return;
 
                 check(context, node, resolve(dirname(context.getFilename()), value));
             }
diff --git a/package-lock.json b/package-lock.json
index eb621e3..8f28da3 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
     "name": "eslint-plugin-require-extensions",
-    "version": "0.1.2",
+    "version": "0.1.3",
     "lockfileVersion": 2,
     "requires": true,
     "packages": {
         "": {
             "name": "eslint-plugin-require-extensions",
-            "version": "0.1.2",
+            "version": "0.1.3",
             "license": "Apache-2.0",
             "devDependencies": {
                 "eslint": "^8.23.0",
diff --git a/package.json b/package.json
index 20876a5..91b8ee2 100644
--- a/package.json
+++ b/package.json
@@ -5,9 +5,6 @@
     "repository": "https://github.com/solana-labs/eslint-plugin-require-extensions",
     "license": "Apache-2.0",
     "type": "commonjs",
-    "scripts": {
-        "test": "eslint . --report-unused-disable-directives"
-    },
     "engines": {
         "node": ">=16"
     },
@@ -22,7 +19,7 @@
     ],
     "scripts": {
         "fmt": "prettier --write '{*,**/*}.{ts,tsx,js,jsx,json}'",
-        "test": "eslint . --report-unused-disable-directives"
+        "test": "node --test && eslint . --report-unused-disable-directives"
     },
     "publishConfig": {
         "access": "public"
diff --git a/tests/index.test.js b/tests/index.test.js
new file mode 100644
index 0000000..759763b
--- /dev/null
+++ b/tests/index.test.js
@@ -0,0 +1,150 @@
+const { describe, it } = require('node:test');
+const path = require('node:path');
+const { RuleTester } = require('eslint');
+const { rules } = require('../index');
+
+const ruleTester = new RuleTester({ parserOptions: { ecmaVersion: 2020, sourceType: 'module' } });
+const filename = path.join(path.dirname(__dirname), 'example/index.js');
+
+global.describe = describe;
+global.it = it;
+
+describe('eslint-plugin-require-extensions', () => {
+    ruleTester.run('require-extensions', rules['require-extensions'], {
+        valid: [
+            {
+                name: 'import with extension',
+                code: "import test from './dir/index.js'",
+                filename,
+            },
+            {
+                name: 'package import',
+                code: "import batcave from '@wayne/foundation'",
+                filename,
+            },
+            {
+                name: 'import jsx',
+                code: "import test from './joker.jsx'",
+                filename,
+            },
+            {
+                name: 'import cjs',
+                code: "import test from './joker.cjs'",
+                filename,
+            },
+            {
+                name: 'import mjs',
+                code: "import test from './joker.mjs'",
+                filename,
+            },
+        ],
+        invalid: [
+            {
+                name: 'import without extension',
+                code: "import test from './dir/index'",
+                output: "import test from './dir/index.js'",
+                errors: ['Relative imports and exports must end with .js'],
+                filename,
+            },
+            {
+                name: 'file with sibling folder of same name',
+                code: "import arkham from './arkham'",
+                output: "import arkham from './arkham.js'",
+                errors: ['Relative imports and exports must end with .js'],
+                filename,
+            },
+            {
+                name: 'typescript file with sibling folder of same name',
+                code: "import batcave from './batcave'",
+                output: "import batcave from './batcave.js'",
+                errors: ['Relative imports and exports must end with .js'],
+                filename: path.join(path.dirname(__dirname), 'example/index.ts'),
+            },
+        ],
+    });
+
+    ruleTester.run('require-index', rules['require-index'], {
+        valid: [
+            {
+                name: 'import from index.js',
+                code: "import test from './dir/index.js'",
+                filename,
+            },
+            {
+                name: 'package import',
+                code: "import batcave from '@wayne/foundation'",
+                filename,
+            },
+            {
+                name: 'bail on import from file with sibling folder of same name',
+                code: "import arkham from './arkham'",
+                filename,
+            },
+        ],
+        invalid: [
+            {
+                name: 'import without index',
+                code: "import './dir'",
+                output: "import './dir/index.js'",
+                errors: ['Directory paths must end with index.js'],
+                filename,
+            },
+            {
+                name: 'export * without index',
+                code: "export * from './dir'",
+                output: "export * from './dir/index.js'",
+                errors: ['Directory paths must end with index.js'],
+                filename,
+            },
+            {
+                name: 'export named without index',
+                code: "export { joker } from './dir'",
+                output: "export { joker } from './dir/index.js'",
+                errors: ['Directory paths must end with index.js'],
+                filename,
+            },
+            {
+                name: "import from '../'",
+                code: "import plugin from '../'",
+                output: "import plugin from '../index.js'",
+                errors: ['Directory paths must end with index.js'],
+                filename,
+            },
+            {
+                name: "import from '..'",
+                code: "import plugin from '..'",
+                output: "import plugin from '../index.js'",
+                errors: ['Directory paths must end with index.js'],
+                filename,
+            },
+            {
+                name: "import from './'",
+                code: "import index from './'",
+                output: "import index from './index.js'",
+                errors: ['Directory paths must end with index.js'],
+                filename: path.join(path.dirname(__dirname), 'example/other.js'),
+            },
+            {
+                name: "import from '.'",
+                code: "import index from '.'",
+                output: "import index from './index.js'",
+                errors: ['Directory paths must end with index.js'],
+                filename: path.join(path.dirname(__dirname), 'example/other.js'),
+            },
+            {
+                name: 'named import without index',
+                code: "import { batmobile } from './dir'",
+                output: "import { batmobile } from './dir/index.js'",
+                errors: ['Directory paths must end with index.js'],
+                filename,
+            },
+            {
+                name: 'default import without index',
+                code: "import batmobile from './dir'",
+                output: "import batmobile from './dir/index.js'",
+                errors: ['Directory paths must end with index.js'],
+                filename,
+            },
+        ],
+    });
+});