Add sample tests

.eslintignore

@@ -5,6 +5,11 @@ bin
 build
 dist
 
+# test files
+__tests__
+*.test.js
+*.spec.js
+
 # config files
 *.config.js
 

.eslintrc.js

@@ -15,7 +15,7 @@ module.exports = {
   rules: {
     'linebreak-style': ['error', 'unix'],
     quotes: ['error', 'single'],
-    semi: ['error', 'always'],
+    semi: ['warning', 'always'],
     'import/no-commonjs': 'error'
   }
 };

babel.config.js

-module.exports = {
-  presets: ['@babel/preset-env'],
-  ignore: ['**/__tests__/**', '*.test.js', '*.spec.js']
+module.exports = api => {
+  const isTest = api.env('test');
+
+  api.cache(true);
+  // configs to load when testing environment
+  if (isTest)
+    return {
+      presets: ['@babel/preset-env']
+    };
+
+  return {
+    presets: ['@babel/preset-env'],
+    ignore: ['**/__tests__/**', '*.test.js', '*.spec.js']
+  };
 };

jest.config.js

+module.exports = {};

src/__tests__/index.test.js

+describe('sample test', () => {
+  it('jest works', () => {
+    expect(true).toBe(true);
+  });
+});