feat(gems): installed from the generated Gemfile

README.md

@@ -26,6 +26,14 @@ leverage [rbenv](https://github.com/rbenv/rbenv) to install the version of
 [Ruby](https://www.ruby-lang.org/en/) that is defined in the generated
 `.ruby-version` file.
 
+It is also expected that [bundler](https://bundler.io) is available for
+installing gems from a [Gemfile](https://bundler.io/v2.0/man/gemfile.5.html).
+It can be installed automatically in [rbenv](https://github.com/rbenv/rbenv)
+managed [Ruby](https://www.ruby-lang.org/en/) versions by [including it in your
+`~/.rbenv/default-gems` file](https://github.com/rbenv/rbenv-default-gems#usage)
+when you have the [`rbenv-default-gems` plugin](https://github.com/rbenv/rbenv-default-gems)
+installed.
+
 ## Contributing
 
 <!-- contribution badges -->

src/gems-test.js

@@ -3,6 +3,7 @@ import {assert} from 'chai';
 import sinon from 'sinon';
 import any from '@travi/any';
 import * as fsAsync from '../thirdparty-wrappers/fs';
+import * as execa from '../thirdparty-wrappers/execa';
 import scaffoldGems from './gems';
 
 suite('Gems', () => {
@@ -12,6 +13,7 @@ suite('Gems', () => {
     sandbox = sinon.createSandbox();
 
     sandbox.stub(fsAsync, 'copyFile');
+    sandbox.stub(execa, 'default');
   });
 
   teardown(() => sandbox.restore());
@@ -26,5 +28,7 @@ suite('Gems', () => {
       resolve(__dirname, '..', 'templates', 'Gemfile.rb'),
       `${projectRoot}/Gemfile`
     );
+    assert.calledWith(execa.default, 'bundle', ['install']);
+    assert.isTrue(execa.default.calledAfter(fsAsync.copyFile));
   });
 });

src/gems.js

@@ -1,6 +1,9 @@
 import {resolve} from 'path';
 import {copyFile} from '../thirdparty-wrappers/fs';
+import execa from '../thirdparty-wrappers/execa';
 
 export default async function (projectRoot) {
   await copyFile(resolve(__dirname, '..', 'templates', 'Gemfile.rb'), `${projectRoot}/Gemfile`);
+
+  await execa('bundle', ['install']);
 }

src/ruby-version-test.js

@@ -24,5 +24,6 @@ suite('ruby-version', () => {
 
     assert.calledWith(fsPromises.writeFile, `${projectRoot}/.ruby-version`, '2.6.3');
     assert.calledWith(execa.default, 'rbenv', ['install']);
+    assert.isTrue(execa.default.calledAfter(fsPromises.writeFile));
   });
 });