SWT2 2018/19 - Introductory Exercise

This is an interactive Ruby on Rails 5 exercise, based partly on the "Getting Started with Rails" guide. Interactivity is provided by opening issues in the GitHub issue tracker (through a CI server) that contain instructions on what tasks to tackle next.

We prepared an application stub of an academic paper management system for you that has a failing test case.

Follow these steps to complete the software and the exercise:

1) Set up your repository

• Log-in to Travis CI and enable automatic builds for your exercise repository (add the hpi-swt2-exercise group to the list on the left and flip the switch)

• Ensure that the issue tracker of the repository is active. This can be done in the repository's "Settings" tab.

2) Set up local development environment

• Clone the repository to your local machine

Option 1: Local setup

• Change into the newly created directoy
• Inside the directory, check the used Ruby version using ruby --version. It should be 2.5.0. Other Ruby versions might work, but this is the one that was tested.
• If the correct Ruby version is not used, install a ruby version manager, for example rbenv using the instructions for rbenv installation and ruby-build installation.
  • WARNING: If you already have the Ruby version manager RVM installed, please use that or uninstall it prior to rbenv installation, as the two version managers are incompatible.
• Install Ruby version 2.5.0 with rbenv install 2.5.0 (this might take a few minutes, as Ruby is being compiled)
• The .ruby_version file in the repository instructs the ruby version manager to use the correct version.

Option 2: Use a Virtual Machine

• Install Virtualbox (the VM provider) and Vagrant (to manage VMs) for your platform.
• Run these commands in the root directory of your cloned repository to download and the prepare the VM image:

vagrant up # download the image and start the VM
vagrant ssh # connect via ssh
cd hpi-swt2
mkdir -p "$(rbenv root)"/plugins && git clone https://github.com/rbenv/ruby-build.git "$(rbenv root)"/plugins/ruby-build
rbenv install 2.5.0 #install current ruby
ruby --version # check that 2.5.0 is being used
bundle install # install dependencies
exit # restarting the session for changes to take effect

• To start the development server:

vagrant ssh #connect with VM
cd hpi-swt2
rails s -b 0 #starting rails server, the -b part is necessary since the app is running in a VM and would otherwise drop the requests coming from the host OS

• By default, the application is served on port 3000: http://localhost:3000/
• Edits to files in the local folder will be mirrored into the VM's hpi-swt2 folder as the folders are synced.
• We recommend you open one terminal session that runs the development server and another one to execute commands on the machine (e.g. running tests) or use of a terminal multiplexer. Then you do not have to restart the server after each command.

3) Dive into the code

• Run bundle install to install the dependencies of the project (they are stored in the Gemfile)
• Run rails db:migrate RAILS_ENV=development && rails db:migrate RAILS_ENV=test to migrate the database
• Run rspec to run the tests (RSpec is a test framework for Ruby)
• Try to get the failing test green.

4) Commit and push

• When you are done and the test passes, push your changes.
• Travis CI will now try to build and test your project.

5) Check your inbox / issues

• You will be notified of problems or new exercise work items via GitHub issues on your repository.
• While you wait, see if your code can use some refactorings, continue reading the tutorial, or plan the next steps.

6) For each issue

• Write a new test that documents the missing or failing behavior.
• Commit the failing test and reference the issue.
  • The commit message could be Failing test for #<ISSUE NUMBER>.
  • There is no need to push the failing commit.
• Fix the issue and make your test pass. Then commit the changes.
  • While an issue is open, the exercise will create comments on the issue, notifying you of errors

7) Repeat steps 4 to 6 until the exercise is complete.

Tips:

• The beginning of this exercise is designed to be solved while reading the official Rails tutorial
• Run rspec spec/<path_to_spec>.rb to only run one set of specs
• Have a look at /spec/factories to get inspiration for your data model
• Besides generators and scaffolds, associations and validations are needed
• Occasionally start up the server (rails s) and have a look at the app in your browser
• Look at the Mockup: https://gomockingbird.com/mockingbird/index.html?project=v890g6l#v890g6l/OQMURm (author selection uses a multiple select in this version of the exercise)
• rails db:drop && rails db:migrate deletes the database and recreates it. This might be helpful for error recovery.
• Make sure that all local changes are committed (git status) and pushed to the upstream repository (i.e., the one on GitHub) before the deadline