ATM Controller Sample

An implementation of a simple ATM controller with its test codes, as a custom task sample project.

1. Instructions

• You can clone project from this GitHub repository as you wish.
• Project language is Python 3+
• 'atm_controller.py' has all of the features requested, but have no specific entry point.
  • 'driver.py' has an entry point like a driver class, and this is a presumed way to start the integrated system.
  • Currently, only test codes are prepared, and driver class/module is not working.
• 'test/test_atm_controller.py' is a test code based on Python 'unittest' module. You can run a test with this file.(also has entry point)

2. Documentary

2.1 Requirements & Prerequisites

• There are four stages given, and corresponding actions are required for each stage.

  Insert Card => PIN number => Select Account => See Balance/Deposit/Withdraw

• Only dollars are counted; data type for money/balance will be an integer type.
• It is unnecessary to implement or to try integration with real ATM machine(hardware) and core banking system parts; but keep in mind that the jobs would be done in the future.
• There's a 'bank API' provided to examine that the PIN number is correct.
• It is allowed to simplify some complex problems, and the development of core structure of ATM software and corresponding tests are main goal of this project.

2.2 Insights & Approaches

• First of all, requirements seemed to be simple. The work flow is quite straight forward, so it would be easy to describe it into finite states.
• The controller has a 'Session', which is a kind of lifecycle for each use case.
• Concerning single thread program. The controller basically has the context(main-thread), and call hardware input if necessary.(blocking operation)
• For integrity of the controller, both 'bank API' and 'hardware driver' are referenced by the controller, not vice versa.
  • This may disable both hardware and software interruptions in real world situations; but let's keep it simple.

2.3 Troubles & Concerns

• How can I get accounts when PIN number is correct? -> Assuming that there's an another bank API that I can retrieve those accounts.
• It would be better with async control in real example, but for simplification and easy testing, the technique is renounced.