# Bank Account

Simulate a bank account supporting opening/closing, withdrawals, and deposits
of money. Watch out for concurrent transactions!

A bank account can be accessed in multiple ways. Clients can make
deposits and withdrawals using the internet, mobile phones, etc. Shops
can charge against the account.

Create an account that can be accessed from multiple threads/processes
(terminology depends on your programming language).

It should be possible to close an account; operations against a closed
account must fail.

## Instructions

Run the test file, and fix each of the errors in turn. When you get the
first test to pass, go to the first pending or skipped test, and make
that pass as well. When all of the tests are passing, feel free to
submit.

Remember that passing code is just the first step. The goal is to work
towards a solution that is as readable and expressive as you can make
it.

Have fun!

## Running tests

In order to run the tests, issue the following command from the exercise
directory:

For running the tests provided, `rebar3` is used as it is the official build and
dependency management tool for erlang now. Please refer to [the tracks installation
instructions](http://exercism.io/languages/erlang/installation) on how to do that.

In order to run the tests, you can issue the following command from the exercise
directory.

```bash
$ rebar3 eunit
```

### Test versioning

Each problem defines a macro `TEST_VERSION` in the test file and
verifies that the solution defines and exports a function `test_version`
returning that same value.

To make tests pass, add the following to your solution:

```erlang
-export([test_version/0]).

test_version() ->
  1.
```

The benefit of this is that reviewers can see against which test version
an iteration was written if, for example, a previously posted solution
does not solve the current problem or passes current tests.

## Questions?

For detailed information about the Erlang track, please refer to the
[help page](http://exercism.io/languages/erlang) on the Exercism site.
This covers the basic information on setting up the development
environment expected by the exercises.


## Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.