This document describes a Coding Dojo, which is a safe place outside of work to practice software development skills through deliberate practice of techniques like test-driven development (TDD) and pair programming. It provides an example assignment to practice an outside-in TDD approach for a bank optical character recognition (OCR) problem that involves parsing account numbers from scanned documents. Participants are instructed to work through the outer application programming interface initially by either ignoring a failing guiding test or stubbing dependencies to make it pass initially before implementing the full solution.

1. Coding Dojo
Salzburg Software Craftmanship
Also on https://www.softwerkskammer.org/groups/salzburg

2. What is a Coding Dojo?
• Safe place outside of work and away from
production code
• Deliberate Practice => Learning
• Relax and Slow down
• You don't have to finish
• Focus on doing it right

3. The Rules
• Test Driven Development
• Pair Programming
• “London” Constraint*
*) London School TDD is Outside-In but Classic TDD can be as well
• Credits to Peter “CodeCop" Kofler
https://www.slideshare.net/pkofler/coding-dojo-bank-ocr-outsidein-2015

4. Outside-In TDD
• build the system from the "outside-in", following the
user interaction through all the parts of the system
• (maybe) create a Guiding Test
• start with top level interactions/collaborators
• create fake dependencies or mock them
• implement using TDD until all tests green
• move "inside" to previously faked collaborator

5. Assignment: Bank OCR
• You work for a bank, which has a machine to assist in reading
letters. The machine scans the paper documents, and produces a
file with a number of entries which each look like this:
• ····_··_·····_··_··_··_··_·
··|·_|·_||_||_·|_···||_||_|
··||_··_|··|·_||_|··||_|·_|
• Each entry is 4 lines long, each line has 27 characters. The first 3
lines contain an account number written using pipes and
underscores, and the fourth line is blank. Each account number
should have 9 digits, all of which should be in the range 1-9.
• Write a program that can take this file and parse it into actual
account numbers

6. Prepare
• Find a pair
• Choose a programming language
• Find samples: https://bitbucket.org/pkofler/
bankocr-kata-setup/ -> src/test/resources
• http://codingdojo.org/kata/BankOCR/
Use Case 1
• Work through outer API

7. Guiding Test
public class GuidingTest {
@Test
public void shouldParseOcrLine() throws IOException {
// TODO failing test, start here
// guiding test from outside in as starting point.
// a) ignore this test
// b) or stub everything in the BankOcr constructor
// c) or let it be red until the end
BankOcr bankOcr = new BankOcr();
List<AccountNumber> accountNumbers = bankOcr.parse(allDigits());
assertEquals(1, accountNumbers.size());
assertEquals(new AccountNumber("123456789"), accountNumbers.get(0));
}
}