introducing bdd to legacy...

Gáspár Nagycoach • trainer • bdd addict • creator of specflow

@gasparnagy • [email protected]

Introducing BDD to Legacy Applications

with SpecFlow/Cucumber

Agilia Conference 2016 • 6/4/2016

Copyright © Gaspar Nagy

bdd addict

given.when.then

CAUTION!

bddaddict.com

on the stage


What is BDD?


BDD =

Product Ownership +

Collaboration +

Automationon the product

of requirements

real


Smart Calculator

Demo: BDD Drives Development


How can I apply this to legacy apps?


Working with a legacy app is like renovating a house…

Renovation can be challenging…

Source: http://kadarkocka.blogspot.com/2011_08_01_archive.html


My Story

The project was delivered in cooperation with TechTalk (www.techtalk.at)

It was modern…

Source: http://irodahaz.info

Complex domain…

106 failing (integration?) tests


… and other challenges

• 17 GB test database

• 46 projects

• 300k lines of code

• >2 minutes build time


What can I do with this?

Source: Wikipedia


The first change request

Deployment –

Workflow


0. Get the infrastructure ready

We need a healthy local dev and CI environment!

• Make a dummy test and get it running!

• Ignore/skip/delete unstable

tests

• Setup the desired testing

model (e.g. SpecFlow)

• Test core dependencies

(e.g. “When I do

something with the

database”)


1. Capture current behavior

• Based on the way it was demoed to you

• Do not worry about automation

• Do not worry about details

• Do not worry about exact phrasing


TDD Cycle


ATDD Cycle


1. Capture current behaviorRed


2. Automate “Then” steps

• Feel free to hard-wire concrete data (IDs)!

Red


3. Improve errors

Our scenario fails. Is it easy to understand why?

• Check the test output and improve if necessary!

Red


4. Automate “When” with hard-wired data

• We have something to start with!

• (But its obviously nasty with “2347599”)

Green


We need to get rid of the hard-wired data!

1

2

3

4

5

8

9

#6

7

5. Pick off a bite!

1

2

3

4

5

8

9

#6

7

Aut

#

#’


5. Pick off a biteRefactor


We have scaffolded our application for implementing this feature!


6. Describe the new featureRed


7. Automate and implement it

• You can even forget that your are maintaining a legacy app here…

Green


8. Discover corner cases

• We have seen a “happy path” so far…

• But what happens if…• …there are associated deliverables

• …the package is partially frozen

• …


9. Pick low hanging fruits

• We have developed an automation interface for a part of the application

• Can we use it to cover other usual cases?


Summary: The first change request

• We addressed the system through a new feature

• Ensured that the test infrastructure works

• Scaffolded the app with a test for the current behavior using hard wired data

• Refactored the automation to eliminate some parts of these data – taken apart a bit of the scaffolding

• Described and implemented the new feature

• Used the automation infrastructure for further tests


The first bug


This is a nasty bug…

• Because• Workflow is handled by WF 3

• Script is executed on a remote machine through SSH

• A very old dead OSS project is used for SSH (no timeout setting)

• I cannot even try this out!


Ok… calm down.

We have a process…


1. Capture current behavior

• Do not worry about automation

• Do not worry about details

• Do not worry about exact phrasing

Red


2. How to test SSH?

A focused scenario can drive you to find a solution for automation

• Find a tool that can be well automated and can be used for SSH – Vagrant?

• Set it up locally (don’t worry about the automation yet)

• Make the test pass with the local setup• Do you remember deployment #2347599?

• Refactor: Eliminate hard-wired details

Green


3. Describe bug as a scenario

Red


4. Fix the bug!

• With the test we could find the bug that was actually in the SSH library

Green


Shall we keep regression tests?

• It depends…

• If the bug highlighted an important business case –keep it!

• If it described a special situation (and the bugfix was covered by unit/integration tests) – delete it!

• Maintaining regression tests is very costly!


Summary: The first bug

• Similarly to new features, addressing the bugs by capturing the current behavior as scenarios is helpful

• Don’t be afraid of deleting the regression test after fixing the bug if it does not represent an important business case


Working on a legacy app does not mean that you cannot apply BDD

process.

The scenarios can guide you to discover more and more from the

application!


Happy maintenance!

Gáspár Nagycoach • trainer • bdd addict • creator of specflow

@gasparnagy • [email protected]

Thank you!

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