Introducing BDD to Legacy Applications with SpecFlow/Cucumber (Agilia Conference 2016)

Gáspár Nagy
coach • trainer • bdd addict • creator of specflow
@gasparnagy • gaspar@specsolutions.eu
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 +
Automation
on 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

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?

The first change request

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

Red

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!

5. Pick off a bite!
1
2
3
4
5
8
9
#6
7
Aut
#
#’

5. Pick off a bite
Refactor

We have scaffolded our application
for implementing this feature!

6. Describe the new feature
Red

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…

• 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 Nagy
coach • trainer • bdd addict • creator of specflow
@gasparnagy • gaspar@specsolutions.eu
Thank you!

Introducing BDD to Legacy Applications with SpecFlow/Cucumber (Agilia Conference 2016)

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