Do you remember your childhood when your mom or an older story teller pronounced the most interesting words in the world? “Once upon a time…” Let me be now your story teller, listen to my story about a legacy app, a painful problem, the search for the solution and the lucky outcome. No, no, this is not the story about a new green field project where everything is so clear. However, even in this story there is a master builder, who shows the developers how to scaffold the legacy app with BDD scenarios using SpecFlow or Cucumber and everything will be all right in the end. Let me tell you about different strategies, collaboration and testing patterns that can be followed in such a renovation-like situation. So, are you ready?... “Once upon a time there was a company where…” To be continued at my session

1. Scaffolding a legacy
app with BDD
scenarios
using SpecFlow/Cucumber
HUSTEF 2016, Budapest
24/10/2016
Gáspár Nagy
coach • trainer • bdd addict • creator of specflow
@gasparnagy • gaspar@specsolutions.eu

2. Copyright © Gaspar Nagy
bdd addict
given.when.then
CAUTION!
bddaddict.com
on the stage

3. Copyright © Gaspar Nagy
What is BDD?

4. Copyright © Gaspar Nagy
[HttpPost]
public ActionResult Answer(int answer)
{
TriviaEntities db = new TriviaEntities();
var question = db.FindQuestion(CurrentQuestion);
if (question.Type == QuestionType.Easy)
{
db.AddScore(question, user, 10);
}
else
{
db.AddScore(question, user, 50);
}
var model = new GameModel
{ Score = db.GetScore(question, user) };
return View(model);
}
implement
feedback
Classic model

5. Copyright © Gaspar Nagy
Scenario: Correct easy answer scores 10
Given I register a team
When I submit a correct easy answer
Then my score should be 10
Collaboration
Automation with
Cucumber/SpecFlow
BDD Process

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Test Driven Development
Failing test Make it pass
Make it clean

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TDD Cycle
Red Green
Refactor

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How can I apply this to
legacy apps?

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Working with a legacy app is like
renovating a house…

10. Renovation can be challenging…
Source: http://kadarkocka.blogspot.com/2011_08_01_archive.html

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

12. It was modern…
Source: http://irodahaz.info

13. Complex domain…

14. 106 failing (integration?) tests

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… and other challenges
• 17 GB test database
• 46 projects
• 300k lines of code
• >2 minutes build time

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What can I do with this?

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18. Source: Wikipedia

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The first change request

20. Deployment –
Workflow

21. Change request
Source: http://irodahaz.info
We need to replace
that window up
there!

22. Copyright © Gaspar Nagy
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”)

23. Get the infrastructure ready
Source: http://hfsaustralia.com.au/storage.html

24. Copyright © Gaspar Nagy
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

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TDD Cycle
Red Green
Refactor

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1. Capture current behavior
Red

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2. Automate “Then” steps
• Feel free to hard-wire concrete data (IDs)!
Red

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3. Automate “When”
with hard-wired data
• We have something to start with!
• (But its obviously nasty with “2347599”)
Green

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30. We’ve got a scaffolding!
Source: Wikipedia

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

32. 1
2
3
4
5
8
9
#6
7

33. Remove a bit of scaffolding

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

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4. Pick off a bite
Refactor

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We have scaffolded our application for
implementing this feature!

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5. Describe the new feature
Red

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6. Automate and implement
it
• You can even forget that your are maintaining a legacy app
here…
Green

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7. 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?

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Red Green
Refactor

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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

43. Copyright © Gaspar Nagy
The strategy also works for bugs
1. Capture current behavior
2. Describe bug as a scenario
3. Fix the bug

44. Copyright © Gaspar Nagy
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!
As you learn more, the scaffolding can
be removed…

45. Copyright © Gaspar Nagy
Happy maintenance!

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