Do you want to learn the basics of ATDD/BDD so that you can ensure clear communications between business and development? Do you want to go beyond building to a specification, and build what is valuable instead? Agile teams often relied on user stories and acceptance criteria alone. Then more advanced teams started doing TDD (Test Driven Development) so that developers could build what they thought the business asked for. When it became clear that TDD was not enough, ATDD (Acceptance Test Driven Development) / BDD (Behaviour Test Driven Development) became popular, as they provide a common language for business and development. But building what the business wanted is not enough! With HDD (Hypothesis Driven Development), we can test our business case, just like we test our code. When we find that results don’t match our expectation, we adjust our business case to get better business results. In this presentation, we'll create several examples in ATDD/BDD and then extend out to the business case level with HDD.

1. Get What You Need,
Not What You Ask For!
An Intro to ATDD/BDD and HDD
David Bulkin
David.Bulkin@LitheSpeed.com

2. About Me
David Bulkin
VP Training Services LitheSpeed
+1.215-764-6822
David.Bulkin@lithespeed.com
@davidbulkin
www.LitheSpeed.com
www.linkedin.com/in/davidbulkin

3. Agile Enablement that’s
pragmatic, not prescriptive.

4. There is a gap of
understanding between
business and development
Development
Business

5. There is a also a gap between
what we build and what we
should build.
What we build
What we
should build

6. In this session, we want to
bridge these gaps…
…and achieve a few
other things along the
way

7. Perspective before
we start…

8. TDD
Developer builds what she thinks the
business explained.
1. Write a failing test
As a bonus, get a
better design and
automated unit
testing.
Red
1. Write a
failing test
Refactor
3. Make code better
Green
2. Make code work

9. ATDD/BDD
Use shared language to build what
the business really requested.
As a bonus get
automated
acceptance test

10. HDD
Use shared language
to better understand
what is really needed.
Learn and pivot
for real success!
1. Develop a Business Plan
Case
Learn
Ideas
Data
Build
Code
Measure
3. Adjust the Business
Goals & Approach
2. Deliver Working
System

11. 2
Testable
Example

12. Example: We’re developing an early, basic,
consumer calculator.
It’s 1972, the year of the last Apollo
mission to the moon.
7
8
9
4
5
6
1
2
3
+
0
=
Clear

13. Calculator Constraints
• 8 bits
7
8
9
4
5
6
1
2
3
+
0
=
Clear
• Can store 0 to 255.
• Unsigned, meaning that it
cannot handle negative
numbers.
• Handles only plus and minus
operations.

14. With this calculator, the user can:
•
•
•
•
Enter a number
Enter an operand
(plus or minus)
Enter another
number
Press the “=“ to
calculate
For example,
12 + 10 = 22
14 + 3 = 17
10 – 8 = 2
12
7
4
1
8
75
42
9
+
69
8
3 610
75 8 9 =
+ 1- 42*53 8 9
7 6
Cle
22
=2 5 6
ar + 1- 4*73 8 9
Cl
=2 3
ear+ 1 4* 5 6
Cl
ear
+ = 2* 3
1Cl
0
ear+ = =
Clear

15. Let’s create simple tests for the results
that do the following:
• Ensure math is correct
• Check boundaries
• Test for results our calculator
can’t handle
• Checking only for valid
sequence of input:
1. Number
2. Operand (+ or -)
3. Number
4. Equals
7
8
9
4
5
6
1
2
3
+
0
-
Clear
=

16. What I mean by valid sequence of input:
7
8
9
4
5
6
1
2
3
+
0
=
Clear
Not worried about:
• + +
• 12 - - 10
• etc.
Just valid entry sequence
to test math:
12 + 10 = 22

17. Let’s create a test of the math, assuming valid
input, and checking the boundaries of what our
calculator can handle.
Number (A)
0
Operand
+
Number (B)
0
Result?
0

18. Let’s create a test of the math, assuming valid
input, and checking the boundaries of what our
calculator can handle.
Number (A)
0
0
1
Operand
+
+
+
Number (B)
0
1
254
Result?
0
1
255

19. Now that I got
you started, do
some more
examples…

20. Let’s create a test of the math, assuming valid
input, and checking the boundaries of what our
calculator can handle.
Number (A)
0
0
1
1
255
1
1
Operand
+
+
+
+
-
Number (B)
Result?
0
1
254
255
254
0
2
0
1
255
ERR
1
1
ERR

21. t’s
Le
Organ
ize
Our

22. Happy path tests
Valid Addition
Number (A)
Operand
Number (B)
Result?
0
+
0
0
0
+
1
1
99
+
100
199
254
+
1
255
Number (B)
Result?
Valid Subtraction
Number (A)
Operand
0
-
0
0
1
-
0
1
100
-
50
50
255
-
255
0

23. Unhappy path tests
Invalid Addition
Number (A)
Operand
Number (B)
Result?
255
+
1
ERR
128
+
128
ERR
Number (B)
Result?
Invalid Subtraction
Number (A)
Operand
0
-
1
ERR
1
-
2
ERR
128
-
200
ERR

24. 2
Testable
Example

26. A ticket to Agile Land:
Agile Land Theme Park
Admit One – Ages 3 to 103
• Valid 364 Days a Year (not valid on Christmas)
• Valid for standard park opening and closing times of
9:00 AM to 9:00 PM
• Valid for one child, 3 and up, or adult
• Provides free access to most park rides
and attractions, some attractions are
additional.

27. Approximately 1,000 tickets sold and
used each month
1060
1040
1020
1000
980
960
940
920
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

29. The Solution:
Quantity
Discounts

30. Solution Quantity Discount Story:
As a member of a sizable
group
I want to purchase large
blocks of one day passes
So that I can get quantity
discounts and save money

31. Acceptance Criteria Pricing
q
q
q
Purchase <= 50 tickets at $50.00
each, from 1 to 50 inclusive
Purchase 51 to 100 tickets at $40.00
each, from 1 to 100 inclusive
Purchase 101 or more tickets at $30.00
each, from 1 to infinity

32. Let’s Create a
Testable Spec…

33. <= 50 tickets at $50.00 each, from 1 to 50 inclusive
51 to 100 tickets at $40.00 each, from 1 to 100 inclusive
101 or more tickets at $30.00 each, from 1 to infinity
Count
Price Each
Total?
0
$50
$0
1
$50
$50

34. Now that I got you
started…

35. <= 50 tickets at $50.00 each, from 1 to 50 inclusive 51 to 100
tickets at $40.00 for all tickets, from 1 to 100 inclusive 101 or
more tickets at $30.00 each for all tickets, from 1 to infinity
Count
Price Each
Total?
0
$50
$0
1
$50
$50
50
$50
$2,500
51
$40
$2,040
100
$40
$4,000
101
$30
$3,030

37. We bridged the gap of
understanding,
but…
Didn’t deliver value!
(We verified but didn’t
validate.)

38. Let’s Fix Our Acceptance
Criteria…
Acceptance Criteria Pricing
q
Purchase <= 50 tickets at $50.00 each,
from 1 to 50 inclusive
q
q
Purchase 51 to 100 tickets at $40.00
each, from 1 to 100 inclusive
Purchase 101 or more tickets at $30.00
each, from 1 to infinity

39. Acceptance Criteria Pricing
q Purchase <= 50 tickets at $50.00
each, from 1 to 50 inclusive
q Purchase 51 to 100 tickets at $40.00
each, for tickets 51 to 100 inclusive
q Purchase 101 or more tickets at $30.00
each, for tickets 101 to infinity

40. Let’s Create a
Testable Spec

41. Purchased Total for Purchased Total for Purchased Total for
Total
0 to 50
0 to 50? 51 to 100 51 to 100? 101 to ∞ 101 to ∞? Purchase
Count
0
0
$0
0
$0
0
$0
$0
1
1
$50
0
$0
0
$0
$50
50
50
$2,500
0
$0
0
$0
$2,500
51
50
$2,500
1
$40
0
$0
$2,540
100
50
$2,500
50
$2,000
0
$0
$4,500
101
50
$2,500
50
$2,000
1
$30
$4,530

42. Better!

43. But, not good
enough!

44. What’s Next?!

45. Approximately 1,000 tickets
sold and used each month
1060
1040
1020
1000
980
960
940
920
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

46. 1060
1040
1020
1000
980
960
940
920
Jan
What do we
expect next
month and
beyond?
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

47. 1060
1040
1020
1000
980
960
940
920
Do we
expect to
sell more?
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

48. $$$
What We Would Have Sold?
Price
Level
Qty
Gross?
$50.00
1,000
$50,000
Month 1
Price
Level
Qty?
Gross?
$50.00
800
$40,000
$40.00
200
$8,000
$30.00
200
$6,000
1,200
$54,000
We expect
more
gross
revenue!

49. What
we
get…
What We Would Have Sold?
Price
Level
Qty
Gross?
$50.00
1,000
$50,000
Month 1 - Projected
Month 1 - Actual
Gross?
Price
Level
Qty?
Gross?
800
$40,000
$50.00
400
$20,000
$40.00
200
$8,000
$40.00
400
$16,000
$30.00
200
$6,000
$30.00
450
$13,500
1,250
$49,500
Price
Level
Qty?
$50.00
1,200
$54,000

50. What else
should we
know?

51. How about average
net revenue from
concessions and
parking per
attendee?

52. Curren
t
Month Two
Qty?
We are selling close
1,000
1,000
to the expected
number of tickets,
Pricebut, to people who
Level
Qty?
$50.00
400
$40.00 spend less!
400
Expected
Price Level
$50.00
$30.00
Actual
Ticket Additional Additional
Gross? Per Person?
Total?
$50,000
$20
$20,000
Ticket Additional Additional
Gross? Per Person?
Total?
$20,000
$20
$8,000
$16,000
$20
$8,000
$15,000
$20
$10,000
Ticket Additional Additional
Gross? Per Person?
Total?
$20,000
$20
$8,000
$16,000
$8
$3,200
$13,500
$4
$1,800
Price Level
$50.00
$40.00
$30.00
500
1,300
Qty?
400
400
450
1,250
Gross?
$70,000
$70,000
Gross?
$28,000
$24,000
$25,000
$77,000
Gross?
$28,000
$19,200
$15,300
$62,500

53. Pivot

54. What would
you do now?

55. What else do
you need to
know?

56. Testable
examples work
for the
business too!

57. In Summary
•
User stories and acceptance criteria are easily
misunderstood, so support them with testable
examples.
•
Our business rules are not always well thought
out, so use testable examples to question,
identify, and fix bad rules
•
We often don’t understand the business impact
of what we build, so question & prove
assumptions with HDD, realign & pivot as
necessary!

58. Said Another Way…
TDD: Developer building what he/she thinks the
business wants is not enough!
ATDD/BDD: Getting on the same page about what
to build is good, and questioning what you agreed
to with ATDD/BDD is incredibly helpful,
but…

59. Think about,
align to, and
pivot towards value
with
Hypothesis-Driven
Development (HDD)

60. Thank You!
David Bulkin
VP Training Services LitheSpeed
+1.215-764-6822
David.Bulkin@lithespeed.com
@davidbulkin
www.LitheSpeed.com
www.linkedin.com/in/davidbulkin