how to become a 'specification by example' rocket scientist

Copyright © 2015 Equinox Limited

How to become a 'specification by example' rocket scientist

Kirsten Eriksen, Senior ConsultantBen Hughes, Systems Analyst

Copyright © 2015 Equinox Limited

Equinox IT is New Zealand’s leading independent IT consultancy, delivering software development, consulting and training services.

Established in 1995, we inject fresh thinking to solve tough business problems.

Equinox IT has over 60 staff based in Wellington and Auckland.

About Equinox IT

Copyright © 2015 Equinox Limited 3

Journey from Tester to Analyst


The tester, simplified

• Test one thing at a time

• A poor test triggers multiple failure states• Enter a credit card with an invalid date and no

card holder details


The analyst, simplified

• Describe one thing at a time

• A poor requirement muddies the distinction between features• The system must be responsive


Finding common ground

• Increase focus on early collaboration

• Analysis of a requirement taking the form of a test case


Specification by Example basics


Why Specification by Example

• A way to explicitly discuss assumptions and drive out actual requirements

• Just one approach


Why Specification by Example

• The earlier a problem is found, the cheaper it is to resolve

Design Implementation Testing0

2

4

6

8

10

12

14

16

Relative cost to fix

Phase Defect is foundData sourced from IBM Systems Sciences Institute


Acronym Driven Development

Images sourced from freepik.com

ATDDAcceptance Test Driven Development

BDDBehaviour Driven Development

FDDFeature-Driven Development


What is Specification by Example?

• Realistic examples over abstract statements

• A collaborative approach

• A facilitated approach


How Specification by Example can help

• “We need to give people something complete enough to complain about”

• Business Analysts can get caught in a world where they can never be wrong – which leads to them becoming a bottleneck


Specification by Example approaches

• Table• Can be similar to decision tables in format

• Scenarios• Given / When / Then format• Can be similar to business rules in format



• Table, useful for describing inputs and outputs

Order total ESA member? Free shipping?

$10M Yes Yes

$10M No Yes

$5M Yes Yes

$5M No No



• Scenario, useful for work flows

Given I have logged inAnd I have add an item to a consignmentWhen I select to proceed to checkoutThen the items will be listed for confirmationAnd I am prompted to select a payment method

Preconditions

Trigger

Outcomes


Specification by Example – How it Fits in.


How to use Specification by Example

• Atomic• Complete• Consistent• Concise• Feasible

• Unambiguous• Testable• Understandable• Prioritised

• BABOK – 7.2.4 Quality conditions for a requirement:


Which approach when?

• Table• If it’s a calculation• If showing the impact of one on many

• Given / When / Then• If a table would be too big or complex• If you are describing a flow


Using Specification by Example: Practical Examples


Calculations – The Bad Way

Given that an order has been made by a new customer When the price of the order is over $20 Then a discount of $5 is applied

Given that an order has been made by a new customer When the price of the order is over $100 Then a discount of $33.33 is applied


Calculations - Instead try:

Customer Type Value of Order Discount

New Customer >$20 25%

New Customer >$100 33%

Existing Customer >$20 0%

Existing Customer >$100 10%


Tangled Table – The Bad Way

Credit card name

Credit card expiry Credit card number

Credit card type Accepted?

A Jones 12/15 1234-1234-1234-1234 Visa Yes

K Smith 1/17 2345-2345-2345-2345 Amex No

G Williams 4/16 18954254 Visa No

R Penfold 8/15 3456-3456-3456-3456 Master Card No

M Matthews 2/16 123456789 GE Card No

P Andrews 10/15 9876-H582-G156-K157 Visa No

D McDonald 11/14 CRED-ITCA-RDSS-UCK! Amex No


Tangled Table – Instead Try:

Given that a credit card has been provided for paymentWhen the credit card is validThen the payment will be accepted

Valid is defined as: - Having a name that is accepted by the credit card service- Having an expiry date that is equal to or after the current month - Having a number that:

- Consists entirely of numerals- Is 16 characters long- Contains 4 sets of sequential numbers

- Is of a type that is either MasterCard or Visa


Non-Atomic Given / When / Then – The Bad Way

Given that a purchase has been submittedWhen the purchase has been validated and acceptedThen send the customer the details of the orderAND update the stock inventoryAND send the information to the warehouse for fulfilment


Non-Atomic Given / When / ThenInstead Try:

Given that a purchase has been submittedWhen the purchase has been validated and acceptedThen send the customer the details of the order

Given that a purchase has been submittedWhen the purchase has been validated and acceptedThen update the stock inventory

Given that a purchase has been submittedWhen the purchase has been validated and acceptedThen send the information to the warehouse for fulfilment


Multiple versions of input result in the same output – The Bad WayItem type Quantity Result

Rocket Ship >1 Accept

Spacesuit >1 Accept

Space Helmet >1 AcceptSpace Rocks >1 AcceptSpace Boots >1 AcceptSpace Food >1 AcceptGravity Belt >1 AcceptAnti-matter Ray >1 Accept


Multiple versions of input result in the same output - Instead Try:

Given that a quantity of items have been requestedWhen Validating the quantityThen numbers greater than one (1) are accepted


Quantities – whole numbers vs partial- The Bad Way

Quantity requested Result

1 Accept

1.1 Fail

1.75 Fail-2 Fail

3.89 Fail

1,000,000 Accept

3,768,825.976 Fail

0.876328 Fail


Quantities – whole numbers vs partialInstead Try: Given that a quantity of rocketships have been requestedWhen Validating the quantityThen only positive whole numbers can be accepted

Given that a quantity of rocketships have been requestedWhen the quantity is not a positive whole numberThen display an error


Injecting fresh thinking to solve tough business problems.