Turning Development Outside-In

Turning

Development

Outside–In

@KevlinHenney

What We Talk About

When We Talk About

Development

@KevlinHenney

What We Talk About

When We Talk About

Requirements

@KevlinHenney

Too often we push the problem

into the background because we

are in a hurry to proceed to a

solution.

If you read most software

development texts thoughtfully,

you will see that almost everything

is about the solution; almost

nothing is about the problem.

Analysis Design Code Test



It's expensive to

know everything

up front.Kolton Andrus

You have to finish things —

that's what you learn from,

you learn by finishing things.

Neil Gaiman

SCRUM: A Pattern

Language for

Hyperproductive

Software

Development Teams

Mike Beedle, Martine Devos,

Yonat Sharon,Ken Schwaber,

and Jeff Sutherland

SCRUM Master

Sprint

Backlog

SCRUM Meetings

Demo After Sprint

SCRUM Master

Sprint

Backlog

SCRUM Meetings

Demo After Sprint

Problem

You want to balance the needs of developers to work

undisturbed and the needs of management and the

customer to see real progress, as well as control the

direction of that progress throughout the project.

Solution

Divide the project in Sprints. A Sprint is a period of

approximately 30 days in which an agreed amount of

work will be performed to create a deliverable. Each

Sprint takes a pre-allocated amount of work from the

Backlog.

Sprint

Analysis

Sprint

Design

Sprint

Code

Sprint

Test

Sprint

Analysis DesignCodeTest




Develop Develop Develop Develop

Develop

If a plot works out exactly

as you first planned, you're

not working loosely enough

to give room to your

imagination and instincts.

/ WordFriday

pantser, noun▪ Writer who writes by the seat of their pants.

▪ In contrast to a plotter, a pantser doesn't

work to (or have) an outline.

Your Customers

Do Not Mean

What They Say

Nate Jackson

I’ve never met a customer yet that

wasn’t all too happy to tell me what

they wanted—usually in great detail.

The problem is that customers don’t

always tell you the whole truth.

Nate Jackson

They generally don't lie.

They use their terms and their contexts.

They leave out significant details.

They make assumptions.

Nate Jackson

This is compounded by the fact that

many customers don’t actually know

what they want in the first place!

Nate Jackson

Systems have properties

— capabilities, features,

characteristics, etc. —

inside and out.

Development should

discover the specific

properties desired

and make them so.

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Try to leave

out the part

that readers

tend to skip.Elmore Leonard

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Stack{new, push, pop, depth, top}

GivenWhenThen

an empty stackan item is pushedit should not be empty

GivenWhenThen

an empty stackan item is pushedif it's OK with you, I think that, perhaps, it should probably not be empty, don't you think?

Omit needless words.

William Strunk and E B White

The Elements of Style

Make definite assertions.

Avoid tame, colourless, hesitating, noncommittal language.

When a sentence is made stronger, it usually becomes shorter. Thus brevity is a by-product of vigour.

William Strunk and E B White

The Elements of Style

GivenWhenThen

an empty stackan item is pushedit is not empty

GivenWhenThenAnd

an empty stackan item is pushedit has a depth of 1the top item is the item that was pushed

Given_an_empty_stack_When_an_item_is_pushed_Then_it_has_a_depth_of_1_And_the_top_item_is_the_item_that_was_pushed

Non-EmptyEmpty

depth depthtoppushpop [depth > 1]

push

pop [depth = 1]

new

public class Stack_spec{

public static class A_new_stack{

@Testpublic void is_empty()

}

public static class An_empty_stack{

@Test()public void throws_when_queried_for_its_top_item() @Test()public void throws_when_popped() @Testpublic void acquires_depth_by_retaining_a_pushed_item_as_its_top()

}

public static class A_non_empty_stack{

@Testpublic void becomes_deeper_by_retaining_a_pushed_item_as_its_top() @Testpublic void on_popping_reveals_tops_in_reverse_order_of_pushing()

}}

public classStack_spec

{public static class

A_new_stack{


}

public static class

An_empty_stack{


}

public static class

A_non_empty_stack{


}}

public classStack_spec

{public static class

A_new_stack{


}

public static class

An_empty_stack{


}

public static class

A_non_empty_stack{


}}

Systems have properties

— capabilities, features,

characteristics, etc. —

inside and out.

Functional

Operational

Developmental

We want our code

to be unit testable.

What is a unit test?

A test is not a unit test if:

▪ It talks to the database

▪ It communicates across the network

▪ It touches the file system

▪ It can't run at the same time as any of your other

unit tests

▪ You have to do special things to your environment

(such as editing config files) to run it.

Michael Feathershttp://www.artima.com/weblogs/viewpost.jsp?thread=126923

A unit test is a test of behaviour

whose success or failure is wholly

determined by the correctness of

the test and the correctness of the

unit under test.

Kevlin Henneyhttp://www.theregister.co.uk/2007/07/28/what_are_your_units/

What do we want

from unit tests?

When a unit test

passes, it shows

the code is correct.

When a unit test

fails, it shows the

code is incorrect.

As aI wantSo that

$Role$Feature$Benefit

As aI wantSo that

developer of the software$Feature$Benefit

As aI wantSo that

developer of the softwareclean code$Benefit

As aI wantSo that

customer of the software$Feature$Benefit

As aI wantSo that

user of the software$Feature$Benefit

As aI wantSo that

$Rolelogging$Benefit

As aI wantSo that

developer of the softwarelogging$Benefit

As aI wantSo that

customer of the softwarelogging$Benefit

As aI wantSo that

$Roledocumentation$Benefit

As aI wantSo that

$Rolean agile process$Benefit

As aI wantSo thatAs shown by

$Role$Feature$Benefit$Evidence

Design an architectural

space to accommodate

a specific program,

experience, or intent.