TDD Overview

Test Driven Development
Embrace Uncertainty

Naresh Jain
Twitter: @nashjain
http://blogs.agilefaqs.com
Licensed Under Creative Commons by Naresh Jain
Friday, October 2, 2009 1

TDD Rhythm
Test, Code, Refactor


TDD Rhythm
Add a Test


TDD Rhythm
Add a Test

Run the Test


TDD Rhythm
Add a Test

Pass
Run the Test


TDD Rhythm
Add a Test

Pass
Run the Test

Fail


TDD Rhythm
Add a Test

Pass
Run the Test

Fail

Make a little
change


TDD Rhythm
Add a Test

Pass
Run the Test

Fail

Make a little
change

Run the Test


TDD Rhythm
Add a Test

Pass
Run the Test

Fail

Make a little
change

Fail
Run the Test


TDD Rhythm
Add a Test

Pass
Run the Test

Fail

Make a little
change

Fail
Run the Test
Pass


TDD Rhythm
Add a Test

Pass
Run the Test

Fail

Make a little
change

Fail
Run the Test
Pass

Refactor


But....


rk? e?
Ho a Wo m her
wt
oS E xtr probl
e
tar a
t? th ere
Wh Is
o? W
hen
?

ROI?
Pro
duc
tivit
y?


Continuum


Post Agile

New to Agile


Post Agile

Expert TDD
New to TDD
Practitioners

New to Agile


Me


Mumbai

We don’t travel like this


We are getting there...


Tech Talks!


Warmup Scenario


Pick one scenario and in relation to your scenario, what are the
speciﬁc observable results that will tell you that the activity has
been successfully completed?



Going out for Movie (THX sound and Digital projection)



Going out for meal (one veg.)



Going shopping ($50)
[10 Minutes]



Going shopping ($50)
[10 Minutes]

Present back to the group your ﬁndings. [3 minutes per group]


Acceptance Criteria
and Tests
A critical piece of Agile


Acceptance Criteria
Is a set of conditions that the Story must meet for it to be accepted
as complete
Is typically provided by the customer or product owner.

Is not a replacement for conversation.
Is one of the results of the conversation

Acceptance Criteria are NOT tests


Given [Precondition]

When [Actor + Action]

Then [Observable Result]


Acceptance Criteria

Examples (data + scenarios)

Acceptance Tests


Acceptance Criteria

+ Examples (data + scenarios)

Acceptance Tests


Demo
Roman Numerals to Decimal Conversion Example


1 May 1 Jul 1 Sep 1 Nov

Analysis

Design

Implementation
ERD
DFD
DD
ST


Business Facing

Are we building the right product?

Are we building the product right?

Technology/Implementation Facing


Brian Marick’s
Test Categorization
Business Facing
Supports Programming

Critique product


It Helps to think...
Business Facing
Drives Development

Critique product


Business Facing
Drives Development

Critique product
Unit Testing



Business Facing

Acceptance Testing
Drives Development

Low-ﬁ prototypes

Critique product
Unit Testing



Business Facing

Acceptance Testing Exploratory Testing
Drives Development

Low-ﬁ prototypes UI and Usability Testing

Critique product
Unit Testing



Business Facing

Acceptance Testing Exploratory Testing
Drives Development

Low-ﬁ prototypes UI and Usability Testing

Critique product
Performance Testing
Unit Testing
System Tests



Acceptance Test Driven



Story



Acceptance
Criteria

Story


Iteration

Acceptance
Criteria

Story


Iteration
Automated
Acceptance
Acceptance Tests
Criteria

Story


Iteration
Automated
Acceptance
Acceptance Tests
Criteria

Automated
Story Unit Test


Iteration
Automated
Acceptance
Acceptance Tests
Criteria

Automated
Story Unit Test

Automated
Acceptance
Tests


Iteration
Automated
Acceptance
Acceptance Tests
Criteria

Automated
Story Unit Test

Automated
Acceptance
Tests

Exploratory
Testing


Iteration
Automated
Acceptance
Acceptance Tests
Criteria

Automated
Story Unit Test

Automated
Acceptance
Tests
Acceptance
Exploratory Criteria
Testing


Iteration
Automated
Acceptance
Acceptance Tests
Criteria

Automated
Story Unit Test
Automated
UI Tests

Automated
Acceptance
Tests
Acceptance
Testing


Iteration
Automated
Acceptance P
Acceptance Tests E
Criteria R
F
O
Automated R
Story Unit Test M T
Automated E E
UI Tests N S
C T
E S
Automated
Acceptance
Tests
Acceptance
Testing


Mike Cohn’s Testing Pyramid


GUI
Tests


Small in Number
GUI Tools: Selenium, Sahi, Watir, Abbot, Frankenstein
Tests


Small in Number
Tests

Acceptance
Tests


Small in Number
Tests

Acceptance At least one per story
Tools: Fit, FitNesse, RSpec, Cucumber
Tests


Small in Number
Tests

Tests

Unit Tests


Small in Number
Tests

Tests

At least one per class or module
Tools: xUnit, TestNG
Unit Tests


Acceptance Tests View

UI
Model and Presenter

Business Tier

Data Store


Why care about TDD?


# of Lines of Code?


# of Story Points
(estimates)?


# of Features developed?


# of Features tested?


# of Features deployed?


# of Features used actively?


What about Maintenance?


Stay away from (time
hungry) debugger


Manual (monkey)
Checking by
Developers and Tester


Maintain Focus


Reduce Wastage: Hand Overs


Communication


Living, up-to-date
speciﬁcation


Communicate Design
Decisions


Learning:
Listen to your code


Baby Steps:
Slow down and think


Conﬁdence


Testable Code by Design
+ Safety Net


Loosely Coupled Design


Refactoring


Test Driven Design
Before you take the plunge


Evolutionary Design


System Metaphor


Thin Slicing


Interaction Design


Tracer Bullets


Avatars of TDD
Rule of Diversity
Distrust all claims for “One True Way”


Business Facing
Drives Development

Critique product
Inside Out

Outside In


Brian Marick’s Test Categorization


Veterinarian
Information System


Outside In: ATDD
Fitnesse Document:
Assertions: 17 right, 0 wrong, 0 ignored, 0 exceptions

com.vis.billing.fixtures.PaidCashBill

procedure details on the bill
account details
name cost
account number patient name owner name
Routine Office Visit 250
1001 Fluffy Dave Atkins
Rabies Vaccination 50
procedure details
pay Cash
name cost
patient name? owner name? account number? bill no? payment method? amount paid?
Routine Office Visit 250
Fluffy Dave Atkins 1001 1 Cash 300
Rabies Vaccination 50

bill check paid true
account number? owner name? patient name? total? paid?
1001 Dave Atkins Fluffy 300 false check total 0


Outside In: Output


ATDD: Another Example
Acceptance test:
class FluffyTest < Test::Unit::TestCase
def test_examination_and_shots
vet = Veterinarian.new
clinic = Clinic.new "Main Line health"
dave = Owner.new "Dave"
fluffy = Patient.new "Fluffy"
dave.has fluffy
visit = clinic.visit(fluffy, vet) do |v|
v.procedure "Rabies vaccination", 50
end

invoice = visit.invoice
assert_equal invoice.to_s,
<<-INVOICE
Routine visit: $200
Rabies vaccination: $50
Total: $250
INVOICE

receipt = clinic.pay_for visit, 100

assert_equal receipt.to_s,
<<-RECEIPT
Paid $100 for Routine visit
Paid $0 for Rabies vaccination
Outstanding: $150
RECEIPT
end
end


Outside In: Output


Inside Out: Unit TDD
public class ClinicTest {
private Clinic clinic = new Clinic();

@Test public class BillableTest {
public void amountOnTheReceiptShouldMatchBillableAmount() throws Exception {
Billable billable = new Billable() { private static final Account daveSAccount = new Account(101, "Dave");
public int totalAmount() { return 0; } private static final List<Service> services = new ArrayList<Service>();
};
Account dave = new Account(101, "Dave"); @Test
public void totalBillableAmountShouldBeZeroIfNoServicesAreProvided() {
Receipt rcpt = clinic.payCash(dave, billable); Billable bill = new Bill(daveSAccount, services);
assertEquals("Amount on receipt does match procedure cost", billable.totalAmount(), assertEquals("Total amount is not Zero", 0, bill.totalAmount());
rcpt.getAmount()); }
}
@Test
@Test public void totalBillableAmountShouldBeTotalOfEachServiceProvided() {
public void customerPayesBillableAmountForCashTransaction() throws Exception { services.add(new Procedure("Rabies Vaccination", 250));
final int billableAmount = 56; services.add(new Procedure("Regular office Visit", 50));
class AmountCharged { int charged; };
final AmountCharged charged = new AmountCharged(); Billable bill = new Bill(daveSAccount, services);

Billable billable = new Billable() { assertEquals("Total Amount is not 300", 300, bill.totalAmount());
public int totalAmount() { }
return billableAmount;
} @After
}; public void cleanUp() {
services.clear();
Account dave = new Account(101, "Dave") { }
public void charge(int amount) { }
charged.charged = amount;
}
};

clinic.payCash(dave, billable);
assertEquals("Account is not charged billable amount", billableAmount,charged.charged);
}
}

Inside Out: Output


Inside Out: Another Example
public class ChargeAccountForServices {
private static final Billable bill = createMock(Billable.class);
private static final Accountable account = createMock(Accountable.class);
private static final Clinic clinic = new Clinic();

@Before
public void setUp() {
reset(account); @Test
reset(bill); public void shouldHaveZeroAmountDueOnReceiptIfCompletePaymentIsMade() {
} expect(bill.amount()).andReturn(300);
replay(bill);
@Test Receipt receipt = clinic.pay(300, bill, account);
public void shouldMakePaymentsAgainstAnAccount() { verify(bill);
account.paid(bill); assertEquals(300, receipt.amount());
replay(account); assertEquals(0, receipt.amountDue());
clinic.pay(300, bill, account); }
verify(account);
} @Test
public void shouldDisplayAmountDueOnTheReceiptIfIncompletePaymentIsMade() {
expect(bill.amount()).andReturn(500);
replay(bill);
Receipt receipt = clinic.pay(300, bill, account);
verify(bill);
assertEquals(300, receipt.amount());
assertEquals(200, receipt.amountDue());
}
}


public class CreateBillForClientAccount {
private static final List<Service> services = new ArrayList<Service>();
private static final Accountable account = createMock(Accountable.class);
private Bill bill;

@Before
public void setUp() {
reset(account);
}

@Test
public void shouldThrowExceptionIfAccountIsNotDueForPayment() { @Test
expect(account.isPaymentDue()).andReturn(false); public void shouldCreateABillWithTheTotalCostOfAllTheServices() {
replay(account); IMocksControl control = createControl();
try { Service rabiesVaccination = control.createMock(Service.class);
new Bill(account, null); Service routineVisit = control.createMock(Service.class);
} catch (NoPaymentDueException e) { services.add(rabiesVaccination);
// expected services.add(routineVisit);
}
expect(account.isPaymentDue()).andReturn(true);
verify(account);
expect(account.unpaidServices()).andReturn(services);
} bill();

@After expect(rabiesVaccination.cost()).andReturn(250);
public void cleanUp() { expect(routineVisit.cost()).andReturn(50);
services.clear();
} control.replay();

assertEquals(300, bill.amount());
control.verify();
}

private void bill() throws NoPaymentDueException {
replay(account);
bill = new Bill(account, null);
verify(account);
}
}


Inside Out: Output


Coffee Vending Machine
How would you develop it?


Feedback


Visualizing Proﬁciency
Industrial Logic’s
e-learning
Automated Analysis of Lab Exercises
http://industriallogic.com/elearning/


Tools & Practices


Pair Programming


Continuous Integration


Coding Convention
+
Static Code Analysis


Checkstyle


Code Coverage


Cobertura


DB Management


Migrate4j
Bering


Questions?

naresh@agilefaqs.com


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