xUnit Test Patterns

Gerard Meszaros is Chief Scientist and Senior Consultant at ClearStream Consulting, a Calgary-based consultancy specializing in agile development. He has more than a decade of experience with automated unit testing frameworks and is a leading expert in test automation patterns, refactoring of software and tests, and design for testability.

Visual Summary of the Pattern Language xvii Foreword xix Preface xxi Acknowledgments xxvi Introduction xxix Refactoring a Test xlv PART I: The Narratives 1 Chapter 1 A Brief Tour 3 About This Chapter 3

The Simplest Test Automation Strategy That Could Possibly Work 3

Development Process 4

Customer Tests 5

Unit Tests 6

Design for Testability 7

Test Organization 7

What's Next? 8

Chapter 2 Test Smells 9 About This Chapter 9

An Introduction to Test Smells 9

What's a Test Smell? 10

Kinds of Test Smells 10

What to Do about Smells? 11

A Catalog of Smells 12

The Project Smells 12

The Behavior Smells 13

The Code Smells 16

What's Next? 17

Chapter 3 Goals of Test Automation 19 About This Chapter 19

Why Test? 19

Economics of Test Automation 20

Goals of Test Automation 21

Tests Should Help Us Improve Quality 22

Tests Should Help Us Understand the SUT 23

Tests Should Reduce (and Not Introduce) Risk 23

Tests Should Be Easy to Run 25

Tests Should Be Easy to Write and Maintain 27

Tests Should Require Minimal Maintenance as

the System Evolves Around Them 29

What's Next? 29

Chapter 4 Philosophy of Test Automation 31 About This Chapter 31

Why Is Philosophy Important? 31

Some Philosophical Differences 32

Test First or Last? 32

Tests or Examples? 33

Test-by-Test or Test All-at-Once? 33

Outside-In or Inside-Out? 34

State or Behavior Verification? 36

Fixture Design Upfront or Test-by-Test? 36

When Philosophies Differ 37

My Philosophy 37

What's Next? 37

Chapter 5 Principles of Test Automation 39 About This Chapter 39

The Principles 39

What's Next? 48

Chapter 6 Test Automation Strategy 49 About This Chapter 49

What's Strategic? 49

Which Kinds of Tests Should We Automate? 50

Per-Functionality Tests 50

Cross-Functional Tests 52

Which Tools Do We Use to Automate Which Tests? 53

Test Automation Ways and Means 54

Introducing xUnit 56

The xUnit Sweet Spot 58

Which Test Fixture Strategy Do We Use? 58

What Is a Fixture? 59

Major Fixture Strategies 60

Transient Fresh Fixtures 61

Persistent Fresh Fixtures 62

Shared Fixture Strategies 63

How Do We Ensure Testability? 65

Test Last--At Your Peril 65

Design for Testability--Upfront 65

Test-Driven Testability 66

Control Points and Observation Points 66

Interaction Styles and Testability Patterns 67

Divide and Test 71

What's Next? 73

Chapter 7 xUnit Basics 75 About This Chapter 75

An Introduction to xUnit 75

Common Features 76

The Bare Minimum 76

Defining Tests 76

What's a Fixture? 78

Defining Suites of Tests 78

Running Tests 79

Test Results 79

Under the xUnit Covers 81

Test Commands 82

Test Suite Objects 82

xUnit in the Procedural World 82

What's Next? 83

Chapter 8 Transient Fixture Management 85 About This Chapter 85

Test Fixture Terminology 86

What Is a Fixture? 86

What Is a Fresh Fixture? 87

What Is a Transient Fresh Fixture? 87

Building Fresh Fixtures 88

In-line Fixture Setup 88

Delegated Fixture Setup 89

Implicit Fixture Setup 91

Hybrid Fixture Setup 93

Tearing Down Transient Fresh Fixtures 93

What's Next? 94

Chapter 9 Persistent Fixture Management 95 About This Chapter 95

Managing Persistent Fresh Fixtures 95

What Makes Fixtures Persistent? 95

Issues Caused by Persistent Fresh Fixtures 96

Tearing Down Persistent Fresh Fixtures 97

Avoiding the Need for Teardown 100

Dealing with Slow Tests 102

Managing Shared Fixtures 103

Accessing Shared Fixtures 103

Triggering Shared Fixture Construction 104

What's Next? 106

Chapter 10 Result Verification 107 About This Chapter 107

Making Tests Self-Checking 107

Verify State or Behavior? 108

State Verification 109

Using Built-in Assertions 110

Delta Assertions 111

External Result Verification 111

Verifying Behavior 112

Procedural Behavior Verification 113

Expected Behavior Specification 113

Reducing Test Code Duplication 114

Expected Objects 115

Custom Assertions 116

Outcome-Describing Verification Method 117

Parameterized and Data-Driven Tests 118

Avoiding Conditional Test Logic 119

Eliminating "if" Statements 120

Eliminating Loops 121

Other Techniques 121

Working Backward, Outside-In 121

Using Test-Driven Development to

Write Test Utility Methods 122

Where to Put Reusable Verification Logic? 122

What's Next? 123

Chapter 11 Using Test Doubles 125 About This Chapter 125

What Are Indirect Inputs and Outputs? 125

Why Do We Care about Indirect Inputs? 126

Why Do We Care about Indirect Outputs? 126

How Do We Control Indirect Inputs? 128

How Do We Verify Indirect Outputs? 130

Testing with Doubles 133

Types of Test Doubles 133

Providing the Test Double 140

Configuring the Test Double 141

Installing the Test Double 143

Other Uses of Test Doubles 148

Endoscopic Testing 149

Need-Driven Development 149

Speeding Up Fixture Setup 149

Speeding Up Test Execution 150

Other Considerations 150

What's Next? 151

Chapter 12 Organizing Our Tests 153 About This Chapter 153

Basic xUnit Mechanisms 153

Right-Sizing Test Methods 154

Test Methods and Testcase Classes 155

Testcase Class per Class 155

Testcase Class per Feature 156

Testcase Class per Fixture 156

Choosing a Test Method Organization Strategy 158

Test Naming Conventions 158

Organizing Test Suites 160

Running Groups of Tests 160

Running a Single Test 161

Test Code Reuse 162

Test Utility Method Locations 163

TestCase Inheritance and Reuse 163

Test File Organization 164

Built-in Self-Test 164

Test Packages 164

Test Dependencies 165

What's Next? 165

Chapter 13 Testing with Databases 167 About This Chapter 167

Testing with Databases 167

Why Test with Databases? 168

Issues with Databases 168

Testing without Databases 169

Testing the Database 171

Testing Stored Procedures 172

Testing the Data Access Layer 172

Ensuring Developer Independence 173

Testing with Databases (Again!) 173

What's Next? 174

Chapter 14 A Roadmap to Effective Test Automation 175 About This Chapter 175

Test Automation Difficulty 175

Roadmap to Highly Maintainable Automated Tests 176

Exercise the Happy Path Code 177

Verify Direct Outputs of the Happy Path 178

Verify Alternative Paths 178

Verify Indirect Output Behavior 179

Optimize Test Execution and Maintenance 180

What's Next? 181

PART II: The Test Smells 183 Chapter 15 Code Smells 185 Obscure Test 186

Conditional Test Logic 200

Hard-to-Test Code 209

Test Code Duplication 213

Test Logic in Production 217

Chapter 16 Behavior Smells 223 Assertion Roulette 224

Erratic Test 228

Fragile Test 239

Frequent Debugging 248

Manual Intervention 250

Slow Tests 253

Chapter 17 Project Smells 259 Buggy Tests 260

Developers Not Writing Tests 263

High Test Maintenance Cost 265

Production Bugs 268

PART III: The Patterns 275 Chapter 18 Test Strategy Patterns 277 Recorded Test 278

Scripted Test 285

Data-Driven Test 288

Test Automation Framework 298

Minimal Fixture 302

Standard Fixture 305

Fresh Fixture 311

Shared Fixture 317

Back Door Manipulation 327

Layer Test 337

Chapter 19 xUnit Basics Patterns 347 Test Method 348

Four-Phase Test 358

Assertion Method 362

Assertion Message 370

Testcase Class 373

Test Runner 377

Testcase Object 382

Test Suite Object 387

Test Discovery 393

Test Enumeration 399

Test Selection 403

Chapter 20 Fixture Setup Patterns 407 In-line Setup 408

Delegated Setup 411

Creation Method 415

Implicit Setup 424

Prebuilt Fixture 429

Lazy Setup 435

Suite Fixture Setup 441

Setup Decorator 447

Chained Tests 454

Chapter 21 Result Verification Patterns 461 State Verification 462

Behavior Verification 468

Custom Assertion 474

Delta Assertion 485

Guard Assertion 490

Unfinished Test Assertion 494

Chapter 22 Fixture Teardown Patterns 499 Garbage-Collected Teardown 500

Automated Teardown 503

In-line Teardown 509

Implicit Teardown 516

Chapter 23 Test Double Patterns 521 Test Double 522

Test Stub 529

Test Spy 538

Mock Object 544

Fake Object 551

Configurable Test Double 558

Hard-Coded Test Double 568

Test-Specific Subclass 579

Chapter 24 Test Organization Patterns 591 Named Test Suite 592

Test Utility Method 599

Parameterized Test 607

Testcase Class per Class 617

Testcase Class per Feature 624

Testcase Class per Fixture 631

Testcase Superclass 638

Test Helper 643

Chapter 25 Database Patterns 649 Database Sandbox 650

Stored Procedure Test 654

Table Truncation Teardown 661

Transaction Rollback Teardown 668

Chapter 26 Design-for-Testability Patterns 677 Dependency Injection 678

Dependency Lookup 686

Humble Object 695

Test Hook 709

Chapter 27 Value Patterns 713 Literal Value 714

Derived Value 718

Generated Value 723

Dummy Object 728

PART IV: Appendixes 733 Appendix A Test Refactorings 735 Appendix B xUnit Terminology 741 Appendix C xUnit Family Members 747 Appendix D Tools 753 Appendix E Goals and Principles 757 Appendix F Smells, Aliases, and Causes 761 Appendix G Patterns, Aliases, and Variations 767 Glossary 785 References 819 Index 835