DEV322Unit Testing Best Practices With Visual Studio 2005 Team System

Mark SeemannSenior ConsultantMicrosoft Consulting Services

Agenda

• What is a unit test?

• When to test?

• Who should test?

• How to test?

• What to test

• Choosing methodologies

• Best practices

Unit Testing Defined

• Tests a single assembly in isolation

• Volatile dependencies must be abstracted away

• Fully automated tests

• Unit tests constitute automated regression tests

• Binary results (pass or fail)

When To Write Unit Tests

• Before writing code

• Test-driven development, agile, XP, etc.

• After code is written

• Quality assurance, bug discovery, regression testing

Writing Unit Tests Before And After Writing Code

Mark Seemann

Senior Consultant

Microsoft Consulting Services

Who Should Write Unit Tests?

• Depends on the purpose of the test:

• Developers write their own tests in test-driven development

• Testers write quality assurance tests

• Developers should not write their own quality assurance tests

How To Write Tests

• What to test

• Choosing methodologies

• Best practices

What To Test

• Unit test all of your own code, except

• User interfaces

• (Web) service façades

• UI and service façades should be subjected to other types of tests

• Test only against your public API

Testing Against Public Only API

Mark Seemann

Senior Consultant

Microsoft Consulting Services

Approaches

• Pragmatic

• Formal

• Approaches can be mixed

Pragmatic Unit Testing

• Usage-oriented

• Can involve sequences of operations

• Suitable for test-driven development

Writing a Pragmatic Unit Test

Mark Seemann

Senior Consultant

Microsoft Consulting Services

Formal Unit Testing

• Systematic

• Atomic

• Check boundary conditions

• Exercise error paths

• Suitable for QA

Atomic Unit Test Structure

1. Build initial state using alternative, low-level APIs if possible

2. Invoke test target member

3. Validate results

Writing a Formal Unit Test

Mark Seemann

Senior Consultant

Microsoft Consulting Services

Best Practices

• Test cases must be independent

• Test cases must be deterministic

• Reproduce bugs as test cases

• Place tests in separate projects

• Have a test project per test target

• Use source control on test projects

Applying Best Practices with Visual Studio 2005 Team System

Mark Seemann

Senior Consultant

Microsoft Consulting Services

Summary

• Unit test all relevant libraries

• Test only public API

• Set high code coverage goal

Resources

• Unit Testing Tips: Write Maintainable Unit Tests That Will Save You Time And Tears (http://msdn.microsoft.com/msdnmag/issues/06/01/UnitTesting)

• http://blogs.msdn.com/ploeh

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Friday 10 November 10.15 – 10.45

© 2006 Microsoft Corporation. All rights reserved.This presentation is for informational purposes only.MICROSOFT MAKES NO WARRANTIES, EXPRESS OR IMPLIED, IN THIS SUMMARY.