A brief introduction to test doubles and mocking frameworks

Unit testing goals Verification Feedback Speed Focus Isolation

Verification

Feedback Speed

Focus

Isolation

Test Doubles 4 types of test double Dummy – We just pass it round and don’t do anything with it Fake – Working implementations but take shortcuts Stubs – Canned answers to expected calls Mocks – Pre programmed with responses and expectations that certain calls should be made

4 types of test double

Dummy – We just pass it round and don’t do anything with it

Fake – Working implementations but take shortcuts

Stubs – Canned answers to expected calls

Mocks – Pre programmed with responses and expectations that certain calls should be made

Why? Feedback cycle needs to be as small as possible to be useful We need to remove pain points from being necessary Database calls UI Third party libraries We can remove reliance on the rest of the code being complete before knowing the current unit works

Feedback cycle needs to be as small as possible to be useful

We need to remove pain points from being necessary

Database calls

UI

Third party libraries

We can remove reliance on the rest of the code being complete before knowing the current unit works

Mocking frameworks Provide a repeatable way to set up mocks/stubs/fakes with little code cost. Test logic can stay within test We can develop as we test and get immediate results (TDD)

Provide a repeatable way to set up mocks/stubs/fakes with little code cost.

Test logic can stay within test

We can develop as we test and get immediate results (TDD)

Rhino.Mocks One of the most mature and feature complete mocking frameworks Uses castle remoting to mock calls Not able to mock static or sealed calls Fast Record/Replay Syntax Lots of help and code examples available Open Source

One of the most mature and feature complete mocking frameworks

Uses castle remoting to mock calls

Not able to mock static or sealed calls

Fast

Record/Replay Syntax

Lots of help and code examples available

Open Source

Typemock Isolator Mature and fully featured Uses IL Generation Can mock static classes and calls Can chain events Commercial licence available for full feature set and support Main commercial mocking framework so features ++

Mature and fully featured

Uses IL Generation

Can mock static classes and calls

Can chain events

Commercial licence available for full feature set and support

Main commercial mocking framework so features ++

Moq New Kid on the block .net 3.5 only No record/replay semantics, just expectations Less code clutter to tests Not feature complete In active development Open source

New Kid on the block

.net 3.5 only

No record/replay semantics, just expectations

Less code clutter to tests

Not feature complete

In active development

Open source

How? It’s time to code

It’s time to code

Links Rhino Mocks: http://www.ayende.com/projects/rhino-mocks.aspx Typemock: http://www.typemock.com/ Moq: http://code.google.com/p/moq Me: http://www.bgeek.net [email_address] http://www.twitter.com/buildmaster

Rhino Mocks: http://www.ayende.com/projects/rhino-mocks.aspx

Typemock: http://www.typemock.com/

Moq: http://code.google.com/p/moq

Me: http://www.bgeek.net [email_address] http://www.twitter.com/buildmaster