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Mocking .NET Without Hurting Its Feelings (NEWCC Mar 2018)
Mocking .NET Without Hurting Its Feelings
Northeast Wisconsin
Code Camp
March 24th, 2018
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Please be aware that I have received a Community license, at no cost to me, for Typemock Isolator, due to involvement in the development community and my writing/speaking on mocking topics.
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wrightfully.com/mocktalk
John M. Wright
class DependenciesHog
{
public string foo
{
get;
set;
}
private void bar(int x)
{
//I do stuff
}
public event BigEvent EventHorizon;
private void SpaceFiller()
{
while (true)
{
LookInteresting();
}
}
}
My test
value
john@wrightfully.com
Why use a Mocking Framework?
Using Hand-Crafted, Artisanal Mocks
@wright2tweet
www.wrightfully.com
© Copyright 2018 John M. Wright
mock
test double
What can they do?
mock.VerifyAllExpectations();
mock.AssertWasCalled(x => x.MyMethod());
mock
vs
stub
vs
stub
A rose by any other name
would smell as sweet
work about the same
mock types
How do they do it?
Per 5 Build Servers:
as of 2018-01-22
Code Examples (aka: What can you do?)
Code being tested
Example Test using a Mock
Using Moq Syntax
Unconstrained Code Examples
Typemock Syntax
Code being tested
MS Fakes Syntax
Unconstrained Frameworks:
Make Your Own Man-In-The-Middle Attack
Constrained Frameworks:
Limitations of Class Inheritance
Constrained Frameworks:
Class Inheritance On-Demand
internal types & members
Mocking Internal Types/Members
AssemblyInfo.cs
[assembly: InternalsVisibleTo("Your.TestAssembly")]
[assembly: InternalsVisibleTo("DynamicProxyGenAssembly2, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c547cac37abd99c8db225ef2f6c8a3602f3b3606cc9891605d02baa56104f4cfc0734aa39b93bf7852f7d9266654753cc297e7d2edfe0bac1cdcf9f717241550e0a7b191195b7667bb4f64bcb8e2121380fd1d9d46ad2d92d2d15605093924cceaf74c4861eff62abf69b9291ed0a340e113be11e6a7d3113e92484cf7045cc7")]
sealed types
Generated Classes:
- Inherit / Extend Mocked Type
- Override virtual/abstract members
- Check for configured stubs/mocks
- Save details for later verification
- Take action based on configuration
ICorProfilerInfo::
SetILFunctionBody
Hijacked Code:
- Can change Behavior of ANY Type/Member
- Doesn't rely on inheritance
- Everything gets JIT'd, so anything can be mocked!
- Injected code will:
- Check for configured stubs/mocks
- Save details for later verification
- Take action based on configuration
The New Guy In Town
$ $ $
DateTime.Now
All that, plus:
- public
- internal
- methods
- properties
- events
- static
- sealed
- private
- .NET libs
- 3rd Party libs (Sharepoint)
Mock
What can
I expect?
private members
JITCompilationStarted
dynamic
Unconstrained
Constrained
public types & members
More Info @
wrightfully.com/mocktalk
methods, properties, events
- Open source
- No extra software needed
- Limited commercial support
- May require design compromises
- Proprietary (closed source)
- Some require profiler application / VS plugin
- Commercial support
class DatabaseConnection
{
}
substitute
http://mimiandeunice.com/2011/07/19/expectations/
static types & members
shim
class AnotherOne
{
}
Using A Mocking Framework
Custom Mocks
File I/O
$$$
UI
$$
Integration
$
Unit Tests
FREE
158 members!
partial
Unconstrained
.VerifyAll()
class DatabaseConnection
{
}
Great for testing "legacy" code.
Best fit for code written with testing in mind.
Class Being Tested
interfaces
fake
Tests
virtual / abstract members
strict
Constrained