Poser allows you to replace any .NET method (including static and non-virtual) with a delegate. It is similar to Microsoft Fakes but unlike it Poser is implemented entirely in managed code (Reflection Emit API). Everything occurs at runtime and in-memory, no unmanaged Profiling APIs and no file system pollution with re-written assemblies.
Poser is cross platform and runs anywhere .NET is supported. It targets .NET Standard 2.0 so it can be used across .NET platforms including .NET Framework, .NET Core, Mono and Xamarin. See version compatibility table here.
Available on NuGet
Visual Studio:
PM> Install-Package Poser
.NET Core CLI:
dotnet add package Poser
Poser gives you the ability to create shims by way of the Shim
class. Shims are basically objects that let you specify the method you want to replace as well as the replacement delegate. Delegate signatures (arguments and return type) must match that of the methods they replace. The Is
class is used to create instances of a type and all code you want to apply your shims to is isolated using the PoseContext
class.
using Pose;
Shim consoleShim = Shim.Replace(() => Console.WriteLine(Is.A<string>())).With(
delegate (string s) { Console.WriteLine("Hijacked: {0}", s); });
using Pose;
Shim dateTimeShim = Shim.Replace(() => DateTime.Now).With(() => new DateTime(2004, 4, 4));
using Pose;
Shim setterShim = Shim.Replace(() => Console.Title, true).With((string title) => { Console.Title = "My Title"; });
using Pose;
class MyClass
{
public int MyProperty { get; set; }
public void DoSomething() => Console.WriteLine("doing someting");
}
Shim classPropShim = Shim.Replace(() => Is.A<MyClass>().MyProperty).With((MyClass @this) => 100);
using Pose;
Shim classPropShim = Shim.Replace(() => Is.A<MyClass>().MyProperty, true).With((MyClass @this, int prop) => { @this.MyProperty = prop * 10; });
using Pose;
Shim ctorShim = Shim.Replace(() => new MyClass()).With(() => new MyClass() { MyProperty = 10 });
using Pose;
Shim classShim = Shim.Replace(() => Is.A<MyClass>().DoSomething()).With(
delegate (MyClass @this) { Console.WriteLine("doing someting else"); });
Note: The first argument to an instance method replacement delegate is always the instance of the class
using Pose;
MyClass myClass = new MyClass();
Shim myClassShim = Shim.Replace(() => myClass.DoSomething()).With(
delegate (MyClass @this) { Console.WriteLine("doing someting else with myClass"); });
using Pose;
Shim structShim = Shim.Replace(() => Is.A<MyStruct>().DoSomething()).With(
delegate (ref MyStruct @this) { Console.WriteLine("doing someting else"); });
Note: You cannot shim methods on specific instances of Value Types
var operatorShim = Shim.Replace(() => Is.A<TimeSpan>() + Is.A<TimeSpan>()).With(
delegate(TimeSpan l, TimeSpan r) { return TimeSpan.Zero; });
// This block executes immediately
PoseContext.Isolate(() =>
{
// All code that executes within this block
// is isolated and shimmed methods are replaced
// Outputs "Hijacked: Hello World!"
Console.WriteLine("Hello World!");
// Outputs "4/4/04 12:00:00 AM"
Console.WriteLine(DateTime.Now);
// Outputs "doing someting else"
new MyClass().DoSomething();
// Outputs "doing someting else with myClass"
myClass.DoSomething();
// Outputs '00:00:00'
Console.WriteLine(TimeSpan.FromDays(1) + TimeSpan.FromSeconds(2));
}, consoleShim, dateTimeShim, classPropShim, classShim, myClassShim, structShim, operatorShim);
Operator shimming requires that the class/struct overloads the operator in question.
Poser supports shimming operators of the following kind:
+x
-x
!x
~x
x + y
x - y
x / y
x % y
x & y
x | y
x ^ y
x << y
x >> y
x == y
x != y
x < y
x > y
x <= y
x >= y
In addition to this, both implicit and explicit conversion operators are supported.
Shimming of the following operators is not supported:
true
and false
because I cannot find a good way to express the operation in an expression tree.x >>> y
because expression trees cannot contain this operator. This is a limitation on the part of the compiler.++
and --
because these cannot be expressed in an expression tree.System.Reflection.TargetInvocationException
.If you find a bug or have a feature request, please report them at this repository's issues section. Contributions are highly welcome, however, except for very small changes kindly file an issue and let's have a discussion before you open a pull request.
This project is licensed under the MIT license. See the LICENSE file for more info.