What are mocking frameworks you’ve used with .NET? Examples?

Question

ICSM Computer · Answer

Mocking frameworks are essential in .NET unit testing for isolating dependencies and simulating behavior of external components like services, databases, or APIs. Here are some of the
most popular mocking frameworks used with .NET, along with 
examples:
1. Moq (Most Popular)
Moq is a widely used and easy-to-learn mocking library for .NET.
Installation
dotnet add package Moq
Example – Mocking a service
Interface:
public interface IUserService
{
    string GetUserName(int id);
}
Test using Moq:
var mock = new Mockandlt;IUserServiceandgt;();
mock.Setup(s =andgt; s.GetUserName(1)).Returns("Anna");
var controller = new UsersController(mock.Object);
var result = controller.GetUserName(1); // Should return "Anna"
Assert.Equal("Anna", result);
2. NSubstitute
A simpler and more intuitive alternative to Moq.
Installation
dotnet add package NSubstitute
Example:
var userService = Substitute.Forandlt;IUserServiceandgt;();
userService.GetUserName(1).Returns("Anna");
var result = userService.GetUserName(1);
Assert.Equal("Anna", result);
3. FakeItEasy
Very readable syntax; good for newcomers.
Installation
dotnet add package FakeItEasy
Example:
var service = A.Fakeandlt;IUserServiceandgt;();
A.CallTo(() =andgt; service.GetUserName(1)).Returns("Anna");
var result = service.GetUserName(1);
Assert.Equal("Anna", result);
4. JustMock (Telerik)
Supports mocking non-virtual members, static, and
sealed classes.Has both free and paid editions.
Example:
var service = Mock.Createandlt;IUserServiceandgt;();
Mock.Arrange(() =andgt; service.GetUserName(1)).Returns("Anna");
Assert.Equal("Anna", service.GetUserName(1));
5. Microsoft Fakes (only in Visual Studio Enterprise)
Can mock static and sealed classes.Available in VS Enterprise only.Uses shim and stub concepts.
Summary Table
Framework
Syntax Style
Can Mock Sealed/Static
Popularity
Notes
Moq
Fluent
(only interfaces/virtual)
⭐⭐⭐⭐⭐
Most common, widely used
NSubstitute
Natural
Yes
⭐⭐⭐⭐
Simple and clean syntax
FakeItEasy
Natural
Yes
⭐⭐⭐⭐
Very readable
JustMock
Fluent
(paid version)
⭐⭐⭐
Paid version powerful
Microsoft Fakes
Stub/Shim
Yes
⭐⭐
Only in VS Enterprise

interview

What are mocking frameworks you’ve used with .NET? Examples?

ICSM Computer

Can you answer this question?

1 Answers

1. Moq (Most Popular)

Installation

Example – Mocking a service

Interface:

Test using Moq:

2. NSubstitute

Installation

Example:

3. FakeItEasy

Installation

Example:

4. JustMock (Telerik)

Example:

5. Microsoft Fakes (only in Visual Studio Enterprise)

Summary Table

Liked By

Framework	Syntax Style	Can Mock Sealed/Static	Popularity	Notes
Moq	Fluent	(only interfaces/virtual)	⭐⭐⭐⭐⭐	Most common, widely used
NSubstitute	Natural	Yes	⭐⭐⭐⭐	Simple and clean syntax
FakeItEasy	Natural	Yes	⭐⭐⭐⭐	Very readable
JustMock	Fluent	(paid version)	⭐⭐⭐	Paid version powerful
Microsoft Fakes	Stub/Shim	Yes	⭐⭐	Only in VS Enterprise