NSubstitute alternatives and similar packages
Based on the "Testing" category.
Alternatively, view NSubstitute alternatives based on common mentions on social networks and blogs.
-
Bogus
:card_index: A simple fake data generator for C#, F#, and VB.NET. Based on and ported from the famed faker.js. -
Fluent Assertions
A very extensive set of extension methods that allow you to more naturally specify the expected outcome of a TDD or BDD-style unit tests. Targets .NET Framework 4.7, as well as .NET Core 2.1, .NET Core 3.0, .NET 6, .NET Standard 2.0 and 2.1. Supports the unit test frameworks MSTest2, NUnit3, XUnit2, MSpec, and NSpec3. -
Testcontainers
A library to support tests with throwaway instances of Docker containers for all compatible .NET Standard versions. -
AutoFixture
AutoFixture is an open source library for .NET designed to minimize the 'Arrange' phase of your unit tests in order to maximize maintainability. Its primary goal is to allow developers to focus on what is being tested rather than how to setup the test scenario, by making it easier to create object graphs containing test data. -
SpecFlow
#1 .NET BDD Framework. SpecFlow automates your testing & works with your existing code. Find Bugs before they happen. Behavior Driven Development helps developers, testers, and business representatives to get a better understanding of their collaboration -
Verify
Verify is a snapshot tool that simplifies the assertion of complex data models and documents. -
NBomber
Modern and flexible load testing framework for Pull and Push scenarios, designed to test any system regardless a protocol (HTTP/WebSockets/AMQP etc) or a semantic model (Pull/Push). -
WireMock.Net
WireMock.Net is a flexible product for stubbing and mocking web HTTP responses using advanced request matching and response templating. Based on the functionality from http://WireMock.org, but extended with more functionality. -
Compare-Net-Objects
What you have been waiting for :+1: Perform a deep compare of any two .NET objects using reflection. Shows the differences between the two objects. -
Machine.Specifications
Machine.Specifications is a Context/Specification framework for .NET that removes language noise and simplifies tests. -
GenFu
GenFu is a library you can use to generate realistic test data. It is composed of several property fillers that can populate commonly named properties through reflection using an internal database of values or randomly created data. You can override any of the fillers, give GenFu hints on how to fill them. -
ArchUnitNET
A C# architecture test library to specify and assert architecture rules in C# for automated testing. -
Expecto
A smooth testing lib for F#. APIs made for humans! Strong testing methodologies for everyone! -
NBuilder
DISCONTINUED. Rapid generation of test objects in .NET [Moved to: https://github.com/nbuilder/nbuilder] -
Fine Code Coverage
Visualize unit test code coverage easily for free in Visual Studio Community Edition (and other editions too) -
NFluent
Smooth your .NET TDD experience with NFluent! NFluent is an ergonomic assertion library which aims to fluent your .NET TDD experience (based on simple Check.That() assertion statements). NFluent aims your tests to be fluent to write (with a super-duper-happy 'dot' auto-completion experience), fluent to read (i.e. as close as possible to plain English expression), but also fluent to troubleshoot, in a less-error-prone way comparing to the classical .NET test frameworks. NFluent is also directly inspired by the awesome Java FEST Fluent assertion/reflection library (http://fest.easytesting.org/) -
xBehave.net
DISCONTINUED. ✖ An xUnit.net extension for describing each step in a test with natural language. -
SpecsFor
SpecsFor is a light-weight Behavior-Driven Development framework that focuses on ease of use for *developers* by minimizing testing friction. -
Xunit.Gherkin.Quick
BDD in .NET Core - using Xunit and Gherkin (compatible with both .NET Core and .NET) -
SimpleStubs
DISCONTINUED. *SimpleStubs* is a simple mocking framework that supports Universal Windows Platform (UWP), .NET Core and .NET framework. SimpleStubs is currently developed and maintained by Microsoft BigPark Studios in Vancouver. -
Moq.Contrib.HttpClient
A set of extension methods for mocking HttpClient and IHttpClientFactory with Moq. -
#<Sawyer::Resource:0x00007f89811b9240>
:fire: A small library to help .NET developers leverage Microsoft's dependency injection framework in their Xunit-powered test projects -
SecTester
SecTester is a new tool that integrates our enterprise-grade scan engine directly into your unit tests.
CodeRabbit: AI Code Reviews for Developers
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README
NSubstitute
Visit the NSubstitute website for more information.
What is it?
NSubstitute is designed as a friendly substitute for .NET mocking libraries.
It is an attempt to satisfy our craving for a mocking library with a succinct syntax that helps us keep the focus on the intention of our tests, rather than on the configuration of our test doubles. We've tried to make the most frequently required operations obvious and easy to use, keeping less usual scenarios discoverable and accessible, and all the while maintaining as much natural language as possible.
Perfect for those new to testing, and for others who would just like to to get their tests written with less noise and fewer lambdas.
Installation
- NSubstitute package
- Optional Roslyn analysers (recommended):
- For C# projects: NSubstitute.Analyzers.CSharp
- For VB projects: NSubstitute.Analyzers.VisualBasic
Getting help
If you have questions, feature requests or feedback on NSubstitute please raise an issue on our project site. All questions are welcome via our project site, but for "how-to"-style questions you can also try StackOverflow with the [nsubstitute] tag, which often leads to very good answers from the larger programming community. StackOverflow is especially useful if your question also relates to other libraries that our team may not be as familiar with (e.g. NSubstitute with Entity Framework). You can also head on over to the NSubstitute discussion group if you prefer.
Basic use
Let's say we have a basic calculator interface:
public interface ICalculator
{
int Add(int a, int b);
string Mode { get; set; }
event Action PoweringUp;
}
<!--
ICalculator _calculator;
[SetUp]
public void SetUp() { _calculator = Substitute.For<ICalculator>(); }
-->
We can ask NSubstitute to create a substitute instance for this type. We could ask for a stub, mock, fake, spy, test double etc., but why bother when we just want to substitute an instance we have some control over?
_calculator = Substitute.For<ICalculator>();
⚠️ Note: NSubstitute will only work properly with interfaces or with virtual
members of classes. Be careful substituting for classes with non-virtual members. See Creating a substitute for more information.
Now we can tell our substitute to return a value for a call:
_calculator.Add(1, 2).Returns(3);
Assert.That(_calculator.Add(1, 2), Is.EqualTo(3));
We can check that our substitute received a call, and did not receive others:
_calculator.Add(1, 2);
_calculator.Received().Add(1, 2);
_calculator.DidNotReceive().Add(5, 7);
If our Received() assertion fails, NSubstitute tries to give us some help as to what the problem might be:
NSubstitute.Exceptions.ReceivedCallsException : Expected to receive a call matching:
Add(1, 2)
Actually received no matching calls.
Received 2 non-matching calls (non-matching arguments indicated with '*' characters):
Add(1, *5*)
Add(*4*, *7*)
We can also work with properties using the Returns syntax we use for methods, or just stick with plain old property setters (for read/write properties):
_calculator.Mode.Returns("DEC");
Assert.That(_calculator.Mode, Is.EqualTo("DEC"));
_calculator.Mode = "HEX";
Assert.That(_calculator.Mode, Is.EqualTo("HEX"));
NSubstitute supports argument matching for setting return values and asserting a call was received:
_calculator.Add(10, -5);
_calculator.Received().Add(10, Arg.Any<int>());
_calculator.Received().Add(10, Arg.Is<int>(x => x < 0));
We can use argument matching as well as passing a function to Returns() to get some more behaviour out of our substitute (possibly too much, but that's your call):
_calculator
.Add(Arg.Any<int>(), Arg.Any<int>())
.Returns(x => (int)x[0] + (int)x[1]);
Assert.That(_calculator.Add(5, 10), Is.EqualTo(15));
Returns() can also be called with multiple arguments to set up a sequence of return values.
_calculator.Mode.Returns("HEX", "DEC", "BIN");
Assert.That(_calculator.Mode, Is.EqualTo("HEX"));
Assert.That(_calculator.Mode, Is.EqualTo("DEC"));
Assert.That(_calculator.Mode, Is.EqualTo("BIN"));
Finally, we can raise events on our substitutes (unfortunately C# dramatically restricts the extent to which this syntax can be cleaned up):
bool eventWasRaised = false;
_calculator.PoweringUp += () => eventWasRaised = true;
_calculator.PoweringUp += Raise.Event<Action>();
Assert.That(eventWasRaised);
Building
NSubstitute and its tests can be compiled and run using Visual Studio and Visual Studio for Mac. Note that some tests are marked [Pending]
and are not meant to pass at present, so it is a good idea to exclude tests in the Pending category from test runs.
There are also build scripts in the ./build
directory for command line builds, and CI configurations in the project root.
To do full builds you'll also need Ruby, as the jekyll gem is used to generate the website.
Other libraries you may be interested in
- Moq: the original Arrange-Act-Assert mocking library for .NET, and a big source of inspiration for NSubstitute.
- FakeItEasy: another modern mocking library for .NET. If you're not sold on NSubstitute's syntax, try FIE!
- substitute.js: a mocking library for TypeScript inspired by NSubstitute's syntax (
@fluffy-spoon/substitute
on NPM)