# Moq vs NSubstitute Code Comparisons > In this article, we compare how to do things in Moq versus NSubstitute. - URL: https://blog.nimblepros.com/blogs/moq-vs-nsubstitute-code-comparisons/ - Author: [Sarah Dutkiewicz](https://blog.nimblepros.com/authors/sadukie/) - Published: 2023-08-17 - Categories: [Software Development](https://blog.nimblepros.com/categories/software-development/) - Publisher: [NimblePros](https://blog.nimblepros.com/) --- As you move from Moq to NSubstitute, you may wonder how they differ code-wise. In a recent lunch-n-learn discussion, [Scott DePouw](/author/scott) walked us through how the code differs between them, so let's see his findings. The code is available in our [NimblePros/moq-to-nsubstitute-guide repository](https://github.com/NimblePros/moq-to-nsubstitute-guide). In this article: - [Creating a mock widget](#creating-a-mock-widget) - [Verifying method calls](#verifying-method-calls) - [Verify a call was made](#verify-a-call-was-made) - [Verify a call was made exactly once](#verify-a-call-was-made-exactly-once) - [Verify a call was never made](#verify-a-call-was-never-made) - [Verify a call for a specific number of calls](#verify-a-call-for-a-specific-number-of-calls) - [Verify no other calls](#verify-no-other-calls) - [Verify async calls](#verify-async-calls) - [Setting up arguments in mocked method calls](#setting-up-arguments-in-mocked-method-calls) - [Accessing a mock's calls and arguments](#accessing-a-mocks-calls-and-arguments) - [Setting up exceptions](#setting-up-exceptions) - [Conclusion](#conclusion) ## Creating a mock widget In Moq, your code to create a fake `Widget()` may look like this: ```csharp _mock.Setup(factory => factory.Create()).Returns(new Widget()); ``` To create a fake `Widget()` in NSubstitute, the code will look like this: ```csharp _mock.Create().Returns(new Widget()); ``` What if you are creating a widget asynchronously? Your Moq code may look like this: ```csharp _mock.Setup(client => client.GetAsync()).ReturnsAsync("Foo"); ``` The NSubstitute code to create a widget asynchronously will look like this: ```csharp _mock.GetAsync().Returns("Foo"); ``` ## Verifying method calls Suppose you want to ensure that a method is called. These are some scenarios that you may want to check. ### Verify a call was made This is the code in Moq to verify that a call was made: ```csharp _mock.Verify(factory => factory.Create()); ``` This is the equivalent in NSubstitute to verify that a call was made: ```csharp _mock.Received().Create(); ``` ### Verify a call was made exactly once If you want to verify that a call to a method was made exactly one time, this is how you do it in Moq: ```csharp _mock.Verify(factory => factory.Create(), Times.Once); ``` In NSubstitute, you specify the expected number of times a method was called as part of `Received()`. Here is how to check that a method was called exactly once with NSubstitute: ```csharp _mock.Received(1).Create(); ``` ### Verify a call was never made You may want to ensure that a call was never made, such as with an exceptional case. This is how you ensure a call was never made using Moq: ```csharp _mock.Verify(factory => factory.Create(), Times.Never); ``` This is how you ensure a call was never made using NSubstitute: ```csharp _mock.Received(0).Create(); ``` ### Verify a call for a specific number of calls What if you have a method that needs to be called a specific number of times? You can test for an exact number of calls - such as 5 times - using Moq like this: ```csharp _mock.Verify(factory => factory.Create(), Times.Exactly(5)); ``` The way to test if a method was called 5 times in NSubstitute looks like this: ```csharp _mock.Received(5).Create(); ``` ### Verify no other calls If you want to verify that no other calls were made, you can do this in Moq: ```csharp _mock.VerifyNoOtherCalls(); ``` There is no direct equivalent to `VerifyNoOtherCalls()` in NSubstitute. However, some folks have suggested looking into assertions on the substitute's `ReceivedCalls()` results. ### Verify async calls If you need to verify that an asynchronous call was made, this is how you would do it in Moq: ```csharp _mock.Verify(client => client.GetAsync()); ``` When verifying asynchronous calls with NSubstitute, you need to make sure to use the `await` keyword, like this: ```csharp await _mock.Received().GetAsync(); ``` ## Setting up arguments in mocked method calls Setting up arguments is common when testing with mocked methods. With Moq, arguments can be specified with `It.Is()` and `It.IsAny()`, like this: ```csharp _mock.Setup(calc => calc.Add(It.IsAny())); _mock.Setup(calc => calc.Add(It.Is(num => num % 2 == 0)); ``` In NSubstitute, you use `Arg.Any()` and `Arg.Is()` to add arguments to a mocked method call, like this: ```csharp _mock.Add(Arg.Any()).Returns(5); _mock.Add(Arg.Is(num => num % 2 == 0)).Returns(5); ``` ## Accessing a mock's calls and arguments If you want to access the calls and arguments, you can do this with both packages. In Moq, calls are known as **invocations**. Arguments are tied to an invocation. The following code gets the arguments for the first invocation: ```csharp _mock.Invocations(); _mock.Invocations[0].Arguments; ``` In NSubstitute, calls are **received calls**. Arguments are tied to a call. The following code gets the arguments for the first call using NSubstitute: ```csharp _mock.ReceivedCalls(); _mock.ReceivedCalls().First().GetArguments(); ``` ## Setting up exceptions Testing isn't just about the happy path. This is how you handle testing with exceptions using Moq: ```csharp _mock.Setup(factory => factory.Create()).Throws(new Exception()); _mock.Create().Throws(new Exception()); ``` You can also test with exceptions using NSubstitute: ```csharp _mock.Setup(client => client.GetAsync()).ThrowsAsync(new Exception()); _mock.GetAsync().ThrowsAsync(new Exception()); ``` ## Conclusion These are just some of the many things that you can do in Moq and NSubstitute. If you are considering migrating from Moq to NSubstitute, we also recommend checking out [Ardalis' post on Porting Moq to NSubstitute](https://ardalis.com/porting-moq-nsubstitute/). If you have a project involving this that could use an extra set of hands on, [contact us](https://nimblepros.com/talk-to-us-1)!