Fix incorrect dotnet CLI command in NUnit tutorial

Co-authored-by: gewarren <[email protected]>

Author: Copilot

docs/core/testing/unit-testing-csharp-with-nunit.md

@@ -86,12 +86,15 @@ The [dotnet new](../tools/dotnet-new.md) command creates a test project that use
 > [!NOTE]
 > Prior to .NET 9, the generated code may reference older versions of the NUnit test framework. You may use [dotnet CLI](/nuget/consume-packages/install-use-packages-dotnet-cli) to update the packages. Alternatively, open the *PrimeService.Tests.csproj* file and replace the contents of the package references item group with the code above.
 
-The test project requires other packages to create and run unit tests. The `dotnet new` command in the previous step added the Microsoft test SDK, the NUnit test framework, and the NUnit test adapter. Now, add the `PrimeService` class library as another dependency to the project. Use the [`dotnet reference add`](../tools/dotnet-reference-add.md) command:
+The test project requires other packages to create and run unit tests. The `dotnet new` command in the previous step added the Microsoft test SDK, the NUnit test framework, and the NUnit test adapter. Now, add the `PrimeService` class library as another dependency to the project. Use the [`dotnet add reference`](../tools/dotnet-reference-add.md) command:
 
 ```dotnetcli
-dotnet reference add ../PrimeService/PrimeService.csproj
+dotnet add reference ../PrimeService/PrimeService.csproj
 ```
 
+> [!NOTE]
+> If you're using .NET 10 SDK or later, you can use the "noun first" form: `dotnet reference add ../PrimeService/PrimeService.csproj`.
+
 You can see the entire file in the [samples repository](https://github.com/dotnet/samples/blob/main/core/getting-started/unit-testing-using-nunit/PrimeService.Tests/PrimeService.Tests.csproj) on GitHub.
 
 The following outline shows the final solution layout: