Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchPC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11To test FizzBuzz in an ASP.NET Core application, keep the rule in a plain C# method, cover that method with xUnit unit tests, and add a small integration test that calls the HTTP endpoint through WebApplicationFactory<Program>. Separating the two layers means an arithmetic mistake and a routing or hosting mistake fail in different tests, which makes the cause obvious.
Define the contract before writing tests
ASP.NET Core does not define what FizzBuzz returns. The rules below are the conventional teaching contract, and this tutorial adopts them as its own choice:
As an Amazon Associate I earn from qualifying purchases.
| Input | Result | Rule |
|---|---|---|
| 1, 2, 7 | The number as text | Not divisible by 3 or 5 |
| 3, 9 | Fizz |
Divisible by 3 only |
| 5, 10 | Buzz |
Divisible by 5 only |
| 15, 30 | FizzBuzz |
Divisible by both 3 and 5 |
| 0, -3 | An ArgumentOutOfRangeException |
Outside the chosen domain of 1 and above |
The invalid-input row is a decision, not a requirement. Some implementations return an error string, others clamp the input, and the endpoint can translate the exception into a 400 response. Whatever you choose, write it down and test it, because the tests become the specification.
Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsSet up the projects
The web application and the test project should target the same framework. The Microsoft Learn page on integration tests in ASP.NET Core that this article relies on is written for ASP.NET Core 10.0, so the steps below use net10.0. If you target a different framework, check the matching version of the testing package before copying the commands.
#1 Best Overall
- Create the web application with the empty minimal template:
dotnet new web -f net10.0 -n FizzBuzzApp - Create an xUnit test project next to it:
dotnet new xunit -f net10.0 -n FizzBuzzApp.Tests - Reference the web project from the test project:
dotnet add FizzBuzzApp.Tests/FizzBuzzApp.Tests.csproj reference FizzBuzzApp/FizzBuzzApp.csproj - Add the integration-testing package. Use the 10.0 major version so it matches the framework:
dotnet add FizzBuzzApp.Tests/FizzBuzzApp.Tests.csproj package Microsoft.AspNetCore.Mvc.Testing --version 10.0.* - Open
FizzBuzzApp.Tests.csprojand confirm it contains<TargetFramework>net10.0</TargetFramework>. If the template chose another value, change it to match the web project.
Write the FizzBuzz logic as ordinary code
The rule does not need ASP.NET Core. Put it in a static class with no web types, so it can be tested directly and reused from any caller.
namespace FizzBuzzApp;
public static class FizzBuzz
{
public static string Convert(int number)
{
if (number < 1)
throw new ArgumentOutOfRangeException(nameof(number), "Must be 1 or greater.");
if (number % 15 == 0) return "FizzBuzz";
if (number % 3 == 0) return "Fizz";
if (number % 5 == 0) return "Buzz";
return number.ToString();
}
}Checking for 15 before 3 and 5 is what makes the combined case work. If the order is reversed, 15 returns Fizz and the tests below will catch it.
Rank #2
Unit tests for the transformation
Microsoft’s guidance on integration tests states the division of labour directly: “Use unit tests for routine tests of method logic that interact with these components.” Here the method under test is FizzBuzz.Convert, so every rule case belongs in a unit test. These tests create no host and run in milliseconds.
Free tools Windows power users keep installed
One-click scans. No signup required.
using FizzBuzzApp;
using Xunit;
public class FizzBuzzTests
{
[Theory]
[InlineData(1, "1")]
[InlineData(2, "2")]
[InlineData(7, "7")]
public void ReturnsNumberWhenNotDivisibleByThreeOrFive(int input, string expected)
=> Assert.Equal(expected, FizzBuzz.Convert(input));
[Theory]
[InlineData(3, "Fizz")]
[InlineData(9, "Fizz")]
public void ReturnsFizzForMultiplesOfThree(int input, string expected)
=> Assert.Equal(expected, FizzBuzz.Convert(input));
[Theory]
[InlineData(5, "Buzz")]
[InlineData(10, "Buzz")]
public void ReturnsBuzzForMultiplesOfFive(int input, string expected)
=> Assert.Equal(expected, FizzBuzz.Convert(input));
[Theory]
[InlineData(15, "FizzBuzz")]
[InlineData(30, "FizzBuzz")]
public void ReturnsFizzBuzzForMultiplesOfBoth(int input, string expected)
=> Assert.Equal(expected, FizzBuzz.Convert(input));
[Theory]
[InlineData(0)]
[InlineData(-3)]
public void ThrowsForInputBelowOne(int input)
=> Assert.Throws<ArgumentOutOfRangeException>(() => FizzBuzz.Convert(input));
}Two optional additions are useful. A sequence test can compare the output for 1 through 100 with an expected list, which catches ordering mistakes that single values miss. The length of that list is a choice of this tutorial, not a property ASP.NET Core requires. A second option is a check that the method never returns null or an empty string for valid input.
Integration test for the HTTP endpoint
An integration test earns its place when something other than the arithmetic can break: the route, the parameter binding, the status code, or the response format. Add a route to the web project. Because this project uses top-level statements, the generated Program class is internal, so the test project cannot see it until you make it public.
using FizzBuzzApp;
var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();
app.MapGet("/fizzbuzz/{n:int}", (int n) =>
{
if (n < 1)
return Results.BadRequest("Number must be 1 or greater.");
return Results.Text(FizzBuzz.Convert(n));
});
app.Run();
public partial class Program { }The test host starts the application in memory, so no port is opened. The test below checks the web boundary, not every arithmetic case:
using System.Net;
using Microsoft.AspNetCore.Mvc.Testing;
using Xunit;
public class FizzBuzzEndpointTests : IClassFixture<WebApplicationFactory<Program>>
{
private readonly HttpClient _client;
public FizzBuzzEndpointTests(WebApplicationFactory<Program> factory)
{
_client = factory.CreateClient();
}
[Fact]
public async Task GetFizzBuzz_ReturnsOkWithFizzBuzzForFifteen()
{
var response = await _client.GetAsync("/fizzbuzz/15");
Assert.Equal(HttpStatusCode.OK, response.StatusCode);
Assert.Equal("FizzBuzz", await response.Content.ReadAsStringAsync());
}
[Fact]
public async Task GetFizzBuzz_ReturnsBadRequestForZero()
{
var response = await _client.GetAsync("/fizzbuzz/0");
Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);
}
}The first test confirms that the route, binding, and text response work together. The second confirms that the boundary rule is enforced at the HTTP layer, where it turns into a status code. Neither test repeats the Fizz, Buzz, or number cases.
Run the tests and read the results
From the solution folder, run:
dotnet test FizzBuzzApp.Tests/FizzBuzzApp.Tests.csprojA successful run ends with a summary line beginning Passed! and reports zero failures. xUnit lists each [InlineData] row as its own test, so a failure names the exact input that broke.
Best Value
- Applying all key ASP.NET Core components, including MVC for HTML generation, .NET Core, EF Core, ASP.NET Identity, dependency injection, and more
- Integrating ASP.NET Core with leading client-side frameworks, including Bootstrap
- ASP.NET Core code for implementing business logic and data transformations
- Handling configuration, routing, controllers, views, and common tasks (including posting forms and presenting data)
- Performing complementary tasks: error handling, logging, application design, authentication, localization, and more
Failure modes to recognise
- A 404 for a non-numeric path such as
/fizzbuzz/abc: the:introute constraint rejects the request before your code runs. This is expected behaviour, so assert it only if you want to lock it in. - A 500 instead of a 400 for zero or negative input: the exception was not translated. Keep the explicit check in the endpoint, as shown above, rather than letting the exception escape.
- Restore or build errors in the test project: the test project and web project target different frameworks, or the
Microsoft.AspNetCore.Mvc.Testingversion does not match the framework. Align both tonet10.0and the 10.0 package line. - An error that
WebApplicationFactory<Program>cannot findProgram: thepublic partial class Program { }declaration is missing, or the application uses a namespace or a different entry-point type.
Further reading
For a broader walkthrough of C# testing, the O’Reilly book Practical Test-Driven Development using C# 7 includes xUnit and FizzBuzz exercises in its contents. It is not an ASP.NET Core FizzBuzz manual, so treat it as general background. Microsoft’s integration-testing guide for ASP.NET Core remains the primary reference for the test host setup.
The Bottom Line
Test the FizzBuzz rule with xUnit unit tests against a plain static method, then add one integration test per concern at the HTTP boundary. Keep the arithmetic in the unit tests and the routing, status codes, and response format in the endpoint tests.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →
