All 15 Global Exception Handling & Middleware questions
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How do you handle exceptions specifically within minimal API endpoints, given they don't use the traditional MVC exception filter pipeline? What is the difference between handling exceptions with middleware versus using try/catch blocks directly in controller actions? How should a global exception handler differentiate between exceptions that should return specific client-facing details versus exceptions that should always show a generic message? What is the role of the [ApiController] attribute in automatically handling certain error scenarios without explicit exception handling code? What is ProblemDetails (RFC 7807/9457), and how does ASP.NET Core support it for standardized error responses? What information should be excluded from error responses in production to avoid leaking sensitive implementation details? How would you implement custom middleware to catch and log unhandled exceptions before they reach the exception handler, adding request-specific context? How does exception handling middleware interact with model validation errors in ASP.NET Core, and how do they typically produce different error response paths? How do you handle exceptions that occur during response streaming, after the response has already partially started sending to the client? How would you design exception handling middleware to support internationalized (localized) error messages returned to clients in different languages?
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How do you write an integration test verifying that your global exception handler produces the correct error response shape?

Intermediate

Answer

Using WebApplicationFactory<T> to spin up an in-memory test server, you can create a test-only endpoint or use an existing one that deliberately throws a known exception, then assert on the actual HTTP response's status code and JSON body shape returned by the real exception handling middleware -- verifying the full pipeline behavior rather than just unit testing the handler class in isolation.
public class ExceptionHandlingTests : IClassFixture<WebApplicationFactory<Program>> {
    [Fact]
    public async Task NotFoundException_Returns404WithProblemDetails() {
        var client = _factory.CreateClient();
        var response = await client.GetAsync("/api/products/99999");
        Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
        var problem = await response.Content.ReadFromJsonAsync<ProblemDetails>();
        Assert.Equal("Resource not found", problem.Title);
    }
}
Real-world example A team adds an integration test suite specifically verifying error response shapes for each custom exception type, catching a regression where a refactor accidentally changed the JSON field name from 'title' to 'Title', breaking client-side error parsing.

Common follow-ups: How does WebApplicationFactory differ from a full end-to-end test against a real deployed instance?;What's the value of testing the actual pipeline versus just unit testing the handler class directly?

Testing in .NET (xUnit Integration & Unit Testing);Global Exception Handling & Middleware
All 15 Global Exception Handling & Middleware questions