---
url: https://jasperfx.github.io/alba/scenarios/problemdetails.md
description: >-
  Assert on RFC 9457 problem details and validation problem responses from
  ASP.NET Core in Alba scenarios.
---

# Problem Details

ASP.NET Core writes error responses in the [RFC 9457](https://www.rfc-editor.org/rfc/rfc9457) problem details
format from `Results.Problem()`, `Results.ValidationProblem()`, `[ApiController]` model validation and the exception
handler, and frameworks such as Wolverine do the same. Your application might too. Alba has assertions for these responses:

```cs
[Fact]
public async Task problem_details_members()
{
    await _host.Scenario(x =>
    {
        x.Post.Url("/withdrawals");
        x.ShouldReturnProblemDetails(409)
            .WithTitle("Insufficient funds")
            .WithDetail("The balance is 10.00")
            .WithType("https://example.com/problems/insufficient-funds")
            .WithExtension("balance", 10m)
            .WithExtension("limits", new[] { 5, 50 });
    });
}

[Fact]
public async Task validation_errors_by_field()
{
    await _host.Scenario(x =>
    {
        x.Post.Url("/deposits");
        x.ShouldReturnValidationProblem()
            .WithValidationError("Amount", "must be positive")
            .WithValidationError("amount", "two decimal places")
            .WithValidationError("Currency");
    });
}
```

snippet source | anchor

* `ShouldReturnProblemDetails(statusCode)` asserts the status code and the `application/problem+json` content type.
* `ShouldReturnValidationProblem()` also requires an `errors` member. The status code defaults to 400; pass another
  one, such as 422, if the application uses it.
* `WithTitle(...)`, `WithDetail(...)` and `WithType(...)` compare those members exactly.
* `WithExtension(name, value)` compares an extension member structurally, serializing the expected value with the
  application's JSON settings in the same way as [`JsonPath(...)`](json.md#asserting-on-json-structure).
* `WithValidationError(field)` asserts that a field has a validation error. Field names are matched without regard to
  case, because applications differ in how they case the keys. Pass a second argument to require that one of the
  field's messages contains that text.

All failures are reported together with the response body.