All 15 API Versioning questions
More in API Versioning
What does the ReportApiVersions option do, and what response headers does it add? How do you implement URL segment-based API versioning for controllers using [ApiVersion] and route templates? How does header-based API versioning work, and what's a scenario where it's preferred over URL segment versioning? What is the difference between versioning at the API level (entire controller/group) versus versioning individual actions within a shared controller? How does query string-based API versioning work, and what are its trade-offs compared to URL segment versioning? How do you handle API versioning for gRPC services, given gRPC's contract is defined via .proto files rather than URL routes? How do you configure a sunset date for a deprecated API version so clients receive a clear removal timeline? How do you implement API versioning for minimal API endpoints, since they don't use controller attributes? How do you deprecate an API version gracefully, notifying consumers via response headers before eventually removing it? How does ASP.NET Core API versioning handle a request that doesn't specify any version at all?
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ASP.NET Core › API Versioning

How do you unit test that a specific API version's controller action behaves correctly, given the version-based routing?

Intermediate

Answer

Since versioned routing resolution happens at the ASP.NET Core routing/framework level (not inside your action method's logic), unit tests typically just instantiate and call the specific versioned controller class directly (e.g., ProductsV2Controller) without needing to simulate the actual HTTP routing/version-matching machinery -- reserving full routing verification (confirming a request with a given version header/URL actually reaches the intended controller) for integration tests using WebApplicationFactory.
[Fact]
public void GetAll_V2_ReturnsExpandedProductFields() {
    var controller = new ProductsV2Controller(_mockService.Object);
    var result = controller.GetAll() as OkObjectResult;
    var products = result.Value as List<ProductV2Dto>;
    Assert.Contains(products, p => p.Currency != null);  // v2-specific field
}
Real-world example A unit test suite directly tests ProductsV2Controller's business logic in isolation, while a separate integration test suite confirms that a request with 'api-version: 2.0' actually routes to that controller correctly -- keeping the two concerns cleanly separated.

Common follow-ups: What would an integration test verifying correct version routing look like?;How do you test the deprecation header behavior specifically?

Testing ASP.NET Core Applications;Controllers vs Minimal APIs
All 15 API Versioning questions