Test.cs

public class Tests
{
    [Fact]
    public async Task Lookup_returns_mapped_result_when_response_is_successful()
    {
        var json = """
                   {
                     "year": 2026,
                     "make": "Ford",
                     "model": "F-150"
                   }
                   """;

        var handler = new StubHttpMessageHandler(_ =>
            new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new StringContent(json, Encoding.UTF8, "application/json")
            });

        var httpClient = new HttpClient(handler);
        var sut = new VinDecoder(httpClient);
        var result = await sut.Lookup("123456789");

        Assert.Equal(2026, result.Year);
        Assert.Equal("Ford", result.Make);
        Assert.Equal("F-150", result.Model);
    }
}