An example of writing test for APIs in Asp.Net Core with xUnit
[Fact]
public async Task When_IdIsNotValid_Then_NotFoundStatusCodeShouldBeReturned()
{
var httpClient = _factory.CreateClient();
var userResponse = await httpClient.GetAsync($"/api/users/{-1}");
userResponse.StatusCode.Should().Be(HttpStatusCode.NotFound);
}