public async Task PostsToTheCorrectUrl()
{
var connection = Substitute.For <IApiConnection>();
var client = new ProductsClient(connection);
await client.AddFollower(123, 1234);
Received.InOrder(async() =>
{
await connection.Post <ProductFollower>(Arg.Is <Uri>(u => u.ToString() == "products/123/followers"),
Arg.Is <object>(o => o.ToString() == new { user_id = 1234 }.ToString()));
});
}