Expectations for testing from agency developing emails
I'm currently a designer on a very small team in a corporate environment and because of my background and previous experience (at an agency) in email, am also the resident email expert and email developer. We've recently started using a new to us agency for a large campaign involving email and direct mail. They're developing the emails within our environment in Marketing Cloud Content Builder starting with our custom templates and content pieces. They've developed similar campaigns for other clients using other ESPs that have testing capabilites built in, Marketing Cloud does not. I use Litmus (of course) and find it essential.
My expectation of an agency developing emails is that they use Litmus or a similar service to test and solve email client issues before it comes to us to do our testing, final checks and sending. My question comes in that they want to charge us additional money to do this level of testing, my guess is to pay for the service but maybe also for the additional time. I feel it's a baseline part of the service they should provide to develop emails and should not cost extra -- or at least make that charge invisible to the client and don't make an issue of it.
We've gone through a full set of email development with them and it fell to me to do a lot of the testing which doesn't feel right when we're paying a lot of money to an agency to do it. This should have all been agreed upon in setting up the relationship and project initially but that obviously didn't happen.
I've been on both sides of this situation and would love to know your opinion. Am I expecting too much? What's standard in your experience?