I am a software developer who is creating integrations services between the ERP system of our customers and our system (dataflow happens via XML and webservices). I am doing this for around 4-5 years already and completed +10 integrations successfully. I am doing everything from planning to deployment and support although I am not the project leader. I am currently the only one having this experience at work. We are now moving to a new ERP system and have a lot of third parties involved in it. One of them are also specialized in general integrations but not specifically the part which I am doing. The integrations will be created by part of middleware solutions and mostly in the beginning by the third parties.
To cut the long story short. There is no overall design yet but the main objects are identified. On basis of this the high level planning is made. So what they are going to do is trying to recreate the workflow and data flow exactly the same as the old ERP system. But when this is built we also need to do an UAT with the customer. Normally this UAT takes 4 to 20 weeks (like 15 hours per week unless a major issue pops up) per country. They planned for me to do 4 countries now in 2 week and after 2 weeks they intend to go live. The customers aren't notified yet when we want to test with them.
Now I raised a discussion on this and tell them this is impossible. Now the project leader (newly graduated guy with 2 years exp who is on the side of the third parties) tells me that these 2 weeks is calculated as effective time, so i need to see it as 40/80 hours. But after 2 weeks on the planning there is a go live planned (move to production). He told me: don't mind, if UAT during that week is on pause, you can focus on another integration build instead. While those integrations builds all are (according to planning) be done before the UAT testing..
So when I am trying to make it a bit more realistic, the project leader + third parties are seeing me as a complicator.. And the tell me to be optimistic. How can I be optimistic + realistic in planning a good amount of time, and not make it more complicated and longer than expected? Or am I really making it to complex here?