Hi @pibu,
Welcome to the community 
I was able to reproduce the issue by using the tests from OpenZeppelin Upgrades: Step by Step Tutorial for Truffle and converting to OpenZeppelin Test Environment: https://docs.openzeppelin.com/test-environment/0.1/migrating-from-truffle
I will need to come back to you whether testing with OpenZeppelin Test Environment is supported or if we need to use Truffle Test when using Upgrades Plugins.