Trigger and Data Acquisition (TDAQ) of the ATLAS experiment is a large distributed and heterogeneous system: it consists of thousands of interconnected computers and electronics devices that operate coherently to read out and select relevant physics data. Advanced testing and diagnostics capabilities of the TDAQ control system are a crucial feature which contributes significantly to smooth operation and fast recovery in case of problem and, finally, to the high efficiency of the whole experiment. The base layer of the verification and diagnostic functionality is a test management framework. We have developed a flexible test management system that allows experts to define and configure tests for different components, indicate follow-up actions to test failures and describe inter-dependencies between TDAQ or detector elements. This development is based on the experience gained with the previous test system that was used during the first three years of data taking. We discovered that more emphasis needed to be put on the flexibility and configurability of the verification and diagnostics functionality by the many people that are, each, knowledgeable and expert on individual components of the experiment. In this paper we describe the design and implementation of the test management system and also some aspects of its exploitation during the ATLAS data taking in the LHC Run 2.