In this paper, we present a new test data compression method for intellectual property (IP) cores testing, based on the reuse of parts of dictionary entries. Two approaches are investigated: the static and the dynamic. In the static approach, the content of the dictionary is constant during the testing of a core, while in the dynamic approach the testing of a core consists of several test sessions and the content of the dictionary is different during each test session. The efficiency of the proposed method is supported with extensive simulation results and comparisons to already known test data compression methods suitable for IP cores testing.