In this paper we introduce an algorithm to automatically encode an ASM specification in PROMELA, the language of the model checker Spin, and we present a method exploitingthe counter example generation feature of Spin, to automatically generate from ASM specifications test sequences which accomplish a desired coverage. ASMs are used as test oracles to predict the expected outputs of units under test. A prototype tool that implements the proposed method is also presented. Experimental results in evaluatingthe method are reported. The experiments include test sequence generation, tests execution, code coverage measurement for a case study implemented in Java, and comparison with random tests generation. Benefits and limitations in using model checkingare discussed.