Perhaps Optym has the craziest interview process. There were two phone screens. They one hour interview with one of their systems engineers. The guy asked me about my experience and brought up questions on branch and bound algorithm, Bender's decomposition, and other methods/techniques. I then had one round of interview with one of the managers of the company. I think the objective was to understand if I am a good fit to the company's culture. Then they sent me a test! The test included GMAT problems, as well as OR problems. I took a look at the test and told them that I am withdrawing my application!! This is crazy! I am sure that there will be similar tests in the on-site interview!