We design and validate simulators for generating queries and relevance judgments for retrieval system evaluation. We develop a simulation framework that incorporates existing and new simulation strategies. To validate a simulator, we assess whether evaluation using its output data ranks retrieval systems in the same way as evaluation using real-world data. The real-world data is obtained using logged commercial searches and associated purchase decisions. While no simulator reproduces an ideal ranking, there is a large variation in simulator performance that allows us to distinguish those that are better suited to creating artificial testbeds for retrieval experiments. Incorporating knowledge about document structure in the query generation process helps create more realistic simulators.