Numerous researchers have suggested that there are multiple mathematical knowledge and skill areas needed by teachers in order for them to be effective teachers of mathematics: knowledge of the mathematics that are the goals of instruction, advanced mathematics beyond the instructional material, and mathematical knowledge that is specific to what is needed to teach students. The research reported here is about the development of a test of teachers' knowledge in these three areas related to the teaching of algebra. The test development process is described and the results of several analyses are reported that had the goal of checking whether valid inferences can be made about the hypothesized components of teacher knowledge.