The development of proficiency in the practices used by scientists and engineers is considered an important student outcome of laboratory instruction. We developed tasks to assess students' use and development of selected scientific and engineering practices in the general chemistry laboratory using an adapted evidence-centered design approach. In this paper, we provide a detailed description of the process of development and validation of these assessment tasks, using one of our tasks to illustrate the process. The tasks show strong evidence of validity and reliability for revealing students' understanding of scientific and engineering practices within the research context.