From 2011 to 2013, I accidentally studied US and Canadian teacher perceptions of standardized testing and its effects in the classroom. I had intended to study the role of equity issues in teacher practice; however, in conversation with teachers during initial semi-structured interviews in the United States, it became clear that understanding the impact of testing was a necessary prerequisite for understanding questions of equity in teacher practice and teachers’ work. The study was thus born somewhat unintentionally, and is the first mixed-methods study of the impacts of standardized testing on teaching in the United States and Canada. While standardized testing in the United States has been widely researched, its impact on teacher practice and professional identity has been largely overlooked. In the Canadian context, there is limited scholarship on standardized testing generally, and a paucity of research on the implications of standardized testing for teaching in particular. Although this research project included interview and survey research methods, this case study focuses on the evolution of the qualitative research outlined above, as well on as the ways in which early qualitative findings informed the development of the survey instrument. Although survey results produced and supported many key findings, semi-structured interviews with teachers offered unique insights into the daily professional life and work of teachers in an era of standardized testing. This case study sheds light on the opportunities and challenges that arise in qualitative research design, collection, and analysis, including questions of adaptability and flexibility, reliability and generalizability, and variation across research sites and populations.