The analysis of sentimental posts about software testing on Stack Overflow reveals that motivation and commitment of developers to use software testing methods is not only influenced by tools and technology. Rather, attitudes are also influenced by socio-technical factors. No prior studies have attempted to talk with Stack Overflow users about the sentimental posts that they write, yet, this is crucial to understand their experiences of which their post is only a fragment. As such, this study explores the precursors that make developers write sentimental posts about software testing on Stack Overflow. Through semi-structured interviews, we reconstruct the individual experiences of Stack Overflow users leading to sentimental posts about testing. We use the post as an anchor point to explore the events that lead to it and how users moved on in the meantime. Using strategies from socio-technical grounded theory (STGT), we derive hypotheses about the socio-technical factors that cause sentiment towards software testing.