Background and Context: Productive failure (PF) is a learning paradigm that flips the order of instruction: students work on a problem, then receive a lesson. PF increases learning, but less is known about student emotions and collaboration during PF, particularly in a computer science context. Objective: To provide insight on students' emotions and reasoning during PF activities and their relation to performance. Method: We conducted a PF study (N = 48) with a programming problem. We used a mixed-methods approach to analyze students' emotions, reasoning, and pretest/posttest performance. Findings: Uncertainty occurred frequently compared to confusion, frustration, and positive affect. The constructive contributions made during problem solving correlated positively with posttest scores. Implications: Although students failed to produce a correct solution, there were few instances of frustration and a promising amount of constructive reasoning during collaboration. This, coupled with prior work showing that PF improves learning over standard instruction, indicates that PF is a promising approach for computer science education.