What type of defects is visual testing least likely to detect?

Visual testing primarily focuses on the appearance of the product, making it particularly effective for identifying aesthetic defects, layout issues, and color mismatches. These types of defects are easily spotted through visual inspection, as they pertain to how the product looks. Visual tests can quickly reveal inconsistencies in design, color accuracy, and overall aesthetics which are essential in ensuring the quality of the user interface or product presentation.

On the other hand, functional defects deal with how a product operates or performs its intended tasks. These defects often require more than visual inspection for detection, necessitating functional testing or automated testing techniques to evaluate the underlying operations and processes. Since visual testing doesn’t assess functionality, it is least likely to detect functional defects accurately. Thus, while visual testing is effective in recognizing visual and aesthetic discrepancies, it falls short regarding issues that affect performance and usability.