Analytical methods to perform CU testing should ideally be fast, noninvasive and achieved with limited sample preparation. Recently, transmission near-infrared (NIR) spectroscopy and transmission Raman spectroscopy have both been explored as alternative methods for rapid and non-destructive on- and at-line CU testing with no sample preparation. Although quick and nondestructive, transmission NIR spectroscopy suffers from poor chemical selectivity and is sensitive to changes in the testing environment. Transmission Raman spectroscopy combined with chemometric modeling is quickly emerging as a valued technique for CU testing due to its high chemical specificity, which is particularly useful when dealing with complex pharmaceutical formulations that contain multiple components.