The present disclosure describes devices and techniques for testing. In particular, the disclosure describes testing systems that are portable and easy to operate. The testing system can include a measurement apparatus that can be used to measure spectral characteristics of a sample and can be in a portable, hand-held form-factor. The testing system also includes a computing device, such as a mobile phone, a laptop, or a personal computer that can communicate with the measurement device over a wired or a wireless communication link and also can have form-factors that are portable. The computing device can run applications or programs that receive spectral data of the sample from the measurement apparatus and can process the received spectral data to determine various properties of the sample. As both the measurement apparatus and the computing device are portable, the measurements can be easily made at site where the fluid is produced.