Validating language tests has not yet received sufficient attention from researchers and language teaching professionals. Adopting validity frameworks guarantees more valid and reliable tests with systematic decisions. It is insufficient considering just the test design and test setters; there is a need to consider the cognitive process that second language learners undergo to comprehend a test task. Therefore, this study attempts to validate ESP test in order to examine its potential and shortcomings in assessing engineering students’ English ability. To achieve this, Weir’s socio-cognitive framework for validating reading tests (2005) was adopted throughout the study. It is instructive and comprehensive in nature. It has five components that ensure meaningful and typical test validity process in all test stages which include a ‘priori’, during and a ‘posteriori’ of the test event. The study involves three phases: a validation study on the Existing ESP Test, the validation of a Sample Proposed ESP Test and a comparative validity report of the two tests. This study may be beneficial for test instructors, professionals and researchers who are interested in educational tests.