This paper presents a rigorous testing and validation methodology for the EfficientVisionTransformer(EVT), a state-of-the-art deep learning model designed to predict vegetation indices from remotely sensed images in Southern Nigeria. Given the critical role of vegetation monitoring in ecological preservation and agricultural productivity, ensuring the accuracy and reliability of such models is paramount. The testing methodology uses a multi-pronged approach, including unit testing, integration testing, boundary value testing, and overall accuracy evaluation. Unit testing tested the correct operation of individual EVT components such as patch embedding, encoder, and decoder modules. Integration testing examined the flawless interoperability of various components, identifying any flaws in their interactions. Boundary value testing pushed the limits by evaluating the model's performance under extreme input situations, examining robustness and capacity to deal with edge cases. Importantly, accuracy testing using real-world data from Southern Nigeria demonstrated the EVT's prediction capabilities. The model has an amazing root mean square error of 0.04582. Furthermore, the normalized root mean square errors were 0.04582 when normalized to the 0-1 range and 0.00864 when normalized to the target variable's 1.8-7.1 range. These measurements show that the model is very accurate, with predictions departing from real vegetation index values by <1% of the whole data range on average. The extensive testing methodology established the EfficientVisionTransformeras a reliable and high-performing solution for predicting vegetation index in Southern Nigeria. The findings of this work provide major contributions to the advancement of remote sensing and deep learning research, as well as enabling more accurate vegetation monitoring, which is vital for ecological conservation, sustainable agriculture, and regional economic growth.