RASAT is a 3-axis stabilized earth observation satellite to be launched to a sun-synchronous LEO (Low Earth Orbit ) orbit. The primary design of attitude determination and control system (ADCS) flight software is performed by utilizing combination of MATLAB® and C environments. MATLAB environment ensures an easy design and test platform for quick algorithm simulation. After MATLAB simulations are performed successfully, the same algorithms are coded in C language to obtain the source code for the flight software. In the further development stage, Dynamic Attitude Simulator Environment (DASE) is used for simulating the real data to run the flight code in onboard computer. DASE software simulates the attitude and the orbit dynamics of the satellite and generates the corresponding sensor and actuator signals by using the satellite data bus as if they were received from the real sensors and sent to real actuators. Thus, DASE provides a suitable environment necessary to test and verify controllers and estimators as it simulates the satellite dynamics well before the launch. In this work, various aspects of ADCS flight code testing are considered and presented, such as sensor processing issues and actuator limitations. The success in realizing RASAT's operational phases are demonstrated by comparing the DASE-results with the desired behavior of RASAT in space. Two fundamental operational scenarios are presented as the result of simulations: 1) satellite de-tumbling after launcher separation and 2) 3-axis nadir pointing control.