With the spread of smartphones, the importance of automated testing of mobile applications has increased. However, many current approaches are inadequate, as they are not able to test functions that are available only on hard-to-reach GUI, which is a screen that can be reached only through a specific sequence of input events. To solve this problem, there has been an increase in testing research based on reinforcement learning, specifically Q-learning. Each research uses different learning targets and reward function. Testing research has also been done using Deep Q-Network, which extends reinforcement learning in a “deep” way. Although each work has conducted their own evaluation, it is not clear how the combination of learning algorithm, learning target, and reward function affects the result. To bridge this gap, we have conducted an empirical study comparing eight possible combinations. Our study found that the combination of Deep Q-Network as the learning algorithm, component as the learning target, and GUI change ratio as the reward function had the highest test quality in terms of code coverage.