Exam ISO-9001-Lead-Auditor Topic 6 Question 14 Discussion

Scenario 1: AL-TAX is a company located in California which provides financial and accounting services.
The company manages the finances of 17 companies and now is seeking to expand their business even more The CEO of AL-TAX, Liam Durham, claims that the company seeks to provide top-notch services to their clients Recently, there were a number of new companies interested in the services provided by AL-TAX.
In order to fulfill the requirements of new clients and further improve quality, Liam discussed with other top management members the idea of implementing a quality management system (QMS) based on ISO 9001.
During the discussion, one of the members of the top management claimed that the size of the company was not large enough to implement a QMS. In addition, another member claimed that a QMS is not applicable for the industry in which AL TAX operates. However, as the majority of the members voted for implementing the QMS. Liam initiated the project.
Initially, Liam hired an experienced consultant to help AL-TAX with the implementation of the QMS. They started by planning and developing processes and methods for the establishment of a QMS based on ISO
9001. Furthermore, they ensured that the quality policy is appropriate to the purpose and context of AL TAX and communicated to all employees. In addition, they also tried to follow a process that enables the company to ensure that its processes are adequately resourced and managed, and that improvement opportunities are determined.
During the implementation process, Liam and the consultant focused on determining the factors that could hinder their processes from achieving the planned results and implemented some preventive actions in order to avoid potential nonconformities Six months after the implementation of the QMS. AL-TAX conducted an internal audit. The results of the internal audit revealed that the QMS was not fulfilling all requirements of ISO 9001. A serious issue was that the QMS was not fulfilling the requirements of clause 5.1.2 Customer focus and had also not ensured clear and open communication channels with suppliers.
Throughout the next three years, the company worked on improving its QMS through the PDCA cycle in the respective areas. To assess the effectiveness of the intended actions while causing minimal disruptions, they tested changes that need to be made on a smaller scale. After taking necessary actions, AL-TAX decided to apply for certification against ISO 9001.
Based on the scenario above, answer the following question:
As stated in scenario 1, AL-TAX tested the effectiveness of the intended actions as part of the QMS improvement through the PDCA cycle. Which stage did it perform in this case?