A defect-tracking system (also known as bug tracking system, bug tracker, or issue tracker) is a software system that keeps track of reported software defects in software projects. The main benefits of this kind of systems is to provide a centralized overview of development management, bug reporting, and even feature request. It is also common to maintain a list of pending items, often called backlog.

There are a bunch of defect-tracking systems available, both proprietary and open source. In this section, we make a brief of several of the most well-known:

• JIRA (https://www.atlassian.com/software/jira): It is a proprietary defect-tracking system created by Atlasian. In addition to bug and issue tracking, it provides managements capabilities such as SCRUM and Kanban boards, a language to query issues (JIRA Query Language), integration with external systems (for example, GitHub, Bitbucket), and an add-ons mechanism to extend JIRA with plugins from the Atlasian Marketplace (https://marketplace.atlassian.com/).
• Bugzilla (https://www.bugzilla.org/): It is an open source web-based, defect-tracking system developed by the Mozilla Foundation. Among its features, we can find a database designed to improve performance and scalability, query mechanism for searching defects, integrated e-mail capabilities, and user roles management.
• Redmine (http://www.redmine.org/): It is an open source, web-based defect-tracking system. It provides wikis, forums, time tracking, role-based access control, or Gantt charts for project management.
• MantisBT (https://www.mantisbt.org/): It is another open source, web-based defect tracking system designed to be simple but effective. Among its features, we can highlight its event-driven plugin system to allows extensions both official that third-party, multi-channel notification system (e-mail, RSS feed, Twitter plugin, and so on), or role-based access control.
• GitHub issues (https://guides.github.com/features/issues/): It is the tracking system integrated in each GitHub repository. The approach of GitHub issues is to provide a generic tracking system for defects, task scheduling, discussions, and even feature request using GitHub issues. Each issue can be categorized using a customizable label system, participators management, and notifications.