With the increasing popularity of open-source version control platforms like GitHub, developers get more feedback on the changes they make. A common tool in version control systems is the highlighted difference view of the source code. This enables reviewers to quickly view the changes made. A missing feature is comparison of the test coverage. Since more and more projects develop a test suite to ensure quality, it is worth looking into how a change affects the test coverage of the project. In this thesis, a tool called Operias is proposed and implemented. Operias is a tool which accepts two versions of a project and calculates the difference in both source code and in statement coverage. The tool generates a HTML site, which developers can use to quickly review the changes. It is possible to run Operias as a service and to connect it to GitHub. This way, a report is automatically generated for every pull request that is opened. This helps reviewers to determine whether to accept the pull request or not. The main contributions of this thesis is the generic description of how the tool Operias works and the actual implementation of the tool. The tool is available on GitHub, and with the tool we conducted a real life evaluation with three open-source projects on GitHub to determine the usefulness of the tool. We found that in many cases Operias can help developers and reviewers during the review process.