Being able to monitor how quality evolves is a good start (see Historical Information).
The next step would be to manage your technical debt on your current developments in order to keep it under control.
To deal with that, a Differential Services is provided on measures, issues and coverage by unit tests on new code.
To activate this service, pick the desired period in the Time changes... drop down list:
When a period is selected, the differential values will appear next to the project measures:
This service will help you focus your effort of quality on current developments:
To determine the creation date of an issue, during each analysis, the following algorithm is executed to determine if an issue is new or existed previously. For each issue, three of four criteria (rule; line number; line content or "hash"; and message) must match for a detected issue to be matched up with an existing one:
In any other case, the issue is a new one.
Three reasons can explain this:
When activating the SCM Activity Plugin, you will be able to separate coverage by unit tests of new code from old (based upon a given cut-off date) in order to track the new code which does not have any/enough unit tests.
A live example is available on Nemo.
Three periods can be configured globally and will be available and common to all projects. Go to Settings > General Settings > General > Differential Views to set these properties.
Two additional periods can be configured and be specific to the current project. Select your project and go to Settings > General > Differential Views to set these properties