Using Spans
The span attribute allows you to control which coverage recordings are merged to form a current coverage report. By default, Clover only considers coverage recording files that were written after the last Clover compilation. In some situations you may want to include earlier coverage recordings. The span attribute lets you do this.
The span attribute takes an Interval which tells Clover how far back in time since the last Clover compilation that coverage recordings should be merged to build the report.