Test coverage matrix is a checklist which ensures that the functionality of the given screen(unit) is checked in all possible combinations (positive and negative) which have not been covered in test cases. Test coverage matrix is usually prepared for a screen having large number of controls (textboxes, dropdowns, buttons etc) usually, test coverage matrix is prepared in a spread sheet having all the controls (textboxes, dropdowns, buttons etc) in the columns and then all possible entries in those fields in the rows with an ''yes'' or ''no'' in the rows against the controls listed in the columns. For example, consider a ''login'' screen wherein we have ''username'' and ''password" textfields.
While preparing test coverage matrix, the first column will be ''s.no'' and the second will be ''username" and ''password" will be the third field followed by ''ok'' and ''cancel'' button. Then, in the first row for s.no 1, enter ''yes'' for both ''user name'' and ''password'' columns, ''yes'' implying that a value is entered in that field. In the second row, enter ''yes'' and ''no'' and in the third row, ''no'' and 'yes'' and so on.
The complexity increases with the number of controls in the screen. Each of the row is considered as one condition and executed while testing. This is how we prepare test coverage matrix. (this is a black box testing technique).
While, Traceability matrix serves in mapping the test cases to the requirements. It serves as a checklist wherein all the requirements (of srs) are listed and the test cases covering the corresponding requirement is listed against each requirement. Every company may have their own template for rtm, but they serve the same purpose as described above.