First of all to perform comprehensive test coverage is impossible unless the source code is very small and the time frame is large as stated by http://www.softwareqatest.com/ and many professionals in the IT industry.

Secondly should one decide to go for comprehensive test coverage then you must provide every possible test case secanrio imaginable and mind you these are not only to be software based but should be hardware based as well.For this gigantic task you must have the following at your disposle:

1.Good knowledge about use cases test cases test suites and the tools by which they can be developed.

2.Patience as when you get into the groove of testing there could be delays for your results and in case a bug is found then bug removal can be very tiring irritating and often frustrating especially when yo enter regression testing.

3.An attitude that follows your head not your gut/instincts.

4.A tracking policy that is well based and is supported by a tracking mechanism and personnel that keep a strict track of how the testing is being performed particulalry near deadlines.

The comprehensive test coverage as I get it is the coverage of testing according to the functional requirements technical design document use cases and any specific user requirement.

The testing of Hardware could be considered as the part of load testing.

To make sure that the test coverage as extensive we can prepare a tracebility matrix. This could be a simple excel having one column as the functional specification the next column could be the test case name and finally the last column could be the test script id.

After preperation of this document we can uniqely identify each requirement is matched to a test case and a test script.

This is the best way to track the test coverage. Though a tedious process but this process has certainly proved to be effective if followed properly.