10.2 Manipulating code coverage data

Optionally you can manipulate code-coverage-data before displaying it, using the functions described in this section.

The code-coverage-data structure contains information about some set of files. Except for the internal code-coverage-data, this information does not change. The internal code-coverage-data object is updated whenever code that was compiled with code coverage runs. Also, when a binary file that was compiled with code coverage is loaded it adds itself to the internal code-coverage-data (overwriting any existing data associated with that file). Most of the functions for manipulating code-coverage-data can operate on the internal code-coverage-data structure by passing t as the data argument. See the specific functions for details.

The interface to code coverage data allows you to:

• Copy code-coverage-data, save it into a file, and load a code-coverage-data from a file.

  These functions are copy-code-coverage-data, copy-current-code-coverage, merge-code-coverage-data, filter-code-coverage-data, save-code-coverage-data, save-current-code-coverage and load-code-coverage-data.

• Add or subtract two code-coverage-data structures. This means add or subtract all the corresponding counters from the two structures. This is allowed only if all the files that are in both structures are from the same compilation.

  For example, you may subtract the data of one test from another to see how they differ in the way they use their code.

  These functions are add-code-coverage-data, destructive-add-code-coverage-data, subtract-code-coverage-data, destructive-subtract-code-coverage-data, reverse-subtract-code-coverage-data and destructive-reverse-subtract-code-coverage-data.

• Clear the internal code-coverage-data (this means eliminating the files from it) or reset it (this means setting the counters to 0), or setting to another code-coverage-data.

  These functions are clear-code-coverage, reset-code-coverage and restore-code-coverage-data.

• Set an internal snapshot, and later compare with it.

  These functions are set-code-coverage-snapshot, get-code-coverage-delta and reset-code-coverage-snapshot.

• Generate statistics about the contents of the code coverage, by code-coverage-data-generate-statistics.