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GoAWK's code coverage feature

GoAWK implements code coverage functionality, similar to the code coverage built into Go. This feature was implemented by Volodymyr Gubarkov (xonixx), primarily in PR #154.

Here is a screenshot using GoAWK's coverage feature on a simple AWK program (prog.awk):

Example code coverage screenshot

Basic usage

The simplest way to generate a coverage report is to run your AWK program with the -coverprofile option. To run the program in the default coverage mode and write the coverage report to cover.out, run the following:

$ goawk -f prog.awk -coverprofile cover.out
will always run
should run

This generates a file cover.out with coverage profile data for the execution of prog.awk.

We rely on the Go toolchain to visualize the coverage report, specifically the go tool cover command. This command renders a coverage report to HTML. If you don't have Go installed, install it now.

To write the HTML coverage report (like the one shown in the screenshot above) to a temporary file and open a web browser displaying it, run the following:

$ go tool cover -html=cover.out

To write the HTML file to a specified file instead of launching a web browser, use -o:

$ go tool cover -html=cover.out -o cover.html

If you want to see coverage-annotated source code, use the -d option in addition to -covermode. This might be useful for debugging, or to see how GoAWK's coverage feature works under the hood:

$ goawk -f prog.awk -covermode set -d
BEGIN {
    __COVER["3"] = 1
    print "will always run"
    if ((1 + 1) == 2) {
        __COVER["1"] = 1
        print "should run"
    } else {
        __COVER["2"] = 1
        print "won't run"
    }
}

All command-line options

  • -coverprofile fn: set the coverage report filename to fn. If this option is specified but -covermode is not, the coverage mode defaults to set.
  • -covermode mode: set the coverage mode to mode, which can be one of:
    • set: did each statement run?
    • count: how many times did each statement run? (produces a heat map report)
  • -coverappend: append to coverage profile instead of overwriting it. This allows you to accumulate coverage data across several different runs of the program.

Future work

  • Add a way to support per-function coverage reporting, similar to go tool cover -func=cover.out.
  • More complete handling for coverage of if/else (see details).

Feedback

Please open an issue if you have bug reports or feature requests for GoAWK's code coverage support.