Using Bazel to generate coverage report

Question

I am using genhtml command to generate html coverage report from Bazel generated coverage.dat file:

genhtml bazel-testlogs/path/to/TestTarget/coverage.dat --output-directory coverage

The problem with using genhtml is that I have to provide the paths to the coverage.dat files (which are generated in bazel-testlogs/..) Is it possible to fetch those coverage.dat files as an output from another rule?

I would like to not have to call genthml command directly, but have Bazel handle everything.

Hi, Have you ever met `ERROR: output '_coverage/_coverage_report.dat' was not created` when run `bazel coverage` — stamaimer, Feb 26 '20 at 04:02
@stamaimer Do not recall this particular error, this was a while ago... — Zeitgeist, Feb 26 '20 at 16:49

Zeitgeist · Accepted Answer · 2017-10-04T19:06:14.480

12

I was not able to find a way to get coverage.dat files as an output of a bazel rule. However, I was able to wrap all the locations of all the .dat files as srcs to a filegroup in WORKSPACE directory:

filegroup(
    name = "coverage_files",
    srcs = glob(["bazel-out/**/coverage.dat"]),
)

and then use that filegroup in a custom .bzl rule that wraps the genthml command to generate html coverage report. So now I only have to call

bazel coverage //path/... --instrumentation_filter=/path[/:]

command to generate the coverage.dat files, generate html report and zip it up. Thus, bazel handles everything.

edited Oct 04 '17 at 19:06

answered Oct 02 '17 at 14:03

Zeitgeist

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Can you show how you used the `filegroup` and `genhtml` in combination to generate the final `index.html` coverage report? Did you use `genrule`? I added both `filegroup` and `genrule` in `BUILD` file in the root directory of my workspace but nothing seems to work. – Pavan Manjunath Aug 12 '18 at 23:48
@PavanManjunath not able to find all the code. I do have a custom .bzl file that uses run_shell with cmd to run python ```coverage html``` command, which generates the html file. Not sure if this is helpful, let me know if you need more info. – Zeitgeist Jan 02 '19 at 16:52
@Zeitgeist i don't understand, you can't post the code? or you can't find it? can you please share how you generate the HTML? – Sam Gammon Feb 17 '20 at 21:42
@sgammon Correct, I do not have access to the code, have been on a different project for years. To generate HTML file, I downloaded `genhtml` executable using `http_file()` in WORKSPACE, and then I created a custom bzl rule in which I incorporated a cmd command that runs that executable. (Being this was done so long ago, there are probably better ways to do things now) – Zeitgeist Feb 19 '20 at 18:21

score 3 · Answer 2 · edited Aug 07 '23 at 20:30

3

Bazel added support for C++ coverage (though I couldn't find much documentation for it).

I was able to generate a combined coverage.dat file with

bazel coverage -s \
  --instrument_test_targets \
  --experimental_cc_coverage \
  --combined_report=lcov \
  --coverage_report_generator=@bazel_tools//tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator:Main \
  //...

The coverage file gets added to bazel-out/_coverage/_coverage_report.dat

edited Aug 07 '23 at 20:30

Eponymous

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answered Dec 22 '18 at 23:40

Ryan Burn

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Which bazel version are you using? – pylipp Jan 17 '19 at 17:12
I tested with version 0.21.0 – Ryan Burn Jan 17 '19 at 20:32
FWIW, your link is dead – Taekahn Aug 31 '20 at 15:50

score 0 · Answer 3 · answered Jan 14 '22 at 14:34

For Java based project we can get code coverage in following way

To get coverage for complete module ->

Running coverage for complete project module. Run following command ->

bazel coverage ... --compilation_mode=dbg --subcommands --announce_rc --verbose_failures --jobs=auto  --sandbox_debug --build_runfile_links --combined_report=lcov --coverage_report_generator=@bazel_tools//tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator:Main

Then run following command from parent project directory to get html view. Html report is generated in output-directory-name we specified. From that open index.html to see coverage report.

genhtml -o <output-directory-name> bazel-out/_coverage/_coverage_report.dat

bazel-out directory usually gets created in project parent directory(e.g. where bazel WORKSPACE file is present)

To get coverage for specific IT/Test in a module ->

Running coverage for for specific IT/Test in a module. Run following command from project/sub-project directory ->

bazel coverage <class-name-of-Test-or-IT> --compilation_mode=dbg --subcommands --announce_rc --verbose_failures --jobs=auto  --sandbox_debug --build_runfile_links --combined_report=lcov --coverage_report_generator=@bazel_tools//tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator:Main

Then run following command from parent project directory to get html view. Html report is generated in output-directory-name we specified. From that open index.html to see coverage report.

genhtml -o <output-directory-name> bazel-out/_coverage/_coverage_report.dat

Using Bazel to generate coverage report

3 Answers3

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