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Code Coverage for Golang based applications

Code Coverage for Golang based applications

Integrate RKTracer runtime library Golang

Add RKTracer runtime library rk4go to the GOROOT, i.e., go installation folder. It’s a one-time setup. 

Windows or Linux:

To Integrate RKTracer runtime library source file to Golang installation. You can follow the following instructions.

Step 1: Open a command prompt and run the command. 

go env GOROOT

If Golang is in the path, then you should see the following output. In my case, it’s in path “/usr/lib/go-1.13”


Step 2: The command output gives us the path where Golang is installed and now create rk4go in src Golang installation folder and copy rk4go from the RKTracer installation folder to rk4go folder.

sudo cp  /home/username/share/rktracer/rk4go.go /usr/lib/go-1.13/src/rk4go/

Code Coverage for Golang-based applications using the RKTracer tool

Identify the project folder that needs to be instrumented and generate coverage data. Please make sure the project is configured and you’re able to test it.

Step 1: Enable RKTracer Tool

Then execute the following command to Turn ON (instrument)  or Turn OFF (un-instrument) RKTracer tool will instrument all Golang source files in a folder recursively.

RKTracer Turn ON/OFF commands 

  • rktracer -on  path-toproject/module/ go  -v
  • rktracer -off  path-toproject/module/ go  -v

“go” at the end means rktracer needs to only instrument python source files.

“-v”  at the end means rktracer needs show verbose instrumentation log.

The above command will instrument all the Golang source files in the project folder recursively. 

 Rebuild the application with commands go clean and go build commands.

Step 2: Install and test the instrumented application.

It might be Unit-testing or Functional testing, or Integration testing.

Once the testing is completed, you should see the file “rk-coverage.txt file.” now copy this file to the project folder or the path where you have executed the command “rktracer -on path-toproject/module/ go  -v” to instrument the project folder using the RKTracer tool. You should also see the “rktracer” folder with rktracer tool intermediate files. The “rktracer” folder will get generated at the time of the instrumentation. You need to copy the rk-coverage.txt file parallel to the rktracer folder in the project.

Coverage data file not found after testing.

RKTracer tool uses the following approaches to save coverage data.

  • Run unit/functional testing, and at the end RKTracer tool will automatically save coverage data on the host/server machine, that is, write coverage data to the rk-coverage.txt file.
  • Send a signal to the application running in an infinite loop to trigger and save coverage data. 
  • The application under test has crashed in the middle of testing on the host or target device. RKTracer saves coverage data to rk-coverage.txt and generate reports to check the point of a crash in reports.
  • Embedded devices without a file system or not connected to host while testing. In this case, rktracer RAW mode comes in to picture. You need to save the coverage data from the RKTracer variable. 

Suppose you cannot find the rk-coverage.txt file in the project working folder or target server machine. An application under test has not exited with the proper exit handler, i.e., atexit() handler, or your application might be running in an infinite loop. You can use the following two methods to save coverage data from memory to the file system.

Save coverage data when a particular function is executed at runtime testing.

Identify a function/method name in your application (ensure this function/method is not excluded from RKTracer instrumentation or file with this function). Then copy the function name and edit the rktracer.config in the RKTracer installation folder. 

For Golang programming language:  Add a new line at the end of rktracer.config file with “go-function-writeout” and function name. Here the function name is case sensitive, and you should also add empty braces, i.e., () at the end of a function name. In case if you have a function with an input parameter, it should still be empty braces. You can add multiple function names with one space to the list, as shown below.

  • go-function-writeout main()
  • go-function-writeout main()  OnCreate() fun()


After adding function name to rktracer.config file. You need to rebuild the application to re-instrument using rktracer. Coverage data will be saved to the rk-coverage.txt file when this function executes at runtime testing. 

Send a signal to save coverage data.

We can send a signal to the application running in an infinite loop to save coverage data to rk-coverage.txt.

  • Windows: send a kill signal using keys in the keyboard, i.e., Control+Pause/break. Contact support if you would like to add additional signal command to save coverage data at runtime testing.
  • Linux/Unix: Send a SIGWINCH signal: killall -SIGWINCH a.out or kill -SIGWINCH Process ID number. 

Step 3:Generate Code Coverage Reports

Once you have the rk-coverage.txt file, you need to run the “rkresults” command to generate HTML reports. Ensure that you run the “rkresults” command in the application root folder or where you have the “rktracer” folder generated at the time of build/Instrumentation.

rkresults command will search coverage data file “rk-coverage.txt” and map with JSON files (generated during instrumentation) in the rktracer folder and generate the HTML reports. You can manually open the HTML report using index.html.

After generating code coverage, make sure to turn off(un-instrument) the RKTracer tool for the application that we instrument to create reports.

rktracer -off  path-toproject/module/ go  -v

Generate code coverage for selected functions/files/folder

Generate coverage reports  for the selected folders






Suppose you need code coverage for source files from three different folders, i.e., core, keys, power, and ignore coverage for folders firmware_loader and lockdown. Edit rktracer.config in the RKTracer installation folder and go to the end of the file add the following information. 

ignore *.go

instrument */power/* */core/* */keys/*

never */firmware_loader/* */lockdown/*

ignore *.go = Ignores all golang source files from instrumentation

Instrument = Instrument source files from given folders

never = ignore selected folder  

Generate coverage reports only for selected functions from three different files.

fun_X() in source-file-X 

fun_Y() in source-file-Y

fun_Z() in source-file-Z

Suppose you need code coverage for selected functions from three different files. Edit rktracer.config in the RKTracer installation folder and go to the end of the file and set the following variables as shown below.  

ignore *.go

instrument *source-file-X.go *source-file-Y.go *source-file-Z.go

function-ignore *

function-instrument fun_X() fun_Y() fun_Z()

ignore *.go = Ignore all golang programming source files

instrument *file-X.go *file-Y.go *file-Z.go   = Instrument only these three source files.

function-ignore * = Then ignore all functions in the above three files.

function-instrument fun_X() fun_Y() fun_Z() = Don’t ignore these three functions from these three files from instrumentation.

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