Avoid GitHub action buffering - github

Question

I have a Github repo that contains some Linux utilites.
To run test I use GitHub actions and some simple custom workflow that runs on a remote Linux server using self-hosted runner:
name: CMake
on: [push]
env:
BUILD_TYPE: Release
jobs:
build:
runs-on: self-hosted
steps:
- uses: actions/checkout#v2
- name: Build
working-directory: ${{runner.workspace}}/Utils
shell: bash
run: cmake --build . --config $BUILD_TYPE
- name: Run test
working-directory: ${{runner.workspace}}/Utils
shell: bash
run: ./testing/test.sh
The workflow is very simple - I compile the source using cmake and then run a script from the same repo to test the build. The test script is a bash script and looks as following:
#!/bin/bash
export LD_LIBRARY_PATH=/path/to/bin
cd /path/to/bin
echo -e "Starting the tests"
./run_server &
./run_tests
if [ $? -eq 0 ]; then
echo "successful"
else
echo "failed"
exit 1
fi
Here the scripts starts up an compiled application from my code (run_server) and then run the testing utility that communicates with it and prints a result.
Actually I use C printf() inside run_tests to print the output strings. If I run that on a local machine I get output like the following:
Starting the tests
test1 executed Ok
test2 executed Ok
test3 executed Ok
successful
Each test takes about 1 sec. so I the application prints a line like testX executed Ok one per second.
But if it runs using Github actions the output looks a bit different (copied from the Github actions console):
./testing/test.sh
shell: /bin/bash --noprofile --norc -e -o pipefail {0}
env:
BUILD_TYPE: Release
Starting the tests
successful
And even in this case the output from the bash script printed out only after the script has finished.
So I have 2 problems:
no printf() output from the test application
the script output (printed using echo) come only after the script has finished
I expected the same behavior from the Github action as I get on a local machine i.e. I see a lines printed ~ 1/sec. immediately.
It looks like Github action buffers all the output until a step executed and ignores all the print from the application that run inside the bash script.
Is there a way to get all the output in real time while a step executes?