docker.md

The docker image

Kcov has a docker image: kcov/kcov and tags since v31.

There is two variants (tags):

• latest or vXX that are Debian based
• latest-alpine or vXX-alpine that are Alpine based

Permissions

kcov needs access the following system calls:

• ptrace
• process_vm_readv/process_vm_writev
• personality

You may need to use --security-opt seccomp=unconfined as a docker run option to attach to processes.

Copy into your image

You may want to copy kcov into your image to avoid building it.

# Copy kcov (use kcov/kcov:latest-alpine for Alpine based images)
COPY --from=kcov/kcov:latest /usr/local/bin/kcov* /usr/local/bin/
# If you need documentation
COPY --from=kcov/kcov:latest /usr/local/share/doc/kcov /usr/local/share/doc/kcov

Python + bats example

# The base layer of your image
FROM python:3.11-slim-bookworm

# Install kcov run-time dependencies and bats.
RUN apt-get update && \
    apt-get install --yes --no-install-suggests --no-install-recommends \
      libbfd-dev \
      libcurl4 \
      libdw1 \
      zlib1g \
      bats \
      && \
    apt-get clean && \
    rm -rf /var/lib/apt/lists/*

# Copy kcov (use kcov/kcov:latest-alpine for Alpine based images)
COPY --from=kcov/kcov:latest /usr/local/bin/kcov* /usr/local/bin/
COPY --from=kcov/kcov:latest /usr/local/share/doc/kcov /usr/local/share/doc/kcov

WORKDIR /code

CMD ["bats"]

Test it

test.sh

#!/usr/bin/env bats

source script.sh

@test "test outputNumber function" {
  result="$( outputNumber )"
  [ "$result" -eq 7 ]
}

@test "kcov version" {
  kcov --version | grep -q -c -F "v"
  [ "$?" -eq 0 ]
}

script.sh

outputNumber() {
  echo 7
}

Run tests

# build our image
docker build ./ -t py-bats
# test the built image
docker run --rm -it -v $PWD:/code py-bats kcov --include-path=/code --dump-summary ./coverage bats ./test.sh
# See the coverage result in ./coverage
# Browse the file coverage/index.html in your browser