This tutorial will show you all the steps required to build a basic Docker image that can be used to run Prancer in any Docker based environment. This tutorial doesn't show how to use Docker nor Prancer but more how to use it in a CI/CD context that leverages Docker containers.

Before taking this tutorial, ensure the following:

  1. You have the Docker engine installed (Link to Ubuntu flavor)

Then, you can follow these steps:

  1. Create a Prancer image for Docker
  2. Create a Prancer project
  3. Run the tests
  4. Trigger a failure
  5. Cleanup and rejoice

Create a Prancer image for Docker

First, we'll need to setup Prancer into a Docker image. Let's create the standard Dockerfile and add the following content to it:


FROM ubuntu

RUN DEBIAN_FRONTEND=noninteractive apt update -y && \
    DEBIAN_FRONTEND=noninteractive apt install -y python3 python3-pip mongodb git && \
    pip3 install prancer-basic

CMD prancer
WORKDIR /prancer/project

This creates a simple image that contains Prancer, MongoDB and Git. Depending on the configuration of your projet, you may need additional tools installed.

Now let's build the image:

 cd tests/prancer
 docker build docker --tag prancer

Once this is done, you'll have the image built and tagged into your system. It should output a log that looks like this:

Sending build context to Docker daemon  22.53kB
Step 1/4 : FROM ubuntu
---> 4c108a37151f
Step 2/4 : RUN DEBIAN_FRONTEND=noninteractive apt update -y && DEBIAN_FRONTEND=noninteractive apt install -y python3 python3-pip mongodb git && pip3 install prancer-basic
---> Using cache
---> d8f616cda4d4
Step 3/4 : CMD prancer
---> Using cache
---> 48cae0b129df
Step 4/4 : WORKDIR /prancer/project
---> Using cache
---> b34102a2985a
Successfully built b34102a2985a
Successfully tagged prancer:latest

If you list your images, you should see the Prancer image we just built:

docker images

REPOSITORY      TAG         IMAGE ID            CREATED              SIZE
prancer         latest      b34102a2985a        About a minute ago   1.12GB

We can now build our Prancer project.


There is a known limitation with the software right now, you cannot setup MongoDB anywhere else than on the machine you run Prancer. This is why we are installing MongoDB server directly into the container.

There are workarounds such as reverse tunneling the port 27017 into a container or server but that makes it even more complex. We are actively working on a solution!

Create a Prancer project

Next, we'll need a Prancer project. To run tests against a Git repository, well, you need a Git repository with files in it. This portion will create such as repository along with the files for the Prancer project. We'll commit files to it and then configure the Git connector for that specific repository and project.


    "webserver": {
        "port": 80




level = DEBUG
propagate = true
logFolder = log
dbname = whitekite

dbname = validator

reportOutputFolder = validation

containerFolder = validation
database = false


    "fileType": "structure",
    "companyName": "prancer-test",
    "gitProvider": "",
    "private": false


Remember to substitute the gitProvider with your own!


    "fileType": "snapshot",
    "snapshots": [
            "source": "gitConnector",
            "type": "git",
            "testUser": "git",
            "nodes": [
                    "snapshotId": "1",
                    "type": "json",
                    "collection": "security_groups",
                    "path": "data/config.json"


    "fileType": "test",
    "snapshot": "snapshot",
    "testSet": [
            "testName ": "Ensure configuration uses port 80",
            "version": "0.1",
            "cases": [
                    "testId": "1",
                    "rule": "{1}.webserver.port=80"

Then commit this setup to a repository that is accessible using git such as on GitHub. Note that you must create the repository beforehand.

git init
git remote add origin
git add .
git commit -m "Tutorial on jenkins"
git push

Following this, you should be able to see your code on your repository.


You can just use if you want, it contains exactly the same thing.

Run the tests

Once you are ready to execute your tests, you can run the following command to start a snapshot and a testing phase:

docker run --rm -it -v "$(pwd)/tests/prancer/project:/prancer/project" prancer bash -c "service mongodb restart && prancer git"

Let's deconstruct this to understand each part:

  1. docker run --rm -it

    The standard command that will run an image with terminal emulation, input support and kill the container once the process is done!

  2. -v "$(pwd)/tests/prancer/project:/prancer/project"

    This part tells Docker to map the current directory's /tests/prancer/project folder to /prancer/project inside the container. This is necessary because Prancer is configured to execute from that directory. You can override the working directory using -w <folder> and map the project somewhere else but it won't give you any added benefit.

    Note that by binding this, your logs will be put in the mounted volume which means you won't lose them once the process is done. Because of the MongoDB limitation though, you will lose your MongoDB data if you don't add an additional `-v "$(pwd)/mongo:/data/db". This isn't critical but can be favorable depending on your testing approach.

  3. prancer

    This is simply the image name. If you tagged the image name differently when you built it earlier, change this.

  4. bash -c "service mongodb restart && prancer git"

    This is the command that we'll execute in the container. The command needs to be complex in this case because we have a limitation due to MongoDB needing to be started when the container gets activated. If you do not string the 2 commands back to back like this, Prancer will complain that it cannot connect to MongoDB.

    The last part of the command is the Prancer container to validate. In this case, we called it git. If you renamed the container in tests/prancer/project/validation then you need to change this here.

Once this has run, you can find a tests/prancer/project/validation/git/output-test.json in the container folder and a log file in the log/ folder. The exit code of the tool (echo ?$) should return 0 stating that everything went well. The log should look something like:

2019-07-22 18:04:47,533(rule_interpreter: 169) - LHS: 80, OP: =, RHS: 80
2019-07-22 18:04:47,533(rundata_utils:  92) - END: Completed the run and cleaning up.
2019-07-22 18:04:47,533(rundata_utils: 102) -  Run Stats: {
    "start": "2019-07-22 18:04:46",
    "end": "2019-07-22 18:04:47",
    "errors": [],
    "host": "3eb17c24a573",
    "timestamp": "2019-07-22 18:04:46",
    "log": "/prancer/project/log/20190722-180445.log",
    "duration": "1 seconds"

Which shows that the test ran fine trying to compare port 80 to port 80.

Triggering a failure

Now that we have passing tests, let's trigger a simple failure to see how everything fits together. To achieve this, we'll need to create a configuration drift, that is, change something in the data/config.json file that doesn't match the expected tests.

  1. Change the port 80 in there for 443
  2. Save and push the changes to your git repository

Now, if you run the tests again:

docker run --rm -it -v "$(pwd)/tests/prancer/project:/prancer/project" prancer bash -c "service mongodb restart && prancer git"

You should have a failing state proving that the drift was indeed detected. The log should look something like:

2019-07-22 18:08:58,837(rule_interpreter: 169) - LHS: 443, OP: =, RHS: 80
2019-07-22 18:08:58,837(rundata_utils:  92) - END: Completed the run and cleaning up.
2019-07-22 18:08:58,838(rundata_utils: 102) -  Run Stats: {
    "start": "2019-07-22 18:08:57",
    "end": "2019-07-22 18:08:58",
    "errors": [],
    "host": "8531f1a4c4f0",
    "timestamp": "2019-07-22 18:08:57",
    "log": "/prancer/project/log/20190722-180857.log",
    "duration": "1 seconds"

Which shows that the test ran fine trying to compare port 443 to port 80, which obviously fails!

Cleanup your resources

Because this tutorial asked you to create a temporary Git repository on a public service, it would be good if you destroyed it since you won't need it anymore.

Apart from that, no other resources should have been created.


That's it, you are done. You now know how to create a working Docker image with Prancer in it.

Thank you for completing this tutorial on Prancer.

We hope to see you in the next tutorial!