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Enable TI for Python

note

Currently, TI for Python is behind the feature flag CI_PYTHON_TI. Contact Harness Support to enable the feature.

Using Test Intelligence in your Harness CI pipelines doesn't require you to change your build and test processes, but some initial set up is required.

Set up Test Intelligence for Python​

To use TI for Python, you must:

  1. Use Python 3.
  2. Add a Run Tests step.
  3. Generate the initial call graph.
  4. Trigger test selection.
  5. View test reports and test selection.

After you've successfully enabled TI, you can further optimize test times by enabling parallelism (test splitting) for TI. You can also configure TI to ignore tests or files.

Add the Run Tests step​

You need a CI pipeline with a Build stage where you'll add the Run Tests step. If you haven't created a pipeline before, try one of the CI pipeline tutorials or go to CI pipeline creation overview.

The build environment must have the necessary binaries for the Run Tests step to execute your test commands. Depending on the stage's build infrastructure, Run Tests steps can use binaries that exist in the build environment or pull an image, such as a public or private Docker image, that contains the required binaries. For more information about when and how to specify images, go to the Container registry and image settings.

  1. In Harness, go to the pipeline where you want to add the RunTests step. In the CI stage, add a RunTests step and configure the Run Tests step settings. To enable Test Intelligence, you must:

    • Specify one or more report paths in reports. JUnit XML format is required. For more information, go to Format test reports.
    • Include runOnlySelectedTests: true
    • Specify language, buildTool, args, and other settings specific to your selected language or tool.
    • Include connectorRef and image if required by the build infrastructure.

  2. After adding the RunTests step, make sure you generate the initial call graph.

Here is a YAML example of a Run Tests step configured for Python.

              - step:
                  type: RunTests
                  name: Run Python Tests
                  identifier: Run_Python_Tests
                  spec:
                    language: Python
                    buildTool: Pytest
                    runOnlySelectedTests: true
                    preCommand: |
                      python3 -m venv .venv
                      . .venv/bin/activate

                      python3 -m pip install -r requirements/test.txt
                      python3 -m pip install -e .

Generate the initial call graph​

The first time you enable Test Intelligence on a repository, you must run all tests and generate an initial call graph. This sets the baseline for test selection in future builds. You can use a webhook trigger or manual build to generate the initial call graph.

info

The initial call graph sets the baseline for test selection in future builds. Test selection isn't applied to this run because Harness has no baseline against which to compare changes and select tests.

You only need to generate an initial call graph the first time you enable Test Intelligence on a repository.

  1. Add a webhook trigger to your pipeline that listens for Pull Request or Push events in the pipeline's codebase.

  2. Open a PR or push changes to your codebase.

  3. Wait while the build runs. You can monitor the build's progress on the Build details page. If the build succeeds, you can review the test results.

    The first run with TI doesn't apply test selection, because Harness must establish a baseline for comparison in future runs.

  4. If you created a PR, merge the PR after the tests pass and the build succeeds. This is required to ensure that the baseline established by the call graph persists on the target branch. This step is not required for push triggers.

Now that you've established a testing baseline, each time this pipeline runs, Harness can select relevant tests to run based on the content of the code changes.

Trigger test selection​

After you generate the initial call graph, Harness can apply test selection to subsequent pipeline runs.

To trigger test selection, create another PR (or push changes to your codebase) and run the pipeline again.

  1. Open a PR or push changes to your codebase.
  2. Wait while the trigger starts and runs your pipeline. You can monitor the build's progress on the Build details page.
  3. If the build succeeds, you can review the test results and test selection.
  4. If the tests pass and the build succeeds, you can merge your PR, if applicable.

Each time the pipeline runs, Harness selects the relevant tests to run based on the content of the code changes.

View test reports and test selection​

For information about test reports for Test Intelligence, go to View tests.

Pipeline YAML examples​

This example shows a pipeline that uses Harness Cloud build infrastructure and runs tests on Python with pytest and Test Intelligence.

pipeline:
  name: Test Intelligence Demo
  identifier: testintelligencedemo
  projectIdentifier: default
  orgIdentifier: default
  properties:
    ci:
      codebase:
        build: <+input>
        connectorRef: YOUR_CODEBASE_CONNECTOR_ID
  stages:
    - stage:
        type: CI
        identifier: Build_and_Test
        name: Build and Test
        spec:
          cloneCodebase: true
          execution:
            steps:
              - step:
                  type: RunTests
                  name: Run Python Tests
                  identifier: Run_Python_Tests
                  spec:
                    language: Python
                    buildTool: Pytest ## Specify pytest or unittest
                    runOnlySelectedTests: true  ## Set to false if you don't want to use TI.
                    preCommand: |
                      python3 -m venv .venv
                      . .venv/bin/activate

                      python3 -m  pip install pytest
                      python3 -m pip install -r requirements/dev.txt
                      python3 -m pip install -e .
                    envVariables:
                      PYTHONPATH: /harness ## Exclude if not applicable.
          platform:
            arch: Amd64
            os: Linux
          runtime:
            spec: {}
            type: Cloud

Run Tests step settings​

The Run Tests step has the following settings. Some settings are optional, and some settings are only available for specific languages or build tools. Settings specific to containers, such as Set Container Resources, are not applicable when using the step in a stage with VM or Harness Cloud build infrastructure.

Name​

Enter a name summarizing the step's purpose. Harness automatically assigns an Id (Entity Identifier Reference) based on the Name. You can edit the Id.

Name and Id are required. Description is optional.

Container Registry and Image​

The build environment must have the necessary binaries for the Run Tests step to execute your test commands. Depending on the stage's build infrastructure, Run Tests steps can use binaries that exist in the build environment or pull an image, such as a public or private Docker image, that contains the required binaries. You can also install tools at runtime in Pre-Command, provided the build machine or image can execute the necessary commands, such as curl commands to download files.

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The stage's build infrastructure determines whether these fields are required or optional:

For Container Registry, provide a Harness container registry connector, such as a Docker connector, that connects to the container registry where the Image is located.

For Image, provide the FQN (fully-qualified name) or artifact name and tag of a Docker image that has the binaries necessary to run the commands in this step, such as python:latest. If you don't include a tag, Harness uses the latest tag.

You can use any Docker image from any Docker registry, including Docker images from private registries. Different container registries require different name formats:

  • Docker Registry: Enter the name of the artifact you want to deploy, such as library/tomcat. Wildcards aren't supported. FQN is required for images in private container registries.
  • ECR: Enter the FQN of the artifact you want to deploy. Images in repos must reference a path, for example: 40000005317.dkr.ecr.us-east-1.amazonaws.com/todolist:0.2.
  • GCR: Enter the FQN of the artifact you want to deploy. Images in repos must reference a path starting with the project ID that the artifact is in, for example: us.gcr.io/playground-243019/quickstart-image:latest.

Language​

Select Python.

Build Tool​

Select the build automation tool: Pytest or Unittest.

tip

You can use pytest to run unittest.

Build Arguments​

This setting is optional for Python. You can provide additional runtime arguments for tests, such as --junitxml=out_report.xml.

If you include Build Arguments for Python:

  • You don't need to repeat the build tool, such as pytest or unittest; this is declared in Build Tool.
  • You don't need to include coverage flags (--cov or coverage).
  • Python 3 is required. If you use another command, such as python, to invoke Python 3, you must add an alias, such as python3 = "python".
  • The Python 3 binary is required. Python 3 is preinstalled on Harness Cloud runners. For other build infrastructures, the binary must be preinstalled on the build machine, available in the specified Container Registry and Image, or manually installed at runtime in Pre-Command.

Test Report Paths​

This setting is optional for Python.

You can use this setting if you want your test reports to be stored somewhere other than the default location or have a different name than the default report name.

You can specify one or more paths to files that store test results in JUnit XML format. Glob is supported.

                    reports:
                      type: JUnit
                      spec:
                        paths:
                          - out_report.xml*

You can add multiple paths. If you specify multiple paths, make sure the files contain unique tests to avoid duplicates.

Enable Test Splitting and Test Split Strategy​

Used to enable test splitting for TI.

Pre-Command​

You can enter commands for setting up the environment before running the tests. If a script is supplied here, select the corresponding Shell option.

info
  • Python 3 is required to use TI for Python, and you can use Pre-Command to install the Python 3 binary if it is not already installed on the build machine or available in the specified Container Registry and Image. Python 3 is preinstalled on Harness Cloud runners (Harness Cloud build infrastructure).
  • If you use another command, such as python, to invoke Python 3, you must add an alias, such as python3 = "python".
  • You don't need to install coverage tools in Pre-Command. If you install a coverage tool, Harness uses the version you install instead of the included version.
  • You can specify PYTHONPATH in the Environment Variables.

Post-Command​

You can enter commands used for cleaning up the environment after running the tests. For example, sleep 600 suspends the process for 600 seconds.

If a script is supplied here, select the corresponding Shell option.

Run Only Selected Tests​

This option must be selected (true) to enable Test Intelligence.

If this option is not selected (false), TI is disabled and all tests run on every build.

Test Globs​

You can override the default test globs pattern. For example, if the default is *_test.py or test_*.py, you can override it with any other pattern, such as .test.py.

Environment Variables​

You can inject environment variables into the step container and use them in the step's commands. You must input a Name and Value for each variable.

You can reference environment variables in the Build Arguments, Pre-Command, or Post-Command scripts by name, such as $var_name.

Variable values can be fixed values, runtime inputs, or expressions. For example, if the value type is expression, you can input a value that references the value of some other setting in the stage or pipeline.

Using an expression for an environment variable's value.
Stage variables

Stage variables are inherently available to steps as environment variables.

PYTHONPATH​

You can set PYTHONPATH in the step's envVariables, if required. For example:

              - step:
                  type: RunTests
                  name: Run Python Tests
                  identifier: Run_Python_Tests
                  spec:
                    language: Python
                    ...
                    envVariables:
                      PYTHONPATH: /harness

Image Pull Policy​

If you specified a Container Registry and Image, you can specify an image pull policy:

  • Always: The kubelet queries the container image registry to resolve the name to an image digest every time the kubelet launches a container. If the kubelet encounters an exact digest cached locally, it uses its cached image; otherwise, the kubelet downloads (pulls) the image with the resolved digest, and uses that image to launch the container.
  • If Not Present: The image is pulled only if it isn't already present locally.
  • Never: The image is not pulled.

Run as User​

If you specified a Container Registry and Image, you can specify the user ID to use for running processes in containerized steps.

For a Kubernetes cluster build infrastructure, the step uses this user ID to run all processes in the pod. For more information, go to Set the security context for a pod.

Privileged​

For container-based build infrastructures, you can enable this option to run the container with escalated privileges. This is equivalent to running a container with the Docker --privileged flag.

Shell​

Select the shell script type, if you provided Pre-command or Post-command.

Set Container Resources​

These settings specify the maximum resources used by the container at runtime. These setting are only available for container-based build infrastructures, such as a Kubernetes cluster build infrastructure.

  • Limit Memory: The maximum memory that the container can use. You can express memory as a plain integer or as a fixed-point number using the suffixes G or M. You can also use the power-of-two equivalents Gi and Mi. The default is 500Mi.
  • Limit CPU: The maximum number of cores that the container can use. CPU limits are measured in CPU units. Fractional requests are allowed. For example, you can specify one hundred millicpu as 0.1 or 100m. The default is 400m. For more information go to Resource units in Kubernetes.

Timeout​

The timeout limit for the step. Once the timeout is reached, the step fails and pipeline execution proceeds according to any Step Failure Strategy settings or Step Skip Condition settings.

Troubleshooting TI for Python​

If you encounter errors with TI for Python, make sure you have met the following requirements:

  • Your project is written in Python 3, and your repo is a pure Python 3 repo.
  • You don't use resource file relationships. TI for Python doesn't support resource file relationships.
  • You don't use dynamic loading and metaclasses. TI for Python might miss tests or changes in repos that use dynamic loading or metaclasses.
  • Your Build Tool is pytest or unittest.
  • The Python 3 binary is preinstalled on the build machine, available in the specified Container Registry and Image, or installed at runtime in Pre-Command.
  • If you use another command, such as python, to invoke Python 3, you have added an alias, such as python3 = "python".

If you get errors related to code coverage for Python:

  • If you included Build Arguments, these don't need coverage flags (--cov or coverage).
  • You don't need to install coverage tools in Pre-Command.