Testing

Guidelines

• Do write tests against a live system as much as possible.
• Do not use mocks if you can avoid it; they tend to lead to tests that are brittle in the face of refactoring.
• Do not use stubs if you can help it; better to test real code than fake code.
• Do test for the outcome of running code; if your tests would break if you refactored the underlying code then your test is too coupled to the implementation.

Running tests

Unit Tests

Note: Unit tests are those in files with extension .unit.test.ts.

1. Make sure you have compiled all code (done automatically when using incremental building)
2. Ensure you have disabled breaking into 'Uncaught Exceptions' when running the Unit Tests
3. For the linters and formatters tests to pass successfully, you will need to have those corresponding Python libraries installed locally
4. Run the Tests via the Unit Tests launch option.

You can also run them from the command-line (after compiling):

npm run test:unittests  # runs all unit tests
npm run test:unittests -- --grep='<NAME-OF-SUITE>'

To run only a specific test suite for unit tests: Alter the launch.json file in the "Debug Unit Tests" section by setting the grep field:

    "args": [
        "--timeout=60000",
        "--grep", "<suite name>"
    ],

...this will only run the suite with the tests you care about during a test run (be sure to set the debugger to run the Debug Unit Tests launcher).

Functional Tests

Functional tests are those in files with extension .functional.test.ts. These tests are similar to system tests in scope, but are run like unit tests.

You can run functional tests in a similar way to that for unit tests:

• via the "Functional Tests" launch option, or
• on the command line via npm run test:functional

System Tests

Note: System tests are those in files with extension .test*.ts but which are neither .functional.test.ts nor .unit.test.ts.

1. Make sure you have compiled all code (done automatically when using incremental building)
2. Ensure you have disabled breaking into 'Uncaught Exceptions' when running the Unit Tests
3. For the linters and formatters tests to pass successfully, you will need to have those corresponding Python libraries installed locally by using the ./requirements.txt and build/test-requirements.txt files
4. Run the tests via npm run or the Debugger launch options (you can "Start Without Debugging").
5. Note you will be running tests under the default Python interpreter for the system.

You can also run the tests from the command-line (after compiling):

npm run testSingleWorkspace  # will launch the VSC UI
npm run testMultiWorkspace  # will launch the VSC UI

Customising the Test Run

If you want to change which tests are run or which version of Python is used, you can do this by setting environment variables. The same variables work when running from the command line or launching from within VSCode, though the mechanism used to specify them changes a little.

• Setting CI_PYTHON_PATH lets you change the version of python the tests are executed with
• Setting VSC_PYTHON_CI_TEST_GREP lets you filter the tests by name

CI_PYTHON_PATH

In some tests a Python executable is actually run. The default executable is python (for now). Unless you've run the tests inside a virtual environment, this will almost always mean Python 2 is used, which probably isn't what you want.

By setting the CI_PYTHON_PATH environment variable you can control the exact Python executable that gets used. If the executable you specify isn't on $PATH then be sure to use an absolute path.

This is also the mechanism for testing against other versions of Python.

VSC_PYTHON_CI_TEST_GREP

This environment variable allows providing a regular expression which will be matched against suite and test "names" to be run. By default all tests are run.

For example, to run only the tests in the Sorting suite (from src/test/format/extension.sort.test.ts) you would set the value to Sorting. To run the ProcessService and ProcessService Observable tests which relate to stderr handling, you might use the value ProcessService.*stderr.

Be sure to escape any grep-sensitive characters in your suite name.

In some rare cases in the "system" tests the VSC_PYTHON_CI_TEST_GREP environment variable is ignored. If that happens then you will need to temporarily modify the const grep = line in src/test/index.ts.

Launching from VS Code

In order to set environment variables when launching the tests from VSCode you should edit the launch.json file. For example you can add the following to the appropriate configuration you want to run to change the interpreter used during testing:

    "env": {
        "CI_PYTHON_PATH": "/absolute/path/to/interpreter/of/choice/python"
    }

On the command line

The mechanism to set environment variables on the command line will vary based on your system, however most systems support a syntax like the following for setting a single variable for a subprocess:

VSC_PYTHON_CI_TEST_GREP=Sorting npm run testSingleWorkspace

Testing Python Scripts

The extension has a number of scripts in ./pythonFiles. Tests for these scripts are found in ./pythonFiles/tests. To run those tests:

• python2.7 pythonFiles/tests/run_all.py
• python3 -m pythonFiles.tests

By default, functional tests are included. To exclude them:

python3 -m pythonFiles.tests --no-functional

To run only the functional tests:

python3 -m pythonFiles.tests --functional

Debugging

The extension itself

Clone the repo into any directory, open that directory in V SCode, and use the Extension launch option within VS Code.

debugpy integration

The easiest way to debug the Python Debugger (in our opinion) is to clone this git repo directory into your extensions directory. From there use the Extension + Debugger launch option.