vscode-python: Debugger won't step over or into code

Environment data

• VS Code version: 1.22.2
• Extension version (available under the Extensions sidebar): 2018.4.0
• OS and version: MacOS X High Sierra
• Python version (& distribution if applicable, e.g. Anaconda): 3.6.5 homebrew installed
• Type of virtual environment used (N/A | venv | virtualenv | conda | …): venv
• Relevant/affected Python packages and their versions: pytest?

Actual behavior

When I set a breakpoint in a unit test, and run “debug test”, the debugger pauses correctly on the breakpoint, but I can’t step into or over using the buttons in the GUI. Whenever I press either button, the debugger next breaks at testlauncher.py on sys.exit().

The test does run to completion. Whilst at the breakpoint, the debugger works otherwise, e.g. I can see locals, use the console, etc.

Python and pytest are both set to the binaries in my venv. Linting (flake8) and running of individual tests are both working.

    "python.pythonPath": "/Users/maraspeli/Build/Python/jira-metrics/bin/python",
    "python.linting.enabled": true,
    "python.linting.flake8Enabled": true,
    "python.linting.flake8Path": "/Users/maraspeli/Build/Python/jira-metrics/bin/flake8",
    "python.unitTest.pyTestEnabled": true,
    "python.unitTest.pyTestPath": "/Users/maraspeli/Build/Python/jira-metrics/bin/pytest",

I get almost the same behaviour if I create and use a launch configuration like this instead of the built-in “debug test” launcher:

        {
            "name": "Python: Tests",
            "type": "python",
            "request": "launch",
            "pythonPath": "${config:python.pythonPath}",
            "program": "python",
            "module": "pytest",
            "args": [
                "-v",
            ],
            "debugOptions": [
                "RedirectOutput"
            ]
        }

The only difference here is that I don’t get paused again at sys.exit(), it just finishes the test run.

Expected behavior

Step over and step into steps through the lines in the file.

Steps to reproduce:

1. Set breakpoint
2. Debug a test
3. Attempt to step over or into a function

Logs

Output for Python in the Output panel (View→Output, change the drop-down the upper-right of the Output panel to Python)

(nothing relevant)

Output from Console under the Developer Tools panel (toggle Developer Tools on under Help)

(nothing relevant)