For the past years whenever I needed to lint or test a single file I would:

• right click it in the navigation tree
• copy relative path
• open the built in terminal with Command-J
• Control-R to search recent commands for 'npm run test' or 'npm run lint'
• Select old path in the command and paste with path I want to test
• hit Enter
• wait

Over time doing this adds up. Recently I stumbled upon VS Code Tasks and found a way to speed things up. By configuring the following tasks.json:

{
    "version": "2.0.0",
    "tasks": [
        {
            "type": "shell",
            "label": "test single xxxxx file",
            "command": "npm run test -- ${file} --coverage=false",
            "problemMatcher": []
        },
        {
            "type": "shell",
            "label": "lint and fix single file xxxxx file",
            "command": "./node_modules/.bin/eslint ${file} --fix",
            "problemMatcher": []
        },
    ]
}

Now to test the file that I'm currently working on I:

• Command-Shift-P to bring up commands input
• Usually 'Tasks: Run Task' is the last run command so just press Enter, In the case it is not typing 'Task' is enough to bring it up
• Then the lint and test tasks appier in the drop down and all I have to do is hit Enter again
• wait
• profit

Don't know why I held out on customizing VS Code so long! Wonder what other time saving features there are?

source: vs code docs