Command line & npm

The course runs everything from a terminal — installing Playwright, starting the practice app, running tests. If typing commands instead of clicking feels unfamiliar, this page covers the handful you actually need, all drawn from Module 0.

The terminal

A terminal (or command line / shell) is a text window where you type commands and the computer runs them. You’ll see a prompt waiting for input, then you type a command and press Enter. The terminal is always “in” some folder — your current directory — and most commands act relative to it.

Command	Does	Notes
pwd	print working directory	”where am I?” (Windows PowerShell: cd alone)
ls	list files here	Windows: dir
cd foldername	change into a folder	cd .. goes up one level
cd testmarket-lab	enter the app folder	exactly what Module 0 runs

You don’t need to memorise much — cd to move around and ls to look around cover most of it.

Node.js and npm

• Node.js runs JavaScript outside the browser. Playwright is a Node program, so Node is the one prerequisite (the course uses Node 20+). Check yours with node -v.
• npm (Node Package Manager) ships with Node. It installs the libraries your project depends on and runs your project’s scripts.

package.json and node_modules

Every Node project has a package.json — a manifest listing the project’s dependencies (libraries it needs) and scripts (named commands). When you install, npm downloads those dependencies into a node_modules/ folder:

playwright-course/
├── package.json     # dependencies + scripts (you edit this)
├── node_modules/    # the downloaded libraries (never edit; never commit)
└── tests/           # your .spec.ts files

node_modules/ is huge and fully rebuildable, which is why it belongs in .gitignore (see the Git reference).

npm install

npm install          # read package.json, download every dependency
npm install --save-dev @axe-core/playwright   # add a new dev dependency

npm install (often shortened to npm i) is the first thing you run after cloning a project — Module 0 runs it inside testmarket-lab before starting the app.

npm run — running scripts

Scripts defined in package.json are run with npm run <name>:

npm start            # shorthand for `npm run start` — Module 0 starts the app
npm test             # shorthand for `npm run test`
npm run reset        # TestMarket Lab: restore the seed database

start and test are special — they work without the run keyword. Everything else needs npm run <name>.

npx — run without installing

npx runs a package’s command without installing it globally. It’s how the course runs Playwright:

npx playwright test          # run the whole test suite
npx playwright show-report   # open the HTML report
npm init playwright@latest   # scaffold a new Playwright project (Module 0)

The difference in one line: npm install adds a library to your project; npx runs a command, fetching it on the fly if needed.

The Module 0 setup, in order

cd playwright-course
npm init playwright@latest    # scaffold the project (npx under the hood)
npx playwright test           # run the example tests
npx playwright show-report    # view results

# the practice app
cd testmarket-lab
npm install                   # download its dependencies
npm start                     # run it at http://localhost:3000

Quick reference

pwd / ls / cd      where am I / what's here / move around
node -v            check Node is installed (need 20+)
package.json       project manifest: dependencies + scripts
node_modules/      downloaded libraries (gitignored, rebuildable)
npm install        download all dependencies
npm install -D x   add a dev dependency
npm start          run the "start" script
npm test           run the "test" script
npm run <name>     run any other script
npx <cmd>          run a package command without installing it
npx playwright test          run the suite
npx playwright show-report   open the HTML report