Real-world engineering

src/main/java/pages/    LoginPage, ProductsPage...
src/main/java/utils/    ConfigReader, DriverFactory
src/test/java/tests/    LoginTest, api/...
src/test/resources/     config.properties, testdata/

# config.properties
baseUrl=https://www.saucedemo.com
headless=false
// ConfigReader.get(key):
return System.getProperty(key, props.getProperty(key));
mvn test "-DbaseUrl=https://staging.example.com"

ChromeOptions o = new ChromeOptions();
if (Boolean.parseBoolean(ConfigReader.get("headless"))) {
  o.addArguments("--headless=new");
  o.addArguments("--window-size=1920,1080"); // ALWAYS
}
return new ChromeDriver(o);

on: [push]  + workflow_dispatch + schedule (cron)
steps: checkout@v4 -> setup-java@v4 (temurin 21)
       -> mvn -B test -Dheadless=true
upload-artifact@v4 if: failure()
  path: screenshots/ + target/surefire-reports/

junit.jupiter.execution.parallel.enabled=true
junit.jupiter.execution.parallel.mode.default=same_thread
junit.jupiter.execution.parallel.mode.classes.default=concurrent
# classes parallel, methods sequential = safe default

"0 2 * * *"  =  every day at 02:00 UTC
 |  |  | | |
 |  |  | | +-- day of week (0 = Sunday)
 |  |  | +---- month
 |  |  +------ day of month
 |  +--------- hour
 +------------ minute

# repo Settings -> Secrets and variables -> Actions
env:
  APP_PASSWORD: ${{ secrets.APP_PASSWORD }}
# never commit credentials — read them from env in CI
![tests](https://github.com/YOU/repo/actions/workflows/tests.yml/badge.svg)

• Only in CI → headless window size, first suspect
• Only in parallel → shared state; hunt the static
• Only sometimes → missing explicit wait