You are migrating a legacy Selenium TestNG framework to Cucumber BDD. What is your migration strategy?

<!-- Add Cucumber to existing pom.xml — keep TestNG -->
<dependency>
    <groupId>io.cucumber</groupId>
    <artifactId>cucumber-java</artifactId>
    <version>7.15.0</version>
</dependency>
<dependency>
    <groupId>io.cucumber</groupId>
    <artifactId>cucumber-testng</artifactId>
    <version>7.15.0</version>
</dependency>
<dependency>
    <groupId>io.cucumber</groupId>
    <artifactId>cucumber-picocontainer</artifactId>
    <version>7.15.0</version>
</dependency>

// EXISTING Page Object (no changes needed)
public class LoginPage {
    public LoginPage(WebDriver driver) { ... }
    public void enterUsername(String u) { ... }
    public void enterPassword(String p) { ... }
    public void clickLogin()            { ... }
}

// NEW Cucumber Step Definition — calls same Page Object
public class LoginSteps {
    private final ScenarioContext ctx;
    public LoginSteps(ScenarioContext ctx) { this.ctx = ctx; }

    @Given("the user is on the login page")
    public void navigateToLogin() {
        ctx.loginPage = new LoginPage(ctx.driver);
        ctx.driver.get(ConfigReader.getBaseUrl() + "/login");
    }

    @When("the user logs in with username {string} and password {string}")
    public void login(String user, String pass) {
        ctx.loginPage.enterUsername(user);  // same method call
        ctx.loginPage.enterPassword(pass);
        ctx.loginPage.clickLogin();
    }
}

Conversion priority:
1. Happy path / smoke tests (highest business value)
2. Tests that BAs/POs want to review (living documentation value)
3. Tests that are frequently run and change often
4. Complex data-driven tests (Scenario Outline replaces TestNG @DataProvider)

Defer migration:
5. Internal unit/integration tests (keep in TestNG)
6. Tests with complex setup that won''t benefit from Gherkin

<!-- testng.xml — run both during transition -->
<suite name="Migration Suite" parallel="tests" thread-count="2">

    <test name="Legacy TestNG Tests">
        <classes>
            <class name="tests.legacy.LoginTest"/>
            <class name="tests.legacy.CheckoutTest"/>
        </classes>
    </test>

    <test name="New Cucumber BDD Tests">
        <classes>
            <class name="runners.CucumberSmokeRunner"/>
        </classes>
    </test>
</suite>

As Cucumber coverage for a feature reaches 100%:
1. Verify Cucumber tests cover all cases the old tests covered
2. Run both suites in parallel for 2 sprints — confirm same results
3. Delete old TestNG test class
4. Update testng.xml to remove deleted class

// BEFORE: TestNG
@DataProvider
public Object[][] loginData() {
    return new Object[][] {
        {"admin@test.com", "Admin@123", "Dashboard"},
        {"user@test.com",  "User@456",  "Home"}
    };
}
@Test(dataProvider = "loginData")
public void testLogin(String email, String pass, String page) { ... }

// AFTER: Cucumber
Scenario Outline: Login with <role>
  When the user logs in as "<email>" with "<password>"
  Then they should land on the "<page>" page
  Examples:
    | email          | password  | page      |
    | admin@test.com | Admin@123 | Dashboard |
    | user@test.com  | User@456  | Home      |

Week 1: Framework setup + first 5 feature files (smoke)
Week 2-3: High-priority tests (20 feature files)
Week 4-5: Remaining tests (25 feature files)
Week 6: Remove old TestNG tests, final validation