Q2 of 21 · BDD / Cucumber

Explain the Given / When / Then structure in Gherkin and what each keyword means.

BDD / CucumberJuniorbddgherkingiven-when-thenscenariosyntax

Short answer

Short answer: Given sets up the precondition (context), When describes the action the user or system takes, Then asserts the expected outcome. And / But extend any of the three without repeating the keyword.

Detail

Gherkin scenarios follow a narrative structure modelled on user stories:

Scenario: Successful login with valid credentials
  Given the user is on the login page
  And   the user has a registered account with email "alice@example.com"
  When  the user enters valid credentials and clicks "Log in"
  Then  the user is redirected to the dashboard
  And   a welcome message "Hello, Alice" is displayed

Given — establishes the system state before the action. Think "context." Typically maps to test setup (navigating to a page, inserting DB rows, mocking an API).

When — the trigger — a user action, API call, or system event. There should usually be one When per scenario. Multiple Whens in a single scenario often signal that you have two scenarios collapsed into one.

Then — the observable outcome. Assertions go here. It should describe what the user sees or what the system state is, not internal implementation details.

And / But — grammatical sugar. "And" continues the previous keyword's intent; "But" adds a contrasting condition:

Then  the order is placed successfully
But   the discount code is not redeemed twice

Good practice: Scenarios should read like a specification, not a test script. Avoid implementation details ("When the user clicks the button with id='submit-btn'") — write what, not how.

// EXAMPLE

Feature: Shopping cart checkout

  Scenario: Guest checkout with valid card
    Given the cart contains 1 item priced at £29.99
    When  the user completes checkout with a valid Visa card
    Then  an order confirmation email is sent to the user
    And   the order status is "confirmed"
    And   the inventory count for that item decreases by 1

// WHAT INTERVIEWERS LOOK FOR

Accurate definitions of all three. The single-When principle. Writing scenarios in terms of user-visible behaviour, not implementation.

// COMMON PITFALL

Putting assertions in the When step or setup in the Then step — each keyword has a clear purpose.

// Related questions

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