BDD stands for Behavior-Driven Development — it’s an evolution of TDD (Test-Driven Development) that focuses on how the software should behave from the user’s point of view.
Instead of writing tests in a technical way, BDD describes them in natural, human-readable language — usually using the Given–When–Then format.
💡 Simple Example
Let’s say we’re building a login feature.
BDD Scenario (in plain English):
Feature: User Login
Scenario: Successful login
Given the user is on the login page
When the user enters valid credentials
Then the user should be redirected to the dashboard
This describes behavior, not implementation details.
🧩 Example in Code (Python + Behave)
# features/login.feature
Feature: User Login
Scenario: Successful login
Given the user is on the login page
When the user enters valid credentials
Then the user should see the dashboard
# features/steps/login_steps.py
from behave import given, when, then
@given('the user is on the login page')
def step_user_on_login_page(context):
context.page = "login"
@when('the user enters valid credentials')
def step_user_enters_credentials(context):
context.logged_in = True
@then('the user should see the dashboard')
def step_user_sees_dashboard(context):
assert context.logged_in is True
✅ In Short
| Concept | TDD | BDD |
|---|---|---|
| Focus | Code correctness | User behavior |
| Language | Technical (unit tests) | Natural (Given–When–Then) |
| Goal | Make code work | Make behavior right |