How to Write Test Cases for Automation Testing?

Test automation is about speed, scale, and precision. As software teams ship faster, the pressure on QA increases, but manual testing can’t keep up with that speed. You need a way to validate key workflows without slowing things down.

That’s where automation testing come in to save the day. With some good automation test cases, you are going to significantly speed up your testing and reduce release time.

In this guide, I am going to show you how to write test cases for automation testing, and the best practices for it.

Let's dive right in!

What are automation test cases?

At their core, automation test cases are scripted instructions that simulate user behavior and validate the outcome. They define four things:

• Preconditions: What must be true before the test runs (e.g. user logged in, database seeded)

• Test Steps: The sequence of interactions to simulate (e.g. fill form, click submit)

• Expected Results: What the system should do (e.g. show success message, redirect to dashboard)

• Actual Results: What actually happened when the script ran

But here’s the nuance: you can’t just copy-paste your manual test cases into a script. Automation has different constraints. It needs to be stable, repeatable, and code-aware.

Manual testers rely on intuition. Automation relies on clarity. So test cases must be purpose-built with automation in mind, i.e. minimal UI dependency, clear assertions, isolated flows.

📚 Read More: 9 Core Benefits of Test Automation

Why writing good automation test cases matters

Good automation test cases pay off in every sprint. Here’s why:

• Faster regression cycles: What used to take days now runs in hours, or even less.

• Consistent results: No more human error. The same steps, the same checks, every time.

• Scalability: Run the same test across browsers, devices, and environments.

• Team velocity: QA shifts from bottleneck to accelerator. Developers get feedback faster, and bugs are caught earlier.

But automation should not be seen as a silver bullet. The value comes from choosing the right things to automate, not trying to automate everything.

💡 Pro tip: Focus on flows that are stable, high-impact, and repeatable. Skip anything that’s volatile or hard to assert.

How to decide what to automate?

Test automation should start where it makes the most impact.

Best test scenarios for automation

• Login and registration flows: Critical paths users hit daily. Simple but important.

• Form validations: Check both success (valid inputs) and failure (invalid inputs).

• Backend verifications: Confirm database updates or API responses — ideally through integration tests, not the UI.

• Smoke and regression tests: Repetitive and essential. Perfect for automation.

• Cross-browser and platform tests: Ensure consistency across environments.

These are high-leverage tests: small effort, big payoff.

What NOT to automate

• Rapidly changing UIs: Automation breaks easily when the UI keeps shifting.

• Highly visual features: Layout bugs, image alignment are best left to human eyes.

• Exploratory scenarios: The whole point is flexibility. Don’t script curiosity.

💡 Pro tip: End-to-end UI tests are expensive to build and maintain. Use them sparingly: only for business-critical flows. For everything else, lean on unit and integration tests.

Key elements of an automation test case

Automation thrives on clarity. Every test case should include the following:

How to create an automation test case

Let's create a test case for the Etsy login popup:

pip install selenium

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.common.keys import Keys
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.chrome.options import Options
from webdriver_manager.chrome import ChromeDriverManager

# Set up Chrome options
chrome_options = Options()
chrome_options.add_argument("--headless")  # Run in headless mode if you don’t need a UI

# Initialize the WebDriver
driver = webdriver.Chrome(service=Service(ChromeDriverManager().install()), options=chrome_options)

try:
    # Navigate to Etsy login page
    driver.get("https://www.etsy.com/signin")

    # Find the email and password fields and the login button
    email_field = driver.find_element(By.ID, "join_neu_email_field")
    password_field = driver.find_element(By.ID, "join_neu_password_field")
    login_button = driver.find_element(By.XPATH, "//button[@type='submit']")

    # Enter credentials (Replace with valid credentials)
    email_field.send_keys("your-email@example.com")
    password_field.send_keys("your-password")

    # Click the login button
    login_button.click()

    # Add assertions or further actions as needed
    # For example, check if login was successful
    # account_menu = driver.find_element(By.ID, "account-menu-id")
    # assert account_menu.is_displayed(), "Login failed"

finally:
    # Close the browser
    driver.quit()

The bottom line