How to build E2E test cases?

What if your app’s big debut flops because a single button breaks the whole flow?

In 2022, software quality issues cost U.S. businesses $2.41 trillion. Now, imagine a scenario where you launch a new application.

First, users download and start using it – there will be so much excitement involved.

But then - bang, and those first users can’t make a purchase because the payment gateway fails silently.

In a blink of an eye, excitement turns into a panic mode.

Unfortunately, these scenarios are pretty common. The issues and bugs can slip through the cracks when you do only isolated tests. This is when end-to-end testing is so much needed.

Today, when user expectations rise, the apps become correspondingly more complex. There are increasingly moving parts and interconnected components, such as frontend, backend, APIs, databases, and third-party services. Testing in such a multifaceted environment becomes tough.

Yet, with the right methodology, right tools, and right test cases, it can be done.

The current role of end-to-end testing in software development

End-to-end testing, also known as E2E testing, is important for validating the entire workflow of an application, from the beginning of the user journey to its end. To compare with other testing methods:

As you can see, both unit and integration testing emphasize individual parts.

In turn, E2E testing takes a more holistic approach. It makes sure all the elements function together as a team.

Keep in mind that with the right software testing services vendor, you can get up to 95% test coverage and accelerate development by 30%. No need to spend weeks on holistic testing.

E2E handles frontend interfaces, logic, APIs, databases, and third-party services.

E2E simulates user interactions and confirms the whole system performs as intended under realistic conditions.

Considering that, in some cases, up to 70% of SDLC effort is dedicated to software testing, getting the approach right can help save massively on costs and resources.

The end-to-end testing process is indispensable in CI/CD, testing in Agile, and DevOps. It is a safety net, catching defects that might slip through narrower testing scopes and preventing chaotic, last-minute fixes.

Key E2E benefits for developers, QA teams, and managers

The value of end-to-end software testing use cases goes beyond technical validation. It affects every development team level – from coders to QA professionals to leadership.

E2E creates a ripple effect - it can boost the quality of the product and promote trust across the board. Conversely, ignoring them opens the door to many preventable challenges.

Common pitfalls of skipping end-to-end software testing

The advantages of E2E are clear. What is more, there are some pitfalls E2E testing can help you with. The evidence shows that the cost to fix an error found after product release is four or five times higher compared to the issue uncovered earlier in the cycle. Often, the pitfalls related to the SDLC and testing manifest themselves at the worst possible time. Naturally, it can undermine the entire product.

Here are the four most common pitfalls E2E testing is there to help you with:

1. Unexpected production issues

If your testing teams do not validate workflows with E2E, there might be some serious issues in production later on. The entire checkout process might stall because of the database timeout. As a result, users will be stranded mid-purchase.

How e2e testing helps:

E2E testing looks for potential issues throughout the entire user journey. It makes sure all the components communicate and work together as they should. When simulating real-world scenarios, E2E testing helps identify failures before the product stage is on. As a result, you save costs or mitigate problems before they have a major adverse effect.

2. Higher debugging costs

Identifying critical issues late in the production cycle is significantly more expensive than catching them early. For example, a payment gateway failure discovered post-release may require extensive backtracking and hotfixes, consuming substantial resources. Studies indicate that fixing a bug after release can be up to 100 times more costly than during the design phase.

How e2e testing helps:

Implementing E2E testing during the development phase helps detect and address issues early, reducing the need for costly post-release fixes. This proactive approach not only saves resources but also minimizes potential revenue loss during downtime.

3. Worse user experience

Hidden bugs in critical flows, such as login failures or unresponsive checkout buttons, can erode user trust. A survey revealed that 88% of users would abandon an app due to consistent bugs. Imagine a user abandoning a purchase on an eCommerce site because the “Pay Now” button is unclickable. As frustration mounts, retention will plummet.

How e2e testing helps:

E2E testing is used to make sure users have a smooth experience when using the product. Testing teams get into the user’s shoes, go through the entire user journey, and fix the issues that could frustrate the end-user. As a result, you get a better product offering higher user satisfaction and retention.

4. Potential reputation damage

High-profile failures, such as a banking app crashing during major transactions or compromising sensitive data, can severely tarnish a company's image and drive customers away. A notable example is Sonos, which faced significant backlash and financial losses due to a buggy app rollout, leading to a $500 million debacle and the CEO's resignation.

How e2e testing helps:

E2E testing mitigates the risk of failures, as we mentioned above. E2E testers thoroughly validate the app’s performance under different scenarios. Such diligence helps protect the company’s reputation and foster customer trust.

The pitfalls above show the high stakes of the SLDC and its role in testing. While it may seem like a shortcut and cost less, forgetting about E2E testing may alter and become a costly detour. You don’t want to have a broken product and unsatisfied users on your hands.

The four steps to understand the end-to-end testing process

No, let’s do a thought experiment. You’re launching a fulfillment platform designed to power hundreds and even thousands of daily eCommerce operations. The scope includes everything from multi-storefront management to real-time inventory updates and shipping label generation. Expectations are high. However, the moment the app goes live, major issues surface. The mobile app crashes during key workflows. Order processing lags and takes longer than expected. The system fails to handle basic logistics tasks. Merchants lose trust, orders are delayed, and user churn skyrockets.

End-to-end testing is a structured journey from planning to maintenance. When done right, the methodology turns potential disasters into preventable hiccups. Here are four steps to make sure the end-to-end testing process is approached correctly:

1. Planning

2. Designing

3. Executing

4. Analyzing

Step 1. Planning and defining test objectives

First and foremost, you start by pinpointing critical user journeys. These should be matched against business and technical goals and requirements. Returning to the Soapbox example, the first phase will test account creation, product search, and checkout flows. The rule of thumb dictates to prioritize end-to-end testing examples based on three factors:

1. Risk (payment failures).

2. Impact (revenue loss because of abandoned carts).

3. Frequency (daily logins).

When approaching the first step, set clear acceptance criteria. It can be something like “User completes checkout in under 1 minute.” This will help objectives measure success.

Step 2. Designing effective test cases

Well-designed test cases are the heartbeat of end-to-end testing. Each should include:

Cover positive cases (successful login), negative cases (invalid password), and edge cases (expired session). Avoid redundancy by targeting unique workflows. At the same time, make sure there is comprehensive coverage.

Step 3. Executing tests, manual vs. automated approaches

As the next step, you choose between different approaches. The choice depends on your goals:

What can it look like? You use manual testing and check the new signup flow to make sure it feels intuitive. In turn, you use automated testing to log tests that catch regressions quickly. So, in this manner, both approaches work together for the best results.

Step 4. Analyzing results and maintaining test cases

Finally, after E2E tests are executed, dive deep into the results. Do the following:

1. Capture logs, screenshots, and error messages.

2. Regularly update test cases to match app changes.

3. Track flaky tests and refactor them for reliability.

The above-mentioned processes set the stage for writing great E2E test cases, something we will cover in the next section.

Key principles for writing robust E2E test cases

Crafting practical E2E test cases demands discipline and foresight. These core principles ensure your tests are functional:

Principle #1. Keeping the end-user perspective in mind

E2E should go way beyond technical logic. They must reflect real-world usage.

To achieve that, focus on some critical workflows from the end-user point of view – from account creation to payment processing. A common end-to-end testing scenario can include simulating a user adding some items to a cart, applying a discount code, and checking out with a credit card.

Pro tip from DeviQA: Get into your users’ shoes/ Watch and study them in action. It is possible to catch game-changers by observing real beta sessions. These can be how many folks skip login for a guest checkout.

Principle #2. Structuring test cases for clarity and efficiency

Never forget to adopt a consistent format for your E2E test cases. Such a format should include these:

1. Test ID;

2. Title;

3. Preconditions;

4. Steps;

5. Expected outcome.

Keep these concise. Avoid unnecessary clutter.

Pro tip from DeviQA: Stick to a consistent test case template. It keeps everyone on the testing crew on the same page. Consistent templates speed up reviews and make it easier for newbies to jump in without drowning in chaos.

Principle #3. Handling test data and dependencies correctly

Stable test data is important. It is best to avoid hardcoding dynamic values, such as timestamps. Instead, mock data and APIs should be considered to get consistent inputs. Besides, take care of dependencies. Isolate tests to run them independently. As a result, you will avoid interference.

Pro tip from DeviQA: Ditch the manual data grind. Grab a test data generator. Such a move can turn hours of setup into minutes. It will spit realistic, reusable datasets that work every time.

Principle #4. Managing flaky tests proactively

Flaky tests erode trust. Regarding some common culprits, there are timing issues, such as a page loading slower than expected or sync operations. To deal with these, use intelligent wait strategies. Prioritize them over fixed delays.

Pro tip from DeviQA: Tag every flaky test failure with a timestamp. Also, include an environment snapshot. Leave those breadcrumbs. Later, they will help you trace issues faster.

The four principles transform end-to-end testing from a technical exercise to a user-centric art. When prioritizing clarity, stability, and real-world relevance, you build test cases that catch bugs and improve development.

How to design end-to-end testing that scales

Let’s return to the Soapbox example. Consider the app started as a simple platform with basic functionalities like inventory control, order processing, and logistics. As Soapbox’s user base grew, they added advanced features such as discounted shipping rates, label printing, and automated packaging recommendations. With the additions, the system becomes more complex. Greater complexity requires more rigorous and holistic testing - E2E.

Your E2E test cases that worked like a charm back then? They’re now a tangled mess, breaking with every update and slowing your team to a crawl. In such a context, scalability in end-to-end testing is a lifeline, no less. As apps grow and evolve, your testing strategy must keep up. Keeping that in mind, here’s how you can design E2E testing to match the evolving needs of your product:

Create modular and reusable test scripts

Think of your E2E test cases like a set of LEGO bricks. They are small, versatile pieces you can snap together to build anything. Breaking tests into reusable components is the key to scalability.

Modularity isn’t just about efficiency. It is also about making your app ready for future challenges. For instance, when you add a two-factor authentication (2FA) step to log in, you update only one function, and every test you take will adapt instantly.

End-to-end testing best practices for automation and maintenance

To make the E2E testing framework scalable, you need to take care of several areas. Here’s how to keep your testing game strong as your project grows:

To illustrate: A reusable “add to cart” module might start simple, but as new features like “buy one, get one free” roll out, you update it once with a discount check. Clear documentation notes the change, and refactoring ensures it doesn’t overlap with a separate “apply coupon” script.

Use automation IDs and selectors effectively

Did a test fail because a developer tweaked a button’s style, and its CSS selector vanished?

It’s like trying to find your car in a parking lot after someone repaints it. Stable selectors are the secret sauce to keeping E2E testing reliable as your UI evolves. Ditch fragile CSS or XPath expressions that break with every redesign; lean on data-test attributes, like data-test=“submit-button” for rock-solid reliability. These custom IDs are explicit, developer-friendly, and immune to cosmetic changes.

When adding scalability into end-to-end testing, you need to follow a clear path. It includes using modular scripts, learning smart maintenance habits, and adopting stable selectors. These help deal with new features, face tighter deadlines, and make users happier.

3 steps for building a reliable E2E testing framework

A solid strategy ties everything together. Here’s how to build one.

A solid end-to-end strategy is the one tying everything together. Follow these steps to build such a strategy:

Step 1. Choose the right tools and frameworks

The tools for end-to-end testing include many options. From open-source E2E testing tools to niche frameworks, the choice depends on your needs, resources, and capabilities. For a start, there are E2E testing frameworks that are a good fit:

Considering all the different options, a small team of testers might prefer testing with Cypress because of its simplicity. However, lean toward the Playwright testing process if you have a cross-browser project.

Step 2. Balance manual and automated testing

A good E2E testing framework is all about balance. Instead of “either…or,” use both manual and automated testing approaches. Do manual tests for exploratory checks. Automate testing for repetitive tasks, like login validation.

Step 3. Define an E2E test coverage strategy

Setting priorities is the third step in building a reliable E2E testing framework. Categorize tests by aspects like:

During this phase, the key is to avoid over-testing trivial test cases, such as button colors. Instead, make sure critical workflows are bulletproof.

E2E testing checklist to get you started

Imagine you’re a pilot about to take off. Would you skip checking the fuel, wings, or weather just because the plane looks shiny? Of course not. In such a scenario, end-to-end testing is your pre-flight checklist.

Now, here’s your “pre-flight” checklist for end-to-end testing:

1. Pre-test environment setup

1.1. Reset databases and clear states before each run. Think of it as wiping the slate clean.

1.2. A mismatched environment can hide bugs that pop up later. A payment gateway failing because the test server skipped a firewall rule that production enforces.

1.3. Set up scripts to automate this reset. As a result, your team won’t be bogged down manually scrubbing data.

Rule #1. A solid end-to-end testing process starts with consistency.

2. Test execution and reporting

2.1. Use dashboards in CI/CD tools (e.g., Jenkins, GitHub Actions) to monitor test runs as they happen.

2.2. Pair test runs with detailed logs. Stack traces, network requests, and even browser console outputs make debugging faster.

2.3. Screenshot failures automatically (tools like Playwright do this out of the box) so you can see exactly what a user would’ve seen.

2.4. Generate reports highlighting trends, not just pass/fail counts.

Rule #2. Turn raw data into a story your team can act on.

3. Continuous monitoring and optimization

3.1. Integrate tests into CI/CD pipelines so they fire automatically on every commit. Catch regressions before they sneak into the main branch.

3.2. Carve out time weekly to analyze results.

3.3. For slow tests, trim unnecessary steps. Maybe skip retesting the homepage load if it’s already covered elsewhere.

3.4. For flakiness, dig into logs. A test failing on “add to cart” might need a smarter wait for the cart update confirmation.

3.5. Use metrics to guide you.

Rule #3. Continuous tuning sharpens your end-to-end testing best practices, making sure they scale with your app’s ambitions.

The goal of the E2E testing checklist is to give you confidence. It shows you how to prep the stage, watch the performance, and tweak test scripts on the go. Put the checklist in your toolkit.

Conclusion

We live in a world where software drives almost everything, from day-to-day shopping to accessing healthcare procedures. End-to-end testing is the methodology that can help make sure the software is reliable. Embrace end-to-end testing best practices to build good test cases. To do that:

The end-to-end testing definition is simple: ensuring the whole system works, not just the parts. But its impact is profound, reducing risks and elevating quality.

For those seeking expert support, consider DeviQA. We are a trusted software testing and QA services company. Our expertise in end-to-end testing can transform your QA process for the better.