Beyond Coding: Post-Release Quality with Unit Tests and Code Reviews

By Daniel Nguyen, Software Engineer at Groove Technology

When I first started as a developer, my focus was all about writing code and delivering features on time. As long as the functionality worked and passed the initial tests, I felt like the job was done. However, as I gained more experience and had to deal with post-release issues, I realized that coding is just one piece of the puzzle. The real challenge comes after the code is written—ensuring that it continues to perform and doesn’t break things down the line.

In my daily work, ensuring post-release quality is just as important as delivering features. Two practices that have helped me maintain this quality are unit testing and code reviews. They’ve drastically reduced the number of bugs that slip into production and minimized client complaints. In fact, since my team fully adopted these practices, we’ve seen a 30% reduction in post-release bugs and client support tickets.

Let me walk you through how I approach both unit testing and code reviews in my workflow, what I’ve learned along the way, and how these practices can make a real difference in delivering reliable, high-quality software.

01. Why Unit Testing Isn’t Optional (At Least Not for Me)

Unit testing might sound like an extra step that just adds time to development, but for me, it’s become an essential part of the process. I use XUnit for unit testing, particularly in .NET projects, because it ensures that every function or module I write behaves as it’s supposed to, in isolation. The purpose here isn’t to test everything; it’s to make sure that each piece of the system works on its own before it integrates with other parts.

In one of our recent projects, unit testing saved us from what could have been a post-release disaster. We had a function for calculating discounts, and a small change to the logic during a refactor could have introduced a bug that affected pricing for thousands of users. Luckily, our unit tests caught it long before it reached production.

02. How I Write Unit Tests That Actually Matter

The key to writing useful unit tests is focusing on what matters. I don’t try to test every trivial function—just the parts that deal with business logic or critical calculations. For example, if you have a function that handles user authentication or payment processing, that’s where your testing effort should go.

Here’s a real-world example of an XUnit test I wrote for a function that calculates the total price of an order:

This simple test checks that after applying a 10% discount, the total price reflects the discount properly. If the logic in GetTotalPrice changes down the road and breaks, this test will catch it.

03. Advantages of Unit Testing: The Stuff You Don’t See Immediately

3.1 Catching Bugs Early and Often

Bugs caught early are far less expensive and time-consuming to fix than those discovered after a release. With unit tests, I’m catching potential issues as I write code, not weeks later when users start reporting problems. In one of our projects, we had an edge case where a specific input format caused our date parser to fail. A simple unit test caught the issue early, preventing hours of troubleshooting down the line.

3.2 Confidence to Refactor

Refactoring is something I’ve grown to love—cleaning up code and making it more efficient. But it’s risky if you don’t have proper tests in place. Unit tests give me the confidence to refactor without worrying that I’ll break something elsewhere in the system. When I’ve got a good suite of tests, I can move things around freely, knowing that if something does break, my tests will catch it.

3.3 Documentation for Code Behavior

Good unit tests don’t just verify functionality—they also act as living documentation. Well-written tests show exactly how a function is supposed to behave under different conditions. This is particularly helpful for new developers joining the project, as they can look at the tests to understand the code’s expected behavior without needing to read long, outdated documentation.

04. Challenges with Unit Testing: Not Always Smooth Sailing

4.1 Time-Intensive for Complex Systems

For larger, more complex systems, writing unit tests for every possible case can feel overwhelming. When deadlines are tight, spending time on writing tests feels like a luxury, even though I know it’s necessary. It’s always a balance between speed and long-term stability.

4.2 Keeping Tests Relevant

Maintaining unit tests as the system evolves is a pain point. If a function’s logic changes, you have to update or rewrite the tests, or they’ll become useless. If you’re not disciplined about maintaining your tests, they can give a false sense of security.

4.3 False Sense of  Security

Unit tests are great at testing individual components, but they don’t guarantee that those components will work well together. Relying too much on unit tests can give a false sense of security, leading developers to believe that if their unit tests pass, the system as a whole is stable. That’s why it’s essential to complement unit tests with integration and system tests.

Watch this short video where I talk about the real-world impact of unit testing in my daily workflow.

05. Why Code Reviews Are Non-Negotiable

Unit tests catch technical bugs, but there’s a lot that tests can’t catch—like bad design decisions, inefficient code, or potential security issues. That’s where code reviews come in. Code reviews aren’t just about finding mistakes; they’re about improving the overall quality of the code and sharing knowledge among the team.

Every time I finish a piece of functionality, I create a Pull Request (PR) for the team to review. This isn’t just a formality—it’s a critical part of our workflow. Here’s why:

5.1 Catching What Tests Can’t

A unit test might check whether a function returns the right output, but a reviewer might spot something more subtle—like a performance issue or an opportunity to simplify the code. For instance, in one review, a colleague pointed out that I was using a nested loop that could be replaced with a more efficient algorithm. Tests would never have caught that.

5.2 Fostering Collaboration and Knowledge Sharing

Through code reviews, I’ve learned so much from my colleagues. It’s a two-way street—I share my perspective on their code, and they do the same for mine. This knowledge-sharing builds a stronger team, and over time, it makes everyone a better developer. I remember one particular review where a senior engineer pointed out a potential security vulnerability I hadn’t considered. That feedback saved us from what could have been a significant issue post-release.

5.3 Enforcing Coding Standards

Code reviews help enforce coding standards within a team. They ensure that everyone is following the same rules and writing code in a way that’s consistent and easy to understand. This makes the codebase more maintainable in the long run, reducing the chances of someone introducing bugs because they didn’t understand how something was written.

06. Code Review Challenges: Let’s Be Real

6.1 Time and Effort

Like unit tests, code reviews take time. If a PR is too large, it can be overwhelming for the reviewer. One of the biggest lessons I’ve learned is to keep PRs small and focused. This not only makes it easier for the reviewer but also speeds up the process.

6.2 Review Fatigue

In busy projects, the constant cycle of reviewing code can lead to burnout. I’ve been there—rushing through a review because I was juggling other tasks, only to miss something important. To avoid this, we’ve adopted a policy of assigning reviews in a balanced way so that no one gets overloaded.

6.3 Inconsistent Reviews

The quality of a code review can vary depending on the experience and attention of the reviewer. Some reviews are incredibly thorough, while others may gloss over critical issues. Over time, I’ve realized that it’s essential to establish review guidelines within the team to ensure consistency in the process.

07. Unit Tests and Code Reviews: Why They’re a Powerful Duo

In my experience, unit testing and code reviews aren’t standalone practices—they’re complementary. Unit tests ensure that individual components work correctly, while code reviews catch broader issues like design flaws and inefficiencies. Together, they form a solid foundation for maintaining post-release quality.

Here’s how we integrate the two in our process:

• Before Submitting a PR: I always write unit tests for the functionality I’m submitting. This ensures that my code is technically sound before someone else looks at it.
• During Code Reviews: Reviewers not only look at the code but also at the unit tests. Are the tests comprehensive? Do they cover edge cases? This ensures that tests aren’t just written for the sake of it—they’re actually meaningful.

08. Lessons Learned and Best Practices

Over the years, I’ve developed a deeper understanding of how unit testing and code reviews fit into the bigger picture of software development. Below are some of the key lessons I’ve learned along the way, with practical insights you can apply to your own workflow.

8.1 Automate Your Unit Tests in CI

One of the biggest shifts in our team’s efficiency came when we integrated unit testing directly into our Continuous Integration (CI) pipeline. By doing this, every time code is pushed, it automatically runs all existing tests before merging into the main branch. This has been a game changer for us because it prevents broken code from being merged, saving hours of troubleshooting later on.

Here’s what I recommend:

• Set up your CI to run unit tests as a mandatory step before any pull request can be merged. This adds a level of safety and reduces manual testing efforts.
• Use test coverage reports to ensure you’re not just writing tests for the sake of it, but actually covering critical paths. However, don’t aim for 100% coverage—focus on areas of high importance, like core business logic.

8.2 Keep Pull Requests Small and Focused

One thing I’ve learned through many long, painful code reviews is the importance of keeping pull requests (PRs) small and focused. Large PRs are difficult to review properly, and critical issues often get overlooked. When a PR focuses on a single feature or a small set of changes, the reviewer can provide more thorough feedback.

Here’s how I’ve handled it:

• Break down larger tasks into smaller, more manageable PRs. For example, if you're implementing a new feature that involves several modules, submit one PR per module or functionality.
• This not only helps the reviewer focus on the quality of the code but also ensures that if issues arise, they are isolated to a smaller change set, making debugging faster.

8.3 Write Tests That Add Real Value

One of the hardest parts of unit testing is finding the balance between testing enough and over-testing. I’ve seen developers write exhaustive tests for trivial functions that add little value, while neglecting complex business logic that is far more critical.

The approach I follow is:

• Focus on core functionality and critical paths in your application, like business logic, security-related code, and high-risk areas. I prioritize writing tests that ensure the most important parts of the system work under a variety of conditions.
• Keep the tests maintainable. Write clean, concise tests so that when the code changes, the tests are easy to update. Tests that are too brittle or too specific become a maintenance burden.

8.4 Use Code Reviews for More Than Just Finding Bugs

Code reviews are about far more than just catching bugs—they’re about improving the design, ensuring performance is optimal, and helping the team write better code over time. Through PR reviews, I’ve received invaluable feedback that helped me optimize performance or simplify a complex function, which unit tests alone wouldn’t have caught.

Here’s what I focus on during code reviews:

• Look for code readability and maintainability. Is the code easy to understand? Could someone new to the project pick it up quickly?
• Ensure the architecture makes sense. Sometimes, developers will create overly complicated solutions when a simpler one would do. Code reviews are an opportunity to challenge design decisions and suggest improvements.

8.5 Foster a Culture of Constructive Feedback

One of the most valuable aspects of code reviews is the feedback loop they create within the team. However, I’ve learned that the way feedback is delivered matters just as much as the content. Constructive feedback helps improve the code without discouraging the developer.

My approach:

• Focus on suggestions rather than criticisms. Instead of saying, “This is wrong,” I might say, “Have you considered using this approach? It might simplify things.”
• Encourage dialogue in reviews. Sometimes I learn new techniques from junior developers who bring fresh perspectives or newer practices.

09. Final Thoughts: Ensuring Quality Long After the Code is Written

Writing code is just the beginning. Ensuring post-release quality takes continuous effort, and the combination of unit tests and code reviews is a powerful way to achieve that. For me, these practices have not only reduced the number of post-release bugs but also made me a better developer. They force me to think ahead and ensure that what we build today will still work tomorrow.

Daniel Nguyen is a Software Engineer at Groove Technology, focused on ensuring high-quality software through unit testing and collaborative code reviews.