Top 10 Reasons Why There Are Bugs in Software

Developers, project managers, and software testers work together to create various kinds of software—from mobile apps and websites to critical systems in industries like healthcare and finance. However, despite the best efforts of everyone involved, bugs and defects are an inevitable part of the development process. They can range from minor inconveniences and typos to major flaws that can leave serious impact, such as downtime, data loss, security vulnerabilities, and even loss of life.

In this blog, we will take a look at some of the reasons for bugs and defects and how to mitigate them to create high quality software.

1. Human error

Human error is one of the most common causes for software bugs and errors. We all are human and we make mistakes, including developers, testers and product managers. It is inevitable that mistakes will occur at some point in the development cycle. While with modern tools and good practices it is possible to mitigate human errors, they are still responsible for a large portion of bugs. These errors can be introduced through coding issues, logical errors or overlooking details. In addition to tight deadlines and complex tasks, long working hours, stress and fatigue, can result in bugs and issues that would normally be caught otherwise. 

Developers can make typographical mistakes that could lead to syntax errors.  Usually, they can be caught early, but if the mistakes are subtle, developers might not notice them and they can cause issues down the line. Not following consistent coding practices and guidelines, especially if there are multiple developers in the team working on the same project, can also introduce bugs. For example, one developer may validate one part of the system, while another developer does it elsewhere. This can cause issues, such as unvalidated inputs.

Humans can sometimes get overconfident, especially when working on a similar problem multiple times. Without paying attention, we might miss a detail that could potentially create an issue.

How to lower the risk of human errors?

These issues can be mitigated by pair programming and code reviews. Multiple people working on the same task, while adapting to best practices, can help catch issues before they raise any concerns. It is also important to properly manage time and workload while staying productive and avoid getting stressed and fatigued.

2. Incomplete requirements

Software development typically starts with gathering requirements. This includes the expectations, needs, and constraints of the software from the stakeholder’s perspective. At times, projects tend to be rushed and there might not be enough time to discuss set requirements in detail. This focus on speed over clarity can leave teams assuming they’ll work out the specifics later in development. When requirements are vague, incomplete, or ambiguous, developers may not have a full understanding of what they’re supposed to build. This can lead developers to make assumptions and their own interpretation of the required functionality. 

Having incomplete user stories and use cases might lead to uncovered edge cases, making it work only under ideal conditions without taking in account other possible paths. 

A lack of defined business rules can affect the functionality of systems relying on them, such as in finance. Without specifying the business rules that are applicable for the current system, such as eligibility or validation process, can lead to missed or wrongly implemented methods. This can result in software that does not meet end-user needs and can have unexpected behaviors, also missing critical functionality and potentially missing edge cases. Requirements need to be clear, understandable and detailed enough, giving measurable terms to be used as guide points when creating the asked product.

How to deal with incomplete requirements?

Avoid implementing requirements according to your own interpretation. Instead, communicate and discuss any confusing or incomplete instructions. Make sure to include key stakeholders early in the process and invest sufficient time for clarifying and exploring possible scenarios to gather more detailed and complete requirements. This allows developers to create the product that is described and desired by stakeholders. 

3. Changing requirements

One of the most significant challenges in software development is handling changing requirements. As the project goes on, stakeholders often realize that they are in need of new features or adjustments to existing functionality. Frequently shifting priorities and what needs to be done can make the development chaotic. While flexibility is important, constant or poorly managed changes can lead to multiple bugs and defects. Changing or adding more requirements by the end of development and increasing the scope can cause everyone involved to be in a rush, thus raising the risk of introducing more bugs. Frequent or last minute changes also reduce time not only for the development, but also for thorough testing. This increases the likelihood of defects getting missed and making into the product. 

How to deal with changing requirements?

If the project has constant changes in requirements, adapting to Agile methodology can help lowering risks that come with these changes, as it emphasizes flexibility while maintaining focus on delivering in short increments. This can help teams manage changes without introducing many defects and using rigorous regression testing, possibly catching any issues early.

4. Lack of communication

Effective communication is not only important in business in general but during software development as well. It is crucial, especially if there are multiple teams, stakeholders, or different locations and time zones involved. Poor communication practices or misunderstandings can lead to delays and incomplete or incorrect information getting passed on. 

Different interpretations of the same terminology or concepts can lead to conflicting implementations. This inconsistency can affect non-technical stakeholders as well, if developers and business stakeholders are not on the same page. Cultural differences in communication styles and language barriers can also be a cause of communication issues. Hesitation in asking questions for more clarification or not challenging assumptions can result in working with incomplete information. This is more common when working with international teams. 

How to improve communication?

It is important to have clear and regular communication channels for information about any issues and changes. Encouraging collaboration between developers and QA testers is key, as both work to ensure that users receive a high-quality product that meets their expectations. Constant feedback is essential for everyone involved. Involving stakeholders in the process regularly can clear up any misunderstandings and assumptions about the product. Continuously updated documentation can reduce communication gaps as well, which can also help new team members understand the work processes and features of the product. Visual aids, diagrams, and simplified language can ease up communication and make bug reports clearer for the developers. 

5. Complexity of code

As the software product grows in size throughout the development cycle, so does its complexity. Complex code can be difficult to understand, maintain, and test, which can lead to an increased risk of bugs and defects. The complexity can arise from the system architecture, intricate logic, or excessive interdependencies, introducing challenges that can also lead to more errors.

The architecture of the product plays a major role in its complexity. Having poorly designed architecture can cause multiple issues in the long term. It can raise difficulties in building more features, as well as extending or modifying existing ones.

Code that is not modular and reusable will lead to unnecessary complexity. It can make developers use the same lines of code in multiple places, which will add difficulty when it is necessary to make updates and bug fixes, causing issues that could have been avoided.

Spaghetti code is also a cause of the code being too complex and not understandable. The term "spaghetti code" refers to code that is poorly structured. It is tangled and has unorganized logic, which makes it hard to follow. Spaghetti code often arises from quick fixes, lack of planning, or adding too many features without proper refactoring. This chaotic structure makes it difficult to predict the impact of changes, increasing the chance that modifying one part of the code will unintentionally affect other areas. Spaghetti code also worsens its readability, which makes it harder for other developers on the team or future developers to understand it.

How to work with complex code?

Following best practices will help maintain complex code better. This can be achieved by pair programming, adhering to coding standards, appropriately using design patterns, ensuring that code is clean, well structured and documented. Without consistent practices, developers will struggle to maintain already existing code and add more things to it.

You may also be interested in: Issue Reproduction—Why Reproducing Bugs Matters.

6. Poor documentation

Documentation is essential and it serves as a backbone of communication in any software development. It ensures that developers and testers, as well future maintainers understand how the software product is designed, how it functions, and how to interact with it. 

In fast-paced projects, it is easy for documentation to fall behind. Outdated documentation can mislead both developers and testers. Both developers and testers may introduce defects or overlook them, with testers also at risk of finding false positives. 

While documentation needs to be detailed and up-to-date as much as possible, it also needs to be accessible and understandable to the target audience. Overly complex documentation can push away developers and testers who do not have as deep technical knowledge as the ones who wrote this documentation. If developers and testers cannot understand the documentation, then they might make more mistakes along the way, thus causing or missing defects in the product.

How to avoid issues due to poor documentation?

Documentation should be up to date, from requirements to any technical specifications. Take time to review documentation during major updates or new feature additions. Making documentation clear, accessible, and inclusive of main use cases and edge cases helps developers and testers better understand the product’s core functionality, reducing potential defects. Comments in the code can help other developers in the team, or any future developers that might work with the same code, understand what has been implemented and how it works.

7. Inadequate testing

Testing is a crucial part of any software development to ensure that everything is working as intended, user requirements are met, and the risk of bugs escaping in production is kept to a minimum. Not only developers, but testers can also make mistakes or choose inadequate testing approaches.

In fast-paced projects, time is of the essence, which can cause testing to be rushed. Rushed testing can cause defects and bugs to be missed, when normally with sufficient time they would be caught.

While functional testing ensures that a product works as intended in normal conditions, it is important to include other testing processes. One of the examples is performance and load testing. They identify how the product works under heavy usage and can help find issues related to latency and resource usage. If there are no performance and load tests, then issues related to these will be missed. Security testing, for example, is important to find any vulnerabilities and exploits in the system. Without it, the system is prone to malicious users and data leaks. 

Lack of automation can also be a cause of introducing defects to the product. Manual testing is prone to human error, especially when testing needs to be done repetitively throughout multiple iterations. Without automation tests, repetitive tests might get rushed or skipped altogether.

How to avoid inadequate testing?

Testing needs to be aligned with user expectations and product requirements. Creating a test plan is essential for adequate testing, as it can help to coordinate the testing process. While functional testing is important, it is also important to not forget about other kinds of testing, such as performance and load testing, and security testing. Choosing an appropriate testing environment, devices and approaches are crucial in finding as many defects as possible.

8. Time constraints

Time constraints are one of the most common sources of pressure in software development. At times, deadlines can be tight due to unrealistic timelines set by management, stakeholder expectations or external factors. Development teams often get pressured to deliver features, mostly complex ones, in a short period of time. For this reason, they have to find compromises and have to accommodate to finish their product on time. 

These compromises may include rushing through critical phases of the development process, such as design, coding, and quality assurance. Teams might also decide to delay non-critical bug fixes. While this can seem like a reasonable trade-off, in the long term, it can result in technical debt and accumulate more in time. Cutting corners of functionality can also be a result of time constraints. The team might prioritize the minimum viable version of the system due to time constraints. This solution might skip or poorly implement error and edge case handling and non-critical functionality. This can increase the likelihood of bugs and defects, which can lead to reduced quality, incomplete development, and inadequate testing.

How to mitigate issues in time constraints?

The most obvious thing would be setting realistic deadlines to ensure that everything needed can be implemented and thoroughly tested. Using Agile methodologies can also help team work in short increments to maintain quality. Delivering in increments and avoiding leaving implementations and fixes for later can help minimize risks along the way and save up time.

9. Technical debt

Rather than taking the time to implement the best possible solution using advanced or expensive methods, choosing a faster, cheaper, and simpler solution can be mesmerizing. However, choosing the simple path can be less optimal in the long run, which can cause future inefficiencies, additional rework, and cost. This technical debt can be the result of compromising during tight deadlines or by accommodating with limited resources. While the approach might give immediate benefits, it can be hurtful for the project as time goes by, leading to long-term problems, including software bugs, performance issues, and higher maintenance costs. 

Technical debt can also waste time that is most likely already limited and cannot be spared, so going back and trying to mitigate issues that stem from it can leave a negative impact. That includes avoiding or postponing code refactoring and cleanup, which will make it harder to maintain and modify, causing issues that stem from code complexity.

How to work with technical debt?

One of the first steps to work with technical debt is recognizing it. By figuring out where the developed product is falling behind, you can decide the next course of action. Communication with stakeholders about the impacts of current technical debt can help in allocating time and resources to keeping technical debt to minimum. Regular refactoring and having code clean can reduce the risk of issues caused by technical debt. Using automated testing, including unit tests and integration tests, can help catch bugs that arise from technical debt.

10. Environmental factors

Many applications today are developed in virtualized or cloud-based environments and then they are deployed to their respective target platform. External conditions and settings in which software is developed, tested, and deployed can have a significant impact on the performance, stability, and reliability of the software. Differences in hardware, operating systems, configuration, and network conditions can be a cause of different kinds of issues. Various types of CPUs, storage systems, and other kinds of hardware configurations can cause bugs that appear in some hardware combinations, but not in others. 

Operating systems have their own way of managing permissions, file systems, or using different kinds of libraries. One operating system can run the created software with no issues, while another might cause problems due to incompatibility with certain modules in the set environment. 

The security and permission structure of the environment can affect how the software operates. One environment could have tighter security policies and more restrictions to prevent users from doing certain actions, while other environments might not be as strict, allowing users to do something that would not be possible elsewhere. That is why it is important to do testing that takes into consideration different platforms, devices, and other factors that could cause software to behave differently.

How to consider different environmental factors?

Using tool containers, such as Docker, can help ensure that software behaves the same regardless of where it’s running. Testing software on different sets of devices with different hardware and operating systems can help to cover compatibility issues. Trying out different kinds of permission configurations can help to figure out issues due to insufficient permission settings or policy violations in one environment or another. Simulating real-life scenarios, such as different network conditions, makes sure that end users can use the software at its best in their own environment.

Final thoughts

While bugs and defects are inevitable and a natural part of the development process, it is important to know and understand their causes. From human errors and incomplete requirements to inadequate testing and environmental factors, the reasons for bugs and defects are vast and diverse. Figuring out where bugs and defects stem from can tremendously help ensure delivering good quality products. Using different kinds of strategies, such as communication, proper planning, maintaining documentation, and recognizing target environment issues can help everyone involved to proactively avoid and minimize issues early.

At TestDevLab, we know that bugs and defects are part of the development journey. But understanding their causes is key to delivering high-quality products. Contact us today to discover how we can elevate your QA processes and enhance your product’s quality.