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The Challenges of Achieving 100% Test Coverage in Self-Service, Multi-Platform Monolith Applications

Dan Kushner
4 min readNov 22, 2023

The Illusion of Complete Testing

The reality of “We Can’t Test All The Paths”

In the complex world of software development, particularly for self-service, multi-platform monolith applications with a multitude of features, the idea of achieving 100% test coverage is more of a myth than a reality. Why? Because testing every conceivable path in an application is a near-impossible task.

You Can’t Test a Program Completely

Testing a program completely would mean covering every line, branch, and potential error, a goal that quickly becomes impractical in the face of intricate application architectures. Even with 100% line or branch coverage, the assurance of having tested for every possible error remains unattainable.

Defining “Coverage”

Coverage, in testing terms, measures the extent of testing done of a certain type. It’s a metric for your effort to detect potential errors. However, this metric is not an absolute indicator of the thoroughness or effectiveness of the testing process.

So What is Coverage?

  • 100% line coverage implies testing every bug revealed by executing a line of code.
  • 100% branch coverage aims at finding every error shown by testing each branch.
  • But 100% overall coverage? That’s an unachievable ideal.

Implications and Conclusions

The core problem with testing lies in its inherent limitation — we can only run a fraction of all possible tests. Test planning, therefore, becomes a development of a sampling strategy, governed by practical heuristics rather than rigid standards.

Common Challenges in Testing Self-Service, Multi-Platform, Monolith Applications Challenge

  1. Infinite Possibilities of User Inputs and Interactions

Real-world applications often have a wide range of inputs and user interactions, making it virtually impossible to test every combination, especially in complex applications.

2. Multi-Platform Compatibility

Different platforms with their unique behaviors add layers of complexity.

3. Resource Constraints

Achieving 100% test coverage would require immense resources such as time, manpower, and costs. The effort to cover every path and scenario could be prohibitively expensive and outweigh the benefits.

4. Diminishing Returns

Beyond a certain point, the effort to increase test coverage yields diminishing returns. Focusing on edge cases might not add significant value compared to covering critical and common use cases.

5. Changing Requirements and Code

In agile and iterative development environments, frequent changes in application code and requirements make maintaining 100% coverage a continuous and often unattainable challenge.

6. Complex Business Logic and Scenarios

Applications with complex business logic or operating in unpredictable environments present scenarios that are difficult to anticipate and comprehensively test.

7. Third-Party Integrations and External Dependencies

Testing all interactions with third-party services, APIs, or external systems is challenging, especially under every possible condition, due to limited control over these external factors.

8. Hidden or Unreachable Code

Some parts of the code may be rarely used or only activated under specific conditions, making them hard to reproduce and test in a standard environment.

9. Non-Functional Requirements

Achieving 100% coverage in non-functional aspects like performance, security, and usability is challenging due to their subjective nature and external influences.

10. User Experience and Usability

Testing for user experience and usability aspects often requires qualitative analysis, which cannot always be quantified in terms of coverage.

And more…

These challenges underscore the need for a strategic testing approach that prioritizes critical functionalities and user scenarios over an unattainable 100% coverage goal.

Addressing the Challenges

Employing a mix of manual and automated testing, along with specialized techniques like performance and security testing, is crucial. Continuous integration and deployment (CI/CD) practices are also vital to integrate testing seamlessly throughout the development lifecycle.

The Pragmatic Approach to Testing

Instead of chasing the elusive 100% coverage, it’s more practical to aim for meaningful coverage that focuses on critical functionalities and high-impact areas. This approach balances thorough testing with the constraints of real-world development, ensuring quality without getting bogged down in impractical goals.

Conclusion

In essence, striving for 100% test coverage in self-service, multi-platform monolith applications with many features is more a pursuit of an ideal than a practical goal. Understanding the limitations and focusing on a strategic, risk-based testing approach is the key to efficient and effective software testing in such complex environments.

References:

Testing
QA

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Dan Kushner

Written by Dan Kushner

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