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What is Test Coverage?

Having a bug-free application is the dream that every developer and tester chases. You may have encountered numerous occasions where unsightly bugs were discovered despite the code being written exactly as per requirement. These issues include performance-related issues or even simply failing to identify real-world use cases. Having ways to ensure every part of the application gets tested before it is made available to the customer is precisely what test coverage is for. Read on for a deeper understanding of this concept.

What is test coverage?

In software testing, code coverage measures how many lines of code are tested (covered) by automated tests. For example, you have a total of 1000 lines of code, out of which 700 are covered with tests. This is a quantitative test of your code. Since tests are mapped to source code, code coverage can be considered a white-box testing technique.

“Test coverage,” on the other hand, has no single clear definition. Martin Fowler, ThoughtWorks, and Wikipedia say it is the same as code coverage.

The most common definition of test coverage is that it is a qualitative measure of whether all the features in your application are covered with tests. This means that with test coverage, one is not to bother with the internal workings of the application, but rather focus on how well the different components of the application are functioning.

For example, if your application has a cataloging system, then some of the test scenarios would include ensuring that all items are displayed properly, are searchable, and can be added to the cart. Over here, you will not be worrying about which code method is being summoned to perform each operation, or how many lines of code are being executed for your test case. Thus we see that test coverage is a black-box approach to ensure software quality – since you are only concerned with the output rather than how or what is written in the code.

Different types of test coverage

Ensuring that your application is tested holistically can seem like a daunting task. To provide solid test coverage, you will need to view your application from different angles to cover maximum ground. Below are some points to consider when undertaking this activity.

Product coverage:
This is the top view. Look at your application as a collection of different features or entities. Each of them together forms the final product. This means that you need to write test cases for all these various features while considering
  • Positive test cases
  • Negative test cases
  • User-centric paths

For example, let’s talk about an e-commerce website. You can say that at a high level, the website comprises a login module, inventory, catalog module, cart module, and checkout module. So you will be writing test cases for each of these modules. If we look at the checkout module, then it could have test cases like – Am I being redirected to the checkout page? Am I able to make a payment? Am I seeing a success message? If the payment fails, is there a failure message? On failure, does the cart content remain the same? On success, does the cart content update?

Your aim should be to test each module of your product.

Requirement coverage:
New requirements come into the picture based on market trends, customer feedback, and demand. These requirements are essentially user needs. Quite often, during the development cycle or even in the testing phase, you may need to pay extra attention to certain aspects of the requirements.

Consider the above e-commerce website as an example. Let us say that a new requirement came in asking for a chat application within the website so buyers can talk to the seller about various items. However, while testing, testers observed that when suppliers closed all browser tabs, they were logged out of their accounts but were still represented as active on chat. Such issues can lead to potential customer dissatisfaction and confusion.

Risk coverage:
Assessing risk associated with any kind of development is an essential part of quality assurance. Along those lines, we can say that testing risky scenarios is a good practice.

Compatibility coverage:
Ensuring that the application performs well across platforms is a big task. Testing with different hardware configurations, network conditions, cross-browser testing, OS compatibility, and mobile testing are some of the categories that come under verifying applications’ compatibility.

Boundary value coverage:
These scenarios are meant to include those situations where the application is not supposed to accept values outside of a given range. For example, if the catalog lets you choose negative values for item count, that is a boundary-type issue.

Benefits of test coverage

Test coverage can be viewed as a proactive step for ensuring high-quality products. Some of the benefits of having test coverage for your application are as follows.

Smoother test cycles:
Having good test coverage helps streamline the testing process. You can utilize automation testing as well to target areas that need to be tested after every release. Strategizing test case prioritization and test suite minimization helps improve test coverage, leading to efficient test cycles.

Early detection of issues:
You can ensure maximum coverage with a well-maintained test suite and test coverage plan. This will help you identify problems in advance.

Removing redundant test cases:
With test coverage, you can identify and eliminate those test cases that are no longer useful to your project. Having lighter test suites is ideal for periodic test suite maintenance and regular testing.

Higher ROI:
Since test coverage helps catch issues early and streamline the testing process, the chances of customers receiving a good quality application are higher. This leads to happier customers, higher customer satisfaction, and better sales.

Tips to improve test coverage

Since test coverage is a qualitative process, it varies from application to application. Based on your application, you need to chart a strategy for testing. Below are some ways to achieve good-quality test cases.

Use automation to build strong test cases:
Automation is a great ally when it comes to testing. Scenarios that need to be tested repeatedly can be automated, helping to save time and resources. Choosing the right user-friendly tool for this task is imperative.

Gather data:
Being in touch with market trends: how your application is faring, critical issues that have arisen, and customer feedback are ways to ensure that you cover all crucial areas in your application. For example, if your e-commerce website had a major bug about cart count not getting updated once items are added, you need to make sure that this scenario will be added to your regression test suite.

Devise robust test suites:
Keep your test suites lightweight and dynamic. Be sure to avoid redundancy in your test suites so that execution and reporting results are more accessible.

Conclusion

When it comes to test coverage, there is no one-size-fits-all approach. First, when talking about “test coverage,” always clarify the phrase’s definition to ensure everyone is on the same page. You can devise a strategy that ensures maximum coverage based on your application and needs. Though this may seem like a lot of work, remember that having a good foundation for testing will pay off in the long run.

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