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How To Create The Best Test Case Design To Get Maximum Test Coverage

How To Create The Best Test Case Design To Get Maximum Test Coverage

Software development is more systematic today. Organizations are seeking measures to test the effectiveness and completeness of the software to be delivered. Test coverage is considered as the most valuable of them all. Test Coverage is a technique that measures the amount of automation testing that is performed by a set of tests(or test suites). It helps not only monitor the quality of automation testing but also assist the testers to create tests that cover all the missing areas that are untested.

What is test coverage and Why is it important?

  • It gives information about the covered and uncovered area of automation testing 
  • It helps to make a decision about the quality of the product
  • It tells the QA tester which all test cases have been executed and which are not
  • Helps to create additional test cases to increase coverage
  • Identify meaningless test cases which have no role in increasing the coverage
  • Identify a quantitative measure of test coverage to ensure quality check
  • Helps to meet the exit criteria
  • Helps to keep time, scope and cost under control
  • Prevents defects at an early stage of the project lifecycle
  • Help find gaps in requirements and test cases at the unit and code level easily
  • Allows to count features and measure them against several tests

It can be done on both functional and non-functional activities but in most of the cases, the coverage calculations are based on the functional requirements only as the most important objective of an application is to do stuff what it is supposed to do.

Test coverage helps in defining certain parts of the software, to cover them with tests. Although it’s a great measuring strategy even with 100% test coverage, you can’t be certain that your application is 100% bug- free. The ideal amount of test coverage should be based on the automation testing requirements and analysis of risk.

Types of Test Coverage

There are many ways to consider test coverage. Let’s examine certain types of test coverage:

Code Coverage: It is the most popular metric for measuring test coverage for unit testing. The measurement can be broken down into different levels and depths, in terms of lines of code covered, decisions inside login constructors, among others. The criteria should be selected based on the criticality of the unit tested or how frequently it changes. Code coverage follows the white box approach and is very useful in adding new unit tests to cover code lines or branches.

Data-Oriented Coverage: It mainly emphasizes on the input and output parameters with a different spectrum of possible values they can have. In data-oriented coverage, we can go for “each choice” coverage wherein we choose each possible value at least once.

How to Calculate Test Coverage?

Test coverage is the measure of the proportion of a programming exercise during automation  testing and it gives an objective score. 

The tool measuring test coverage will monitor the code during a test suite run. The tool will attempt to check that each written line of code is called at least once during the test suite run. And this is logical – since a line that has not been called during a test suite run is effectively untested.

To calculate test coverage, you need two things:

  1. The total lines of code in the piece of software quality you are testing (X)
  2. The number of lines of code all test cases currently execute (Y)

Test Coverage % = X/Y * 100


Suppose the total number of lines of code in a piece of software is 1000 and the number of lines executed across all existing test cases is 100, then your test coverage percentage comes out to be:

(100/1000) * 100 = 10%

Code coverage can tell you how much of your code is covered by tests but it does not tell you much about the quality of the tests. When you are tracking the percentage of your code ran by your tests, the measurements of code coverage are reliable but it doesn’t tell you anything regarding the value of those tests. So code coverage on its own is not a good indicator of code quality.

A possible question would be as to what is generally accepted as sufficient test coverage when measuring the number of lines of code executed and does this metric work?

There are two parts in which we can ensure almost 100% test coverage:

  1. Good test case
  2. Adequate test coverage

A good test case captures the requirement fulfilment, you have to ensure during requirement traceability is to add good test cases, so it should be like test coverage by requirements.

Automation Testing Coverage: Few Examples

The meaning of test coverage can be different in different contexts such as product coverage, risk coverage, requirements coverage, etc. Let’s understand these with some examples.

Product Coverage: If automation testing coverage is measured in terms of the product, the main focus should be on the areas of product which have been tested and those that remain untested.


If you are testing “scissors”, you won’t be just focusing on whether it cuts a paper properly or not, but there are other aspects to look at such as User Handlingwhether the user can handle it comfortably or not.

If you ignore the other aspects of a product, you can’t claim that the automation testing coverage is complete for the product.

Cross-Browser Test Coverage

One more test coverage which is equally important is the browser’s coverage. Below are a few points we have to ensure initially:

  • Are mobile devices included in the release?
  • What are the Operating Systems, screen sizes?
  • How web applications interact with the operating systems and browsers?
  • Test environment, context?

There is one way to execute and cover the test criteria is that execute critical test cases on all browsers and operating systems and then run the less risk test cases on different browsers. In this method in the end, we don’t have any clear picture of test results but it can be improved after following multiple test cycles. But if there is limited time then maybe this methodology fails because at multiple test cases run consumes a lot of time.

There is another to do it wisely is to divide the sprint days and prioritise the browsers according to the below table:

Suite Day1 {IE, CH, FF}Day2 {IE, CH, FF}Day3{IE, CH, FF}

So through this method at the end of the sprint, you can cover each browser and cover maximum test coverage.

Requirements Coverage: If you have developed an awesome application but it’s not aligned with the customer’s requirements, then it is just crap.


If you are testing a chat application and you have covered everything from two users chatting independently to multiple users chatting in a group. But you forgot a key point mentioned in the requirement document that when two users chat independently, a video call option will be enabled.

How to Achieve Maximum Test Coverage?

  • Capture all the project related requirements at an early stage
  • Identify the critical requirements more accurately by having all the information on the differences between the current release of a product/app and the previous one to maximize positive coverage
  • Capture the critical test cases as early as possible
  • Prioritize the requirements and focus on areas which are of high importance
  • Adapt to test automation and use test management tools
  • Take an estimation effort in the execution of the test cases
  • Make your best resources work on the critical tasks and let new testers explore more from a fresh perspective
  • Include the developers as well in the process of writing automation tests
  • QAs  and BAs should perform the prioritization of the backlog tasks
  • Always maintain a checklist for all the tasks and activities
  • Interact more with your Dev team to get application behaviour insights
  • Keep track of your build cycles and bug fixes
  • Implement the continuous integration so that you can focus on better stability at the later stages as it’s done through the continuous integration for regularly integrating code changes into a shared code repository. Each commit triggers a build during which tests are run that help to identify if anything was broken by the changes.

By understanding automation testing coverage and considering these techniques and with automation as a part of the automation testing strategy, and applying long term coverage criteria, testers can maximize and optimize their test coverage over time. We need to focus on those test coverage criteria that best suit our needs. Testsigma offers comprehensive solutions that can help automate all the complex automation testing activities. Start using it today to fast track your automation testing at the speed of Agile.


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