People sometimes use the term Test coverage and Code coverage in the wrong way, confusing terms when they are two different things. Both of them are used to measure the efficiency and efficacy of the code but not always clear for development and testing teams. Code coverage is the evaluation of the code that we are going to execute and test coverage is a measure of the features tested that are covered by the test.
While Code coverage is a quantitative measure of the effectiveness of code, test coverage is a qualitative measure. The objective of both coverages remains to obtain metrics to know the quality of our application code. These metrics are important for the development team to fix any found error and increase the quality of the application. Let’s see each one independently.
What is Test Coverage?
Test coverage is a test type to ensure the quality of a product or an application that involves Software Requirements Specifications (SRS), Functional Requirements Specifications (FRS) and User Requirements Specifications (URS). Some ways to perform the test coverage are:
- Unit testing
- Functional testing
- Integration testing
- Acceptance testing
Let’s see some of the test coverage techniques: Product coverage, Risk coverage, Requirements coverage, Boundary values coverage and Compatibility coverage.
- Product coverage:
Product coverage simply means that we need to perform testing from a product perspective. We must answer the question: Which areas of the product have we tested?
- Risk coverage:
As its name suggests, it involves all the risk to an application and testing them thoroughly. As a summary, consist of listing all the risks and making sure that they are mitigated by tests.
- Requirements coverage:
Maybe the most important of the test coverage techniques. To be honest, if we develop an application that might work well but does not meet the user’s requirements… we have an useless application. We must take the requirements list into account when we create the test plan. It’s essential and it helps to ensure that the requirements are fully covered.
- Boundary values coverage:
This technique consists of ensuring that the boundaries are tested across the application. Imagine that we have a feature that can take numbers as input but only accepts numbers from 0 to 10, both of them inclusive. In similar scenarios like this, to ensure that they are properly tested, we should test the boundary, the below and the above the boundary.
- Compatibility coverage:
We must make sure that our tests cover our application across different browsers, devices and operating systems. Obviously, we can not and it’s not needed, to test across all the possible combinations, because we must spend a lot of time doing that and the benefits do not compensate for it. We must perform an analysis of which browsers, devices and operating systems are more used to cover them.
What is Code Coverage?
As we said before, Code coverage is the metric that describes how effective and efficient the code of our application is. With the continuous development of the application and the bug fixing, the test codes need maintenance correspondingly and of course, the addition of new tests to cover the new features. Exist different types of code coverage in software testing and it is important to know each one of them that aims for different part of our code:
- Branch coverage:
Is a White box testing method in which every outcome from statements or loops is tested. The purpose of this method is to ensure that each decision condition from every branch is executed at least once. This helps to measure the code segments and to find out sections without branches.
- Function coverage:
Similar to branch coverage, the function coverage makes the execution of each function easier while performing code coverage. Function coverage checks if different types of arguments are passed onto the function to verify the efficient functionality.
- Condition coverage:
This coverage technique tests the conditions that are present in our code and is tested at least once. This means that each individual condition is one time true and false.
- Statement coverage: Statement coverage is one of the simplest coverage techniques. Perform the test executing all the statements at least once in the source code. Using this technique we can check what the source code is expected to do and what it should not.
- Loop coverage: This way checks if the loops are working properly or not. The loop coverage can change depending on the people using it for different applications or loop conditions. It’s more common to use the Loop coverage as validating the loop entering once while for the others it’s more than one time.
So now that we have a clear definition of both concepts, which one should we choose?
This is a heavy cross to bear, test coverage vs code coverage. Which one and why? Both of these are completely different and it’s hard to justify to designate between the two. Code coverage is a white-box testing technique and gives us a quantitative measure while on the other hand, test coverage is black-box testing and gives us a qualitative measure.
Neither of them are perfect; depending on our business requirements and the software application we could choose one but in the majority of the cases, both test coverage and code coverage are, and must be, used.