What is Functional Testing?
Software testing is the process of evaluating the functionality of a
Functional testing is the process through which QAs determine if a
piece of software is acting in accordance with predetermined
requirements. It uses black-box testing techniques, in which the
tester does not know the internal system logic. Functional testing
is only concerned with validating if a system works as intended.
This article will lay out a thorough description of functional
testing, its types, techniques, and examples to clarify its nuances.
Types of Functional Testing
1. Unit Testing:
This is performed by developers who write
scripts that test if individual components/units of an application
match the requirements. This usually involves writing tests that
call the methods in each unit and validate them when they return
values that match the requirements.
In unit testing, code
coverage is mandatory. Ensure that test cases exist to cover the
- Line coverage
- Code path coverage
- Method coverage
2. Smoke Testing: This is done after the release of each build
that software stability is intact and not facing any anomalies.
Smoke testing ensures the appropriate and consistent functioning of
the basic functionalities and the important features. This also
ascertains the absence of show stopper bugs in the release done. The
decision on proceeding with further testing is made based on the
outcome of smoke testing. Ensure basic functionality/user journey
works and there are no show stopper bugs present.
3. Sanity Testing: Usually done after smoke testing, this is
run to verify that every major functionality of an application is
working perfectly, both by itself and in combination with other
elements. Sanity testing is a subset of regression testing. This
also checks the proper working of new functionality added to an
4. Regression Testing: This test ensures that changes to the
codebase (new code, debugging strategies, etc.) do not disrupt the
already existing functions or trigger some instability. Complete end
to end functionality of the application software once the new
feature or change has been included in it gets tested here.
5. Integration Testing: Once regression testing is done on
individual modules of the application software, integration testing
ensures that all the modules are integrated properly, that is, all
the modules work fine and in proper sequence when used combinedly
without breaking the product. If a system requires multiple
functional modules to work effectively, integration testing is done
to ensure that individual modules work as expected when operating in
combination with each other. It validates that the end-to-end
outcome of the system meets these necessary standards.
6. Beta/ Usability Testing: In this stage, volunteers or a
limited set of users for whom the new feature or changes made in the
application software have been enabled for usage will test the
product in a production environment. This stage is necessary to
gauge how comfortable a customer is with the interface. Their
feedback is taken for implementing further improvements to the code.
Process Workflow for Functional Testing
The overview of a functional test includes the following steps:
1. Create input values with boundary conditions in mind.
2. Execute test cases with defined test steps.
3. Compare actual and expected output.
Generally, functional testing in detail follows the steps below:
- Determine which functionality of the product needs to be tested.
This can vary from testing main functions, messages, error
conditions and/or product usability.
- Create input data for functionalities to be tested according to
specified requirements with boundary conditions.
- Determine acceptable output parameters according to specified
- Compare actual output from the test with the predetermined
values. This reveals if the system is working as expected.
Why automate Functional Tests?
Automation can certainly reduce time, effort and cost involved in
executing functional tests. Initially, Return on Investments is
higher. Once we get better coverage it will drastically reduce the
manual efforts and produce highly accurate results in less amount of
time. Human error can also be minimised, preventing bugs from
slipping past the test phase based on the automation coverage.
However, increased automation means that QAs need to develop test
cases for each test. Naturally, formulating the right test case is
pivotal, along with identifying the right automation tool for the
What to look for in the right automation
The tool should support all the modes(web or UI or
mobile or all) and functionality (if any complex UI patterns are
involved) of the product.
The tool must be easy to use, especially for all
members of your QA team.
It must be seamlessly operational across different
a. For example, ask yourself: Can you create test scripts
on one OS and run them on another? Do you need UI automation, CLI
automation, mobile app automation, or all of them?
It must provide features specific to your team’s
a. For instance, if certain team members are not comfortable with a
certain scripting language, the tool should support conversion to
other script languages that they may be better versed in. Similarly,
if you need specific reporting and logging or automated build tests,
the tool must be able to provide the same.
In case of changes to the UI, the tool must support the
reusability of test cases.
Best Practices for Automated Functional
Pick the right test cases: It is important to
intelligently select the test cases that you will automate..
Automate the following kinds of tests:
a. Tests that need to run repeatedly/frequently.
b. Same tests with different data.
c. P1, P2 test cases which consume much time and effort.
d. Tests that are prone to human error.
e .Same tests in different OS, browsers, devices, etc.
Dedicated Automation Team: Automation requires
time, effort and most importantly, a certain measure of
specialised knowledge and skill-set. Not every member of your QA
might be good at writing automation scripts or know how to
handle automation tools. Before deploying automated tests,
analyse the various skill and experience levels of your QAs. It
is best to allocate automation tasks to those who are equipped
to accomplish them.
Data-Driven Tests: Automated test cases that
require multiple data sets should be written in such a way that
they are reusable. For this, the data can be written in sources
such as XML/JSON files, text or property files or read from a
database. Creating a structure for automation data makes the
framework easier to maintain. It also enables more effective
usage of existing test scripts.
Be on the lookout for breaks in tests: Your test
cases and chosen automation tool must adapt to potential UI
changes. Take an example in which an earlier version of Selenium
used a location to identify page elements. Now, if the UI
changes and those elements are no longer at those locations, it
can lead to test failures across the board. Thus, consider
writing test cases that enact minimal change in the event of UI
Test frequently: Prepare a basic automation test
bucket, and strategize for frequent execution of this bucket.
With this, QAs can enhance the test automation framework to make
it more robust. Needless to say, this practice also helps to
identify more bugs.