What Is Meant By Unit Testing?

Unit Testing in Software Testing

What is Unit Testing in Software Testing?

UNIT TESTING is a software testing process that examines individual software units or individual components. The aim is to ensure that each unit of software code works as its supposed to . Developers carry out unit testing all around an application’s development (coding) process. Unit tests isolate a part of code and ensure that it is correct. An individual function, method, process, module, or object might be considered a unit.

Unit testing is the first level of development testing performed before integration testing in the V Model, STLC, and SDLC. Unit testing is a kind of WhiteBox testing done by the developer. However, due to time constraints or developers’ reluctance to test in the real world, QA engineers also perform unit testing (performance testing).

In this article:

  1. Why Unit Testing?
  2. What Do Unit Tests Look Like?
  3. Who Should Create The Unit Test Then?
  4. How to do Unit Testing
  5. Unit Testing Techniques
  6. Unit Test Example
  7. Unit Testing Tools
  8. Test-Driven Development (TDD) & Unit Testing
  9. Unit Testing Myth
  10. Unit Testing Advantages
  11. Unit Testing Disadvantages
  12. Unit Testing Best Practices
  13. Summary

Why Unit Testing?

Unit Testing

Since software developers often want to save time by implementing minimum unit testing, this is a misconception because insufficient unit testing leads to high costs for defect correction during Integration Testing, Beta Testing, and even System Testing after the program has been constructed. It helps to save money and time in the long run if proper unit testing is done early in the development process.

The following are the key reasons to perform unit testing in software engineering:

  • Unit tests save money and time by catching bugs early in the development cycle.
  • Good unit tests serve as project documentation.
  • It helps developers in understanding the testing code base and allows them to make quick adjustments.
  • Unit tests aid code reuse. Both your code and your testers should be migrated to your new project. Adjust the code again until the tests run.

Unit Tests

What Do Unit Tests Look Like?

An individual unit can be a single line of code, a method, or a class, among other things. In general, more minor is preferable. Smaller tests provide a more detailed picture of how your code is performing. There’s also the tutorial aspect of testing minimal units: your tests may be done very quickly, like a thousand tests in a second.

Consider the following sample code: 

def divide (a, b)

  return a/b


Using Ruby, small tests might look something like this: 

class smallTest < MiniTest::Unit::testCase

  def tiny_test



    assert_equal(3, divider(a, b))




This example is overly simplistic. However, it illustrates what we mean when we say little. Small tests can make it more difficult to cross-systems, such as from code to a database or a third-party system. Crossing systems isn’t wrong, but it can have implications, such as gradually slowing down your tests. 

Who Should Create The Unit Test Then?

Unit testing is frequently included in the programming phase. This isn’t because programmers are the masters of unit testing; it’s just rational thinking. The programmer who built the test code will most likely know how to get to the bits that can be easily tested and fake objects that can’t be reached otherwise. It’s a trade-off in terms of time. Occasionally, someone will step in and write tests to assist in building safeguards while they rework or further develop that section of the codebase.

How to do Unit Testing

Unit Testing

UnitTest is a framework developers use to create automated test cases for unit testing. Developers write a part of code to test a specific function in a software application as a portion of Unit Testing. Developers can isolate this function to test it more thoroughly, revealing any superfluous dependencies between the tested functions and other units, which can then be removed. 

Unit Testing is of two types

  1. Manual testing
  2. Automated testing

Unit testing is usually automated, although it can also be done manually (testing manual). However, there is no preference in software engineering for one over the other, test automation is favored. A step-by-step paper may be used in a manual method to perform unit testing.

Automated unit testing

Under the Automated Approach

A developer creates a block of code in the program only to test the function (functional testing). When the program is posted, they will comment out and in the end remove the test code. A developer could potentially isolate the function to test it thoroughly. This more extensive unit testing method entails copying and pasting code into its testing environment rather than the natural one. Separating the code aids in discovering unneeded dependencies between the code under test and other units or data spaces in the product. These reliances can then be removed. To produce automated test cases, most programmers use the Unit Test Framework. The developer uses an automation framework to code criteria into the test to ensure correct code. The framework logs failing test cases while they are being executed. Many frameworks will also automatically detect and report these failed tests (test fail). The framework may halt subsequent testing depending on the severity of a failure.

 The Unit Testing workflow is as follows:

  1. Create Test Cases 
  2. Conduct a review/rework
  3. Establish a baseline 
  4. Carry out the test cases.

Unit Testing Techniques

Unit Testing Techniques

Unit testing techniques are divided into 3 categories: 

  1.  Back box testing
  2. White box testing
  3. Gray box testing
Black box testing It involves testing the user interface as well as input and output
White box testing  It consists in testing the software application’s functional behavior
Gray box testing It involves executing test suites, test methods, test cases, and risk analysis.

 The following are the code coverage strategies utilized in unit testing

  1. Statement Coverage
  2. Decision Coverage
  3. Branch Coverage
  4. Condition Coverage
  5. Finite State Machine Coverage

Unit Test Example

Mock Objects

Mock objects are utilized in unit testing to test pieces of code that aren’t yet part of a complete application—mock objects stand in for the program’s missing elements. You may have a function that needs objects or variables  that have not yet been created. Those will be accounted during unit testing in the form of mock objects explicitly produced for the unit testing of that code area.

Unit Testing Tools

Tools in Unit Testing

To assist with unit testing, there is a number of automated unit test software available. We’ll give you some samples below:

  • Junit: Junit is a Java programming language testing tool that is free to use. It contains assertions that can be used to identify test methods. This utility initially tests the data(test data) before inserting it into the code.
  • NUnit: NUnit is a popular unit-testing framework that works with all.NET languages. It’s an open-source program that allows you to write scripts manually. It will enable you to execute data-driven tests in parallel.
  • JMockit: It is a free and open-source unit testing software. It’s a code coverage testing tool that includes lines and execution paths measurements. It has recording and verification syntax for copying APIs. Data coverage, Path coverage, Line coverage, and  are all available with this tool.
  • EMMA: EMMA is a free and open-source test set for evaluating and reporting Java code. It is Java-based. Therefore there are no external library dependencies, and the source code is available. Method, line and basic block coverage kinds are all supported by Emma.
  • PHPUnit: PHPUnit is a PHP programmer’s unit testing tool. It takes tiny portions of code, known as units, and tests each separately. The tool also allows developers to assert that a system behaves specifically using pre-defined assertion techniques.

These are just a few of the unit testing tools out there. There are a lot more, notably for C and Java, but regardless of the language you use, you will be able to find a unit-testable tool to meet your needs. 

Test-Driven Development (TDD) & Unit Testing

Test-Driven Development (TDD)

TDD makes sizeable use of testing frameworks when it comes to unit testing. To create automated unit tests, a unit test framework is used. Unit testing frameworks aren’t unique to TDD, although they are critical. We will look at some of the benefits of TDD in the field of unit testing below:

  • Make substantial use of testing frameworks.
  • Before the code is written, the tests are written.
  • It is now possible to integrate easily and quickly.
  • The applications’ classes are all put to the test.

Unit Testing Myth

Myths are, by definition, false assumptions. These assumptions create a vicious cycle: The truth is that unit testing speeds up development. Integration Testing, programmers believe, will catch all mistakes and not run the unit test. Simple errors that could have been detected and repaired quickly in unit tests require a long time to trace and fix once the units are combined.

Advantages of Unit Testing

Unit Testing Advantages

The following are a few of the benefits of unit testing:

  • Unit tests provide developers with a fundamental overview of the unit API to discover what functionality a unit offers and how to use it.
  • Unit testing allows the programmer to rewrite code later while ensuring that the module functions correctly (i.e., Regression testing). The practice is to create test use cases for all functionalities and methods so that any modifications that cause a problem can be swiftly discovered and corrected.
  • One can test portions of the project without waiting for others to finish due to the modular structure of unit testing.

 Disadvantages of Unit Testing

Unit Testing Disadvantages

  • It is unrealistic to expect unit testing to catch every bug in a program. It is impossible to assess all possible execution routes, even in the most straightforward programs.
  • By definition, unit testing focuses on a unit of code. Consequently, it is unable to detect integration or system-wide issues. 

Unit testing should be used in conjunction with other types of testing techniques.

Unit Testing Best Practices

Best Practices of Unit Testing

  • Cases for unit tests (unit test cases) should be independent. Unit test cases should not be affected by any upgrades or changes in requirements.
  • Only one code should be tested at a time.
  • For your unit tests, use explicit and consistent naming standards.
  • Before modifying the implementation of any module, make sure there is a corresponding unit test case for the module and that the module passes the tests (test pass).
  • Before moving on to the next phase of the SDLC(software development cycle), any bugs discovered during unit testing must be resolved-debugging.
  • Adopt a “test as code” testing strategy. The more code you write without testing, the more pathways you’ll have to go through to look for issues. 

Relevant Information on Unit Testing

Unit Testing Relevant Information

End-to-end tests (end testing) are another problematic area. Getting your system in a specific ‘test ready’ condition usually involves careful ordering, dependencies on other tests, and careful setup. There are a lot  technologies available for this purpose, just as there are for integration testing.

Quality assurance in Software Testing

Software testing quality assurance is a technique for ensuring the quality of software goods or services is given to clients by a company. Quality assurance is associated with making the software development process more effective and efficient following the software quality standards established for software products. QA Testing is a common term for Quality Assurance.

Quality assurance functions

  1. Technology transfer
  2. Validation 
  3. Documentation
  4. Assuring quality of products
  5. Quality improvement test plans

Code Documentation

Code documentation is a pain, as evidenced by so little written. By encouraging better coding techniques and leaving behind portions of code that describe what your product is doing, unit testing can help ease the documentation burden. You’ll be upgrading a system of checks that are already functioning for you rather than constantly feeding the documentation beast with code changes.

Agile Testing

Agile development and testing are becoming increasingly popular, and as a result, innovative QA/testing teams are keeping up with current development trends. Project management tools to automated testing tools and techniques are examples of agile testing tools.

Test-Driven Development

TDD (Test Driven Development) is a programming technique. A programmer does a writing test before writing any production code and then produces the application code to pass that test. The notion is that with just a smidgeon of confidence from that initial test, the programmer can feel free to rework and refactor some more until they have the cleanest code they can write. 


  • UNIT TESTING is a software testing process (software test) in which individual software units or components are tested (component testing).
  • As you can see, unit testing may be somewhat time-consuming. Depending on the application strategy being tested and the testing methodologies, tools, and philosophies employed, it might be complex or straightforward. Unit testing is always required on some testing levels (testing phases). 
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