Unit Testing Tutorial – What is, Types & Test Example (2024)

ByThomas HamiltonUpdated

What is Unit Testing?

Unit Testing is a type of software testing where individual units or components of a software are tested. The purpose is to validate that each unit of the software code performs as expected. Unit Testing is done during the development (coding phase) of an application by the developers. Unit Tests isolate a section of code and verify its correctness. A unit may be an individual function, method, procedure, module, or object.

In SDLC, STLC, V Model, Unit testing is first level of testing done before integration testing. Unit testing is a WhiteBox testing technique that is usually performed by the developer. Though, in a practical world due to time crunch or reluctance of developers to tests, QA engineers also do unit testing.

Unit Testing Video Explanation

Why perform Unit Testing?

Unit Testing is important because software developers sometimes try saving time doing minimal unit testing and this is myth because inappropriate unit testing leads to high cost Defect fixing during System Testing, Integration Testing and even Beta Testing after application is built. If proper unit testing is done in early development, then it saves time and money in the end.

Here, are the key reasons to perform unit testing in software engineering:

Unit Testing Tutorial – What is, Types & Test Example (1)
  1. Unit tests help to fix bugs early in the development cycle and save costs.
  2. It helps the developers to understand the testing code base and enables them to make changes quickly
  3. Good unit tests serve as project documentation
  4. Unit tests help with code re-use. Migrate both your code and your tests to your new project. Tweak the code until the tests run again.

How to execute Unit Testing

In order to execute Unit Tests, developers write a section of code to test a specific function in software application. Developers can also isolate this function to test more rigorously which reveals unnecessary dependencies between function being tested and other units so the dependencies can be eliminated. Developers generally use UnitTest framework to develop automated test cases for unit testing.

Unit Testing is of two types

  • Manual
  • Automated

Unit testing is commonly automated but may still be performed manually. Software Engineering does not favor one over the other but automation is preferred. A manual approach to unit testing may employ a step-by-step instructional document.

Under the automated approach-

  • A developer writes a section of code in the application just to test the function. They would later comment out and finally remove the test code when the application is deployed.
  • A developer could also isolate the function to test it more rigorously. This is a more thorough unit testing practice that involves copy and paste of code to its own testing environment than its natural environment. Isolating the code helps in revealing unnecessary dependencies between the code being tested and other units or data spaces in the product. These dependencies can then be eliminated.
  • A coder generally uses a UnitTest Framework to develop automated test cases. Using an automation framework, the developer codes criteria into the test to verify the correctness of the code. During execution of the test cases, the framework logs failing test cases. Many frameworks will also automatically flag and report, in summary, these failed test cases. Depending on the severity of a failure, the framework may halt subsequent testing.
  • The workflow of Unit Testing is 1) Create Test Cases 2) Review/Rework 3) Baseline 4) Execute Test Cases.

Unit Testing Techniques

The Unit Testing Techniques are mainly categorized into three parts which are Black box testing that involves testing of user interface along with input and output, White box testing that involves testing the functional behaviour of the software application and Gray box testing that is used to execute test suites, test methods, test cases and performing risk analysis.

Code coverage techniques used in Unit Testing are listed below:

  • Statement Coverage
  • Decision Coverage
  • Branch Coverage
  • Condition Coverage
  • Finite State Machine Coverage

For more in refer https://www.guru99.com/code-coverage.html

Unit Test Example: Mock Objects

Unit testing relies on mock objects being created to test sections of code that are not yet part of a complete application. Mock objects fill in for the missing parts of the program.

For example, you might have a function that needs variables or objects that are not created yet. In unit testing, those will be accounted for in the form of mock objects created solely for the purpose of the unit testing done on that section of code.

Unit Testing Tools

There are several automated unit test software available to assist with unit testing. We will provide a few examples below:

  1. Junit: Junit is a free to use testing tool used for Java programming language. It provides assertions to identify test method. This tool test data first and then inserted in the piece of code.
  2. NUnit: NUnit is widely used unit-testing framework use for all .net languages. It is an open source tool which allows writing scripts manually. It supports data-driven tests which can run in parallel.
  3. JMockit: JMockit is open source Unit testing tool. It is a code coverage tool with line and path metrics. It allows mocking API with recording and verification syntax. This tool offers Line coverage, Path Coverage, and Data Coverage.
  4. EMMA: EMMA is an open-source toolkit for analyzing and reporting code written in Java language. Emma support coverage types like method, line, basic block. It is Java-based so it is without external library dependencies and can access the source code.
  5. PHPUnit: PHPUnit is a unit testing tool for PHP programmer. It takes small portions of code which is called units and test each of them separately. The tool also allows developers to use pre-define assertion methods to assert that a system behave in a certain manner.

Those are just a few of the available unit testing tools. There are lots more, especially for C languages and Java, but you are sure to find a unit testing tool for your programming needs regardless of the language you use.

Test Driven Development (TDD) & Unit Testing

Unit testing in TDD involves an extensive use of testing frameworks. A unit test framework is used in order to create automated unit tests. Unit testing frameworks are not unique to TDD, but they are essential to it. Below we look at some of what TDD brings to the world of unit testing:

  • Tests are written before the code
  • Rely heavily on testing frameworks
  • All classes in the applications are tested
  • Quick and easy integration is made possible

Unit Testing Myth

Myth: It requires time, and I am always overscheduled
My code is rock solid! I do not need unit tests.

Myths by their very nature are false assumptions. These assumptions lead to a vicious cycle as follows –

Unit Testing Tutorial – What is, Types & Test Example (2)

Truth is Unit testing increase the speed of development.

Programmers think that Integration Testing will catch all errors and do not execute the unit test. Once units are integrated, very simple errors which could have very easily found and fixed in unit tested take a very long time to be traced and fixed.

Unit Testing Advantage

  • Developers looking to learn what functionality is provided by a unit and how to use it can look at the unit tests to gain a basic understanding of the unit API.
  • Unit testing allows the programmer to refactor code at a later date, and make sure the module still works correctly (i.e. Regression testing). The procedure is to write test cases for all functions and methods so that whenever a change causes a fault, it can be quickly identified and fixed.
  • Due to the modular nature of the unit testing, we can test parts of the project without waiting for others to be completed.

Unit Testing Disadvantages

  • Unit testing can’t be expected to catch every error in a program. It is not possible to evaluate all execution paths even in the most trivial programs
  • Unit testing by its very nature focuses on a unit of code. Hence it can’t catch integration errors or broad system level errors.

It’s recommended unit testing be used in conjunction with other testing activities.

Unit Testing Best Practices

  • Unit Test cases should be independent. In case of any enhancements or change in requirements, unit test cases should not be affected.
  • Test only one code at a time.
  • Follow clear and consistent naming conventions for your unit tests
  • In case of a change in code in any module, ensure there is a corresponding unit Test Case for the module, and the module passes the tests before changing the implementation
  • Bugs identified during unit testing must be fixed before proceeding to the next phase in SDLC
  • Adopt a “test as your code” approach. The more code you write without testing, the more paths you have to check for errors.

Unit Testing Tutorial – What is, Types & Test Example (3)


  • UNIT TESTING is defined as a type of software testing where individual units or components of a software are tested.
  • As you can see, there can be a lot involved in unit testing. It can be complex or rather simple depending on the application being tested and the testing strategies, tools and philosophies used. Unit testing is always necessary on some level. That is a certainty.

You Might Like:

  • What is User Acceptance Testing (UAT)? Examples
  • What is STRESS Testing in Software Testing?
  • Scrum Testing Methodology Tutorial
  • Payment Gateway Test Cases – Tutorial with Testing Scenarios
  • REST Client Testing using Restito Tool: What is Rest Client?
Unit Testing Tutorial – What is, Types & Test Example (2024)


Unit Testing Tutorial – What is, Types & Test Example? ›

There are two main types of unit tests: manual and automation. Both types are used to verify specific components of the system being tested. Unit testing improves program efficiency by ensuring that the individual components all work as intended.

What is unit test types of test? ›

There are two main types of unit tests: manual and automation. Both types are used to verify specific components of the system being tested. Unit testing improves program efficiency by ensuring that the individual components all work as intended.

What are three test cases you should go through in unit testing? ›

These three unit test phases are also known as Arrange, Act and Assert, or simply AAA.

What are the 4 types of test? ›

There are various types of tests in education, from subjective, objective, summative, and formative to diagnostic tests. These tests help gauge students' knowledge and levels of understanding of the course materials.

What are the 6 types of tests? ›

Six types of assessments are:
  • Diagnostic assessments.
  • Formative assessments.
  • Summative assessments.
  • Ipsative assessments.
  • Norm-referenced assessments.
  • Criterion-referenced assessments.
Sep 24, 2021

What is unit testing with simple example? ›

What is Unit Testing? Unit testing is testing the smallest testable unit of an application. It is done during the coding phase by the developers. To perform unit testing, a developer writes a piece of code (unit tests) to verify the code to be tested (unit) is correct.

How do you write a unit test? ›

  1. Test Small Pieces of Code in Isolation. ...
  2. Follow Arrange, Act, Assert. ...
  3. Keep Tests Short. ...
  4. Make Them Simple. ...
  5. Cover Happy Path First. ...
  6. Test Edge Cases. ...
  7. Write Tests Before Fixing Bugs. ...
  8. Make Them Performant.

What are unit testing tools? ›

Unit testing tools are software programs that aid developers in testing individual components or units of their code, ensuring that each one functions correctly. These tools automate the process of creating and running test cases, giving developers prompt feedback on the accuracy of their code.

What are the types of test and examples? ›

Types of exams and tests
  • Diagnostic test. With this test you can test how much your students already know about a given subject or topic. ...
  • Placement test. ...
  • Progress or Achievement tests. ...
  • Internal test. ...
  • Objective tests. ...
  • Subjective tests. ...
  • Useful resources. ...
  • Frequently asked questions.
Jul 22, 2020

What are the 5 tests? ›

Test 1: Invest in community services
  • Test 1: Invest in community services. ...
  • "I'm so isolated and lonely. ...
  • Test 2: Protecting those most at risk. ...
  • Test 3: Reform The Mental Health Act. ...
  • Test 4: Provide a financial safety net. ...
  • Test 5: Supporting children and young people. ...
  • I really need a hug.

What is the most common type of test? ›

Common Test Types. There are three common test types: written tests, oral tests, and physical skills tests.

What is a real time example of unit testing? ›

An example of a real-world scenario that could be covered by a unit test is a checking that your car door can be unlocked, where you test that the door is unlocked using your car key, but it is not unlocked using your house key, garage door remote, or your neighbour's (who happen to have the same car as you) key.

Who write unit test cases? ›

Unit tests are typically created by developers during the coding phase of a project, and are written as code that exists in the codebase alongside the application code it is testing. Many unit testing frameworks exist that help developers manage and execute unit tests.

What are Type 3 tests? ›

Type-III tests, as made popular in commercial statistical software, are not marginal tests and do not follow the principle of marginality when testing lower-order terms: they test the effect of removing a term while leaving all of its higher-order interactions in place.

What are the two major types of tests? ›

Criterion-referenced tests and Norm-referenced tests

This difference in the type of decision to be made forms the basis for two major types of tests – criterion-referenced tests (CRTs) and norm-referenced tests (NRTs).

What are the 2 main types of test in assessment? ›

Formative and Summative Assessments

Most instructors are familiar with the traditional way of assessing students, such as by mid-term and final exams (usually using multiple-choice questions).

What are a list of tests? ›

  • Clinical psychology tests.
  • Cognitive development tests.
  • Intelligence tests.
  • Medical tests.
  • Self tests.
  • Statistical tests.
  • Personality tests.
  • Pure-mathematical tests.

How many types of tests do you know in QA? ›

There are two types of QA testing: manual testing and automated testing.

What is unit testing for beginners? ›

Unit Testing is a type of software testing where individual units or components of a software are tested. The purpose is to validate that each unit of the software code performs as expected. Unit Testing is done during the development (coding phase) of an application by the developers.

Can you explain unit testing? ›

Unit testing is a software development process in which the smallest testable parts of an application, called units, are individually scrutinized for proper operation. Software developers and sometimes QA staff complete unit tests during the development process.

What is unit vs QA testing? ›

Described concisely and directly, Unit Tests is Quality Assurance (QA) for the core of your software. The main difference between Unit Tests and regular QA is that Unit Tests are not done by a user interacting with the software directly. In fact, they are done by a programmer with code.

Is unit test hard? ›

The basics of unit testing are not hard to grasp and master. Unit testing is a process of validating that the smallest building blocks in an application work correctly. Some of these building blocks are independent of the context in which they're used.

How do you write a first unit test? ›

Below are some general guidelines to help you write performance unit tests and testable code.
  1. Keep unit tests short and simple. ...
  2. Consider both positive and negative test cases. ...
  3. Break apart long and complex functions. ...
  4. Avoid network and database connections. ...
  5. Creating a new project. ...
  6. Implementing a class.
Oct 28, 2022

How do you name test cases? ›

Be concise.

Test case names are usually limited to a specific length, so space is at a premium. Make sure to keep names unique while refraining from adding any details that aren't required for identification. You can add those details to the case's instructions or test data, for example.

Why is it called unit testing? ›

A unit test is a way of testing a unit - the smallest piece of code that can be logically isolated in a system. In most programming languages, that is a function, a subroutine, a method or property.

Why is unit test important? ›

The main objective of unit testing is to ensure that each individual part is working well and as it's supposed to work. The entire system will only be able to work well if the individual parts are working well. Unit testing is performed by the software developers themselves.

What is a test type? ›

: any of the printed letters or characters on an eye chart. a typeface carefully chosen for use as test type.

What are short answer type questions? ›

Short answer questions (or SAQs) can be used in examinations or as part of assessment tasks. They are generally questions that require students to construct a response. Short answer questions require a concise and focused response that may be factual, interpretive or a combination of the two.

What are the types of test writing? ›

  • Questions and answers. These can be used to test almost anything. ...
  • True/false. This does not directly test writing or speaking abilities: only listening or reading. ...
  • Multiple-choice. ...
  • Gap-filling and completion. ...
  • Matching. ...
  • Dictation. ...
  • Cloze. ...
  • Transformation.

What is 5 point testing? ›

Five Point Test (5TT) is a neuropsychological test that assesses figural fluency. A participant is asked to generate as many unique designs as possible in a certain time limit. The aim of this study was to create Czech population norms for the Five Point Test.

What are 5 second tests? ›

What is five second testing? Five second testing is a form of usability testing that allows you to measure how well a design quickly communicates a message. This kind of test provides both quantitative and qualitative feedback that helps you optimize a design.

What does the 5 point test measure? ›

The 5PT is a structured and standardized test measuring figural fluency functions. Interrater reliability, test-retest-reliability and construct validity of this measure were analyzed.

Which testing is performed first? ›

In a comprehensive software development environment, bottom-up testing is usually done first, followed by top-down testing.

What are new type tests? ›

Objective type tests are also called as 'new type tests'. These are designed to overcome some of the great limitations of traditional essay type tests.

How many types of testing tools are there? ›

Types of Tools:
S.No.Tool TypeUsed for
1.Test Management ToolTest Managing, scheduling, defect logging, tracking and analysis.
2.Configuration management toolFor Implementation, execution, tracking changes
3.Static Analysis ToolsStatic Testing
4.Test data Preparation ToolsAnalysis and Design, Test data generation
6 more rows

What is unit testing coding? ›

In computer programming, unit testing is a software testing method by which individual units of source code—sets of one or more computer program modules together with associated control data, usage procedures, and operating procedures—are tested to determine whether they are fit for use.

How long does it take to write a unit test? ›

How long does unit testing take? The typical time budgeted on writing unit tests is about 1 day for every feature that takes 3-4 days of heads-down coding. But that can vary with a lot of factors. 99% code coverage is great.

What is end to end testing? ›

End-to-end testing, also known as E2E testing, is a way to make sure that applications behave as expected and that the flow of data is maintained for all kinds of user tasks and processes. This type of testing approach starts from the end user's perspective and simulates a real-world scenario.

How can I improve my unit testing skills? ›

11 unit testing best practices
  1. Write tests for a number of scenarios. ...
  2. Write good test names. ...
  3. Set up automated tests. ...
  4. Write deterministic tests. ...
  5. Arrange, Act, and Assert (AAA) ...
  6. Write tests before or during development. ...
  7. One use case per unit test. ...
  8. Avoid logic in tests.
Mar 30, 2022

How unit testing is done manually? ›

Manual Testing Process
  • Analyze requirements from the software requirement specification document.
  • Create a clear test plan.
  • Write test cases that cover all the requirements defined in the document.
  • Get test cases reviewed by the QA lead.
  • Execute test cases and detect any bugs.
Mar 9, 2023

How much testing is enough? ›

Most software developers catch and fix 99% of their mistakes in a product before deploying it for testing, so it is the role of the tester to find the 1% remaining. This 1% may be neglected by the developers because they assume the end-user wouldn't take that route while using the product.

What are the 5 testing methods? ›

There are many different types of testing, but for this article we will stick to the core five components of testing:
  • 1) Unit Tests. ...
  • 2) Integration/System Tests. ...
  • 3) Functional Tests. ...
  • 4) Regression Tests. ...
  • 5) Acceptance Tests.
Jun 6, 2017

What is a unit test? ›

A unit test is a way of testing a unit - the smallest piece of code that can be logically isolated in a system. In most programming languages, that is a function, a subroutine, a method or property.

What are 2 types of test? ›

Types of Tests
  • Diagnostic Tests. These tests are used o diagnose how much you know and what you know. ...
  • Placement Tests. These tests are used to place students in the appropriate class or level. ...
  • Progress or Achievement Tests. ...
  • Proficiency Tests. ...
  • Internal Tests. ...
  • External Tests. ...
  • Objective Tests. ...
  • Subjective Tests.

What is the difference between unit tests and tests? ›

Functional Testing is carried out to ensure that the application's overall functionality meets the business requirements. Unit Testing is performed on every individual element of an application to ensure that the element works as expected.

What are the 7 stages of testing? ›

Let's look at the different stages of testing in detail.
  • Testing Stage 1 – Test Plan.
  • Testing Stage 2 – Analysis.
  • Testing Stage 3 – Design.
  • Testing Stage 4 – Development.
  • Testing Stage 5 – Execution.
  • Testing Stage 6 – Bug fixing.
  • Testing Stage 7 – Software is implemented.
Nov 18, 2022

Which are 7 key principles of testing? ›

The seven principles of testing
  • Testing shows the presence of defects, not their absence. ...
  • Exhaustive testing is impossible. ...
  • Early testing saves time and money. ...
  • Defects cluster together. ...
  • Beware of the pesticide paradox. ...
  • Testing is context dependent. ...
  • Absence-of-errors is a fallacy.

What are the 4 testing steps? ›

What are the different levels of software testing?
  1. Unit testing.
  2. Integration testing.
  3. System testing.
  4. Acceptance testing.
Nov 8, 2022

Who conducts unit testing? ›

Unit testing is the first layer of the entire testing process software has to go through before its launch and release. This preliminary testing is often carried out by the team of developers or the software engineer that wrote the code for the software.

What is the difference between unit testing and manual testing? ›

Manual unit testing is unit testing that is performed by people. Automated unit testing is unit testing executed without human intervention. You would use manual over automated unit testing when true user input is needed, when automation is too costly, or when unit testing is executed a small number of times.

Is unit testing a box testing? ›

Unit testing is a white box testing technique. White-box testing refers to a methodology that relies on the tester having full knowledge of the internal structure/design of the code being tested. Unit testing requires more effort, but it also gives the software developer a lot of benefits.


Top Articles
Latest Posts
Article information

Author: Terrell Hackett

Last Updated:

Views: 6060

Rating: 4.1 / 5 (72 voted)

Reviews: 87% of readers found this page helpful

Author information

Name: Terrell Hackett

Birthday: 1992-03-17

Address: Suite 453 459 Gibson Squares, East Adriane, AK 71925-5692

Phone: +21811810803470

Job: Chief Representative

Hobby: Board games, Rock climbing, Ghost hunting, Origami, Kabaddi, Mushroom hunting, Gaming

Introduction: My name is Terrell Hackett, I am a gleaming, brainy, courageous, helpful, healthy, cooperative, graceful person who loves writing and wants to share my knowledge and understanding with you.