An Introductory Guide To Unit Testing | Techniques, Tools & Best Practices

“Hey! The new features of the app are crashing frequently!” These words are like a disaster for your product's reputation. So, as you want your business to reach the heights of success, you will never wish to experience such a pathetic nightmare of your app's features breaking down for carelessness in testing them thoroughly.

Yes, testing is that massive part of your product's journey that ensures its best performance in every possible situation.

Importance of Software Testing

You may think that your users are always looking for new features, so you should focus on developing amazing features only.

But, you must know that even if your app has numerous useful features and functionalities, it may not perform at its best. If you do not prioritize testing your app in every possible scenario, it may experience the following problems -

  • As you keep on adding new complex features to your app, the codes working behind them also continue to become more complex. As a result, the codes become likely to have more bugs.
  • You may have awesome features but, you haven't tested them to perform simultaneously. Due to that, if any user tries to use multiple features at the same time, they become prone to breaking down.
  • No matter how many useful features and functionalities your app has, if the server isn't capable of handling huge user traffic, the entire application will keep crashing.
  • Whenever you try to add a new feature, the existing code may get affected negatively. This is also a major objective of testing.
  • Having countless functionalities is not the last thing to worry about. They must perform at their best efficiency to satisfy your users and create a positive reputation for your app.

All these problems and many more like them can be avoided only by executing strategic tests on your app. The “strategy” part is extremely crucial here. Only if you follow a proper strategy for your test suite, then you can expect proper results from them.

The universally followed most effective testing strategy is called by a defining name i.e. Testing Pyramid. You can know all the details about it in the article “Testing Pyramid - A Path To Achieve Efficient QA”.

What Is Unit Testing?

As we went through the importance of Software Testing, it's time to know about its largest subset. Unit testing is the traditional name for testing every small isolated part of a tech product. That means these tests are only concerned with the components that have no dependencies on the external parameters.

It can be termed as a part of a whiteboard testing technique. Here, the tester knows about the internal implementation of the software being tested. You can get to know everything about how to perform Unit Testing from the article “What Is Unit Testing? Definition, Basics, and Types

When Should You Conduct Unit Tests?

Executing unit tests means you are testing the smallest code blocks that are called units and most importantly the tests are absolutely isolated from the external aspects.

So, naturally, there are some ideal scenarios where you must execute unit tests. The following parts of your app must be tested through unit tests.

  • The complex parts of the codebase as they are highly tentative to break down.
  • The parts of your code that have a lot of bugs.
  • The codes that express important logic for your business.

The parts of your app that have huge dependencies on external parameters must be avoided for unit tests.

How To Do Unit Testing?

As you previously saw, unit testing means testing in isolation. Hence, in those tests, exclusive lines of code are written to test a specific portion of a software application.

Testing those portions in isolation leads to the revelation of dependencies between the function/component being tested and other units.

Though traditionally Unit Test Frameworks are used for creating automated unit tests, the amazing no-code testing tools like Preflight can enable anyone to execute awesome tests irrespective of having coding knowledge.

You may have already seen in the article “What Is Unit Testing?” that Unit Testing is of two types i.e.

Though traditionally unit tests have been executed manually, to cope with the surge in speed, the number of users, and the demand for efficient features, automated testing is being given great preference. Hence, we are jotting down a brief explanation of the automated approach here.

  • In the automated unit testing approach, a section of code is added to the application. After completing its objective of testing function and when the application is deployed, that test code is commented out and finally removed.
  • As you previously saw, a thorough and efficient unit testing practice demands the function to be isolated. In this practice, developers often need to copy and paste code to its own testing environment rather than its natural environment. This isolation method helps in identifying the unnecessary dependencies between the code being tested and other units or data spaces in the product. It eventually helps in eliminating those dependencies.
  • Automated test cases are usually developed by using a Unit Test Framework. The advantage of using such frameworks is that they enable developers to create criteria that verify the correctness of the code. One of the prime duties of these frameworks is keeping the log of failing test cases. Some of them are even capable of flagging & reporting failed test cases, and can even halt subsequent testing.
  • The most commonly followed workflow of Unit Testing is -
  1. Creating test cases.
  2. Reviewing/reworking.
  3. Determining the baseline.
  4. Executing the test cases.

Unit Testing Techniques

Based on operational techniques, unit testing techniques are mainly divided into three categories i.e.

  • Black Box Testing: In this testing method, the user interface is tested along with input and output.
  • White Box Testing: It involves testing the functional behavior of the software.
  • Gray Box Testing: Its common uses are executing test cases, test suites, test methods, and performing risk analysis.

Commonly used code coverage techniques used in unit testing are as follows -

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

As the title of this section suggests, there are numerous automated unit testing tools available in the market. And, though each one of them gives a terrific competition to the others, we are here jotting down five highly renowned among them.

  • Junit: Who doesn't love a tool that is free to use? Well, the good news for Java users is that Junit is a free-to-use testing tool for your favorite programming language. With this tool, you get to use assertions for identifying test methods. The operation of this tool consists of testing the data first. Then it is used for testing the specific piece of code.
  • NUnit: The best part about this tool is that it is open source. It has immense popularity for being used in apps developed in .net languages. With this tool, you can run data-driven tests in parallel.
  • JMockit: It is another amazing open-source testing tool. It is also termed as a code coverage tool with line and path metrics. The awesome advantage of using this tool is that it offers Line Coverage, Path Coverage, and Data Coverage. Also, this tool is famous for allowing mocking API with recording and verification syntax.
  • EMMA: This amazing open-source toolkit is primarily used for analyzing and reporting code written in Java language. The coverage types supported by EMMA are method, line, basic block, etc. Being Java-based, it is capable of operating without external library dependencies and can easily access the source code.
  • PHPUnit: Here comes the testing pro for PHP programmers. If you are willing to test PHP codes, PHPUnit is the best choice for you. It is also an amazing unit testing tool with the capability of testing units (small pieces of code) separately. And, the best part is that using this tool, you can pre-define assertion methods to assert that a system behaves in a certain manner.

However, today's era is looking for much better efficiency through amazing no-code testing tools like Preflight. And, for that, you can just simply book a demo.

Test-Driven Development (TDD) & Unit Testing

There is no need to specifically mention the popularity of Test Driven Development. But, the good news is that using efficient testing frameworks makes it tremendously easy and advantageous to execute Unit tests in TDD.

The primary function of a unit test framework is to create automated unit tests. Those frameworks are essential to TDD. The result of associating TDD with unit testing is explained below -

  • Tests are written before the code.
  • They have a massive reliance on testing frameworks.
  • You get the scope to test all classes in the application.
  • It allows you to achieve quick and easy integration.

Unit Testing Myth and The Reality

There are some interesting and funny myths about unit testing. The two most popular ones among them are -

  • Unit testing requires time and it can hamper your tight schedule.
  • Your code is very strong and robust, so you don't need unit tests.

As the title says, the above ones are the myths you are having about unit testing. The reality is that unit tests are a great booster to the speed of development.

Another huge mistake that is often done by testers is thinking that integration tests can identify all errors and as a result of this misconception, they skip conducting unit tests.

But, in reality, it leads to a situation where there are so many small errors that could be easily identified and corrected through unit tests but they have now become extremely time-consuming to be traced and fixed.

Benefits of Running Unit Tests

Well, it's pretty obvious that there are strong reasons behind such immense popularity of unit tests.

There are numerous awesome benefits of unit testing that lead towards the great performance of your application. So, let's check out more details about them.

Code Refactoring

If you are planning to run good unit tests, you will never have to worry during refactoring or re-writing your code. Executing efficient unit tests provides you with the assurance that refactoring your code will never cause the breaking of any other functionality.

Easy Addition of New Features

Unit testing lets you stay relaxed during adding new features to your app's codebase. All you have to do is re-running all your small unit tests whenever you add a new feature. This will ensure that the existing features are working perfectly.

Reusing Code

Unit tests make you habituated to writing modular code that is a more dynamic approach. As your features are separated into independent modules, the modular codes make it much easier for you.

Whenever you want to copy a feature to another codebase, you just need to copy the module and tests to the new codebase. Then you are free to re-run the tests to check if anything is broken.


Well-written unit tests mean you get detailed documentation for your codebase along with great accuracy. The unit tests' documentation provides you with information like the working of your code, their input, output, etc.

To ensure that this documentation always remains up-to-date, whenever your code is updated, unit tests are also updated.

Early Identification of Bugs

As unit tests check every smallest bit of your code, you are left with no other option than to think through every piece of code before writing it. This makes it easier to identify every bug before deploying the software. Hence, eventually, unit tests save you a lot of time and money.

Limitations of Unit Testing

Like every great innovation of technology, unit testing also has some limitations. Get to know them in detail below -

  • Though unit testing is the largest subset of software testing, it is the lowest form of testing with a very specific and narrow use case. Hence, it becomes unable to identify all the bugs in your software and it becomes necessary to run higher-level tests like integration tests and system tests to ensure the best quality of your software.
  • Unit testing is very time-consuming and sometimes complex too. Becoming an expert in it is not easy at all. To test every line of code, you may need to write multiple lines of test code. As a result, your codebase becomes so large that it becomes tremendously harder to maintain.

Best Practices

Here, we are jotting down some best practices for unit tests so that you can achieve the best results.

  • Having assert statements in unit tests can make it possible to render the results easily.
  • The most effective anatomy of unit tests is described by “AAA” (Arrange, Act, Assert). It defines the procedure of starting off the test by setting up the class instance in the state you want it (usually be instantiating it and then whatever else you want), executing your test, and then verifying the consequences.
  • In most cases, there should be one assertion per test method, not multiple.
  • Unit tests that do not assert are considered passing but as they are not testing anything, they are also considered fake.
  • Unit tests should be kept simple and localized. If you write multi-threading, file I/O, database connections, web services, etc. for unit tests, they rather become integration tests.
  • You must keep in mind that unit tests are fast. So, ensure that your entire automated unit test suite executes in seconds or quicker.
  • As unit tests are run in isolation, their order of running should not matter.
  • Ensure that your unit tests do not set or depend on global application states such as public, static, stateful methods, singletons, etc.


Till now, you got to know almost everything you should know about unit testing. But, you must remember that to match the pace with the modern efficient codeless world, you must plan all your tests with Preflight, the ultimate no-code testing tool for everyone.

All you have to do is to sign up and select the most suitable package for your needs. So, what are you waiting for? Book your demo now.

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