Unit testing is a software testing technique in which individual units or components of a software application are tested in isolation from the rest of the system. The purpose of unit testing is to validate that each unit or component of the software works as intended and meets the specified requirements. It is a crucial part of the software development process, as it helps to catch bugs early on in the development cycle, reducing the overall cost and effort required for fixing them.

One of the key benefits of unit testing is that it enables developers to make changes to the code with confidence, knowing that the changes will not have unintended consequences. This is because unit tests provide a safety net that can catch any issues that may arise from changes made to the code. This results in more robust software, which is less prone to bugs and more reliable for users.

1. What is Unit Test?

Unit Testing (UT) is a type of software testing in which individual units or components of the software are tested. Unit testing is performed during application development. The goal of unit Testing is to isolate a piece of code and verify the correctness of that unit.

Unit testing is typically done using a unit testing framework, which provides tools and libraries for creating, executing, and managing tests. There are many popular unit testing frameworks available, including JUnit, NUnit, and xUnit, each with their own unique features and capabilities. The choice of framework will depend on the specific requirements and constraints of the software being developed.

1.1 What are units?

A Unit is the smallest testable PM component such as functions, procedures, classes, or methods.

Since the Unit selected for testing is usually small in size and simple in operation, it is not difficult for us to organize, test, record and analyze test results, so error detection will be easy. It is also relatively easy to determine the cause and fix it because it is only zoning in a Unit under test.

Each UT will send a message and check whether the received answer is correct or not, including:

  • Desired return results
  • Expected Exception Errors
  • UT codes work continuously or periodically to probe and detect technical defects during development, hence UT is also known as automated testing technique. UT has the following characteristics:
  • Acting as the first users of the system.
  • Only being valuable when they can detect potential problems or technical errors.

1.2 Definitions of Terms

Assertion: A statement that describes the checks to be performed, for example: AreEqual(), IsTrue(), IsNotNull()… Each UT consists of multiple assertions that check the output data, the correctness of the statements. Exception errors and other complex issues such as: – Existence of an object – Boundary condition: Whether the values ​​are out of bounds – Order of execution of data streams…

Test Point: this is the smallest unit of test, containing only an assertion to confirm the correctness of a certain piece of code. Every project member can write a test point. Test Case: A set of test points to test a specific functional feature, for example the entire period of user input until the information is entered into the database. In many special and urgent test cases may not need test cases.

Test Suite: A collection of test cases defined for each module or subsystem.

Regression Testing (or Automated Testing): This is a method of automated testing using a special software. The same type of test data is automatically repeated over and over again to prevent old errors from reoccurring. Combining Regression Testing with Unit Testing will ensure that new pieces of code still meet the changing requirements and old pieces of code will not be affected by maintenance activities.

Production Code: The main part of the application code that is delivered to the client.

Unit Testing Code: Sub-code to test the main application code, not delivered to the client.

2. Unit Testing Lifecycle

UT has 3 basic states:

Fail (error status)

Ignore (temporarily suspended)

Pass (working status)

The entire UT is operated in a separate system. There are many PMs that support UT execution with an intuitive interface. Usually, the status of the UT is represented by different colors: blue (pass), yellow (ignore) and red (fail).

UT is only really effective when:

  • Operated repeatedly
  • Fully automatic
  • Independent of other UTs.

3. Unit test design

Each UT is designed in the following sequence:

  • Setting the necessary conditions: initializing objects, determining the required resources, and constructing dummy data…
  • Invoking the methods to be tested.
  • Checking the correct operation of the methods.
  • Cleaning up resources after finishing the test.

4. Unit test application

  • To check every smallest unit that is properties, events, procedures, and functions.
  • To check object states and constraints at deeper levels that are not normally accessible to us.
  • To check processes and, by extension, frameworks (workflow – collection of processes)

5. Benefits of applying Unit test

In the beginning, people are often hesitant to write UT instead of focusing on code for business functions. Writing Unit Tests can take a lot more time than coding, but has the following benefits:

Creating the ideal environment to test any piece of code, has accurate probing and error detection, maintains the stability of the entire PM and saves time compared to traditional debugging.

Detecting inefficient execution algorithms, procedures that run beyond the time limit.

Detecting problems related to designing, system handling, even designing models.

Detecting potentially fatal errors in very narrow situations.

Creating a safety fence for code blocks: any change can affect this fence and report potential dangers.

In the working environment Unit Test also has a great effect on work productivity:

Freeing QA professionals from complex testing tasks.

Increasing confidence when completing a task. We often have a feeling of uncertainty about our code such as whether the errors will return, the operation of the current module will be affected, or whether the code modification work has broken somewhere…

As a tool to evaluate your ability. The number of test cases that change the “pass” state will show your working speed and productivity.

6. How to code effectively with Unit Test

Analyzing possible scenarios for the code. Don’t ignore the worst possible scenarios, for example data entry causes a database connection to fail, application crashes because of a division by zero operation, procedures throw an exception Mistakes can mysteriously crash apps…

Every UT must start with a “fail” state and transition to a “pass” state after a reasonable number of changes to the main code.

Every time you write an important piece of code, write the corresponding UTs until you can’t think of any more scenarios.

Entering a sufficiently large number of input values ​​to detect code weaknesses in principle:

If a valid input value is entered, the returned result must also be valid

If an invalid input value is entered, the returned result must be invalid

Early detection of unstable and potentially error-prone code, write the corresponding UT to control.

For each business object or data access object, it is recommended to create a separate test layer because serious errors can arise from these objects.

To prevent possible errors from automatically executing all UTs every time a significant change is made, doing this every day. Error UTs tell us which change caused the error.

To increase efficiency and reduce risk when writing UTs, it is necessary to use a variety of testing methods. Writing as simply as possible.

Finally, writing Unit Test also requires effort, experience and creativity like writing software.

Making sure that each unit test case will be independent of the other test cases. It is not recommended to call another test case within a test case. Test cases should not depend on each other in terms of data and execution order.

Always test each module independently. Otherwise, there will be a lot of overlap between test cases and changes to one unit can affect all other modules and cause the software to fail.

Name test units clearly and consistently. Making sure that the test cases are easy to read, anyone can select the test case and run it without any problem.

When implementing changes to the interface or functionality, it is necessary to rerun the previous test cases to ensure that this change does not affect the passed old test cases.

Always make sure bugs identified during Unit testing are fixed before moving on to the next stage.

Not to try to write test cases to test everything, instead focus on testing the influence of system behavior.

Besides writing test cases to test the system behavior, it is necessary to write more test cases to test the performance of the source code

Test suites should be separate, independent of the code from the module

It is not recommended to have multiple asserts in a test case because when one condition is not satisfied, other asserts will be ignored.

After a long time, the number of test cases is high, the running time is large. It is recommended to divide into groups of old test cases and new test cases, old test cases will run with less frequency

Before ending this section, Novatesting has a piece of advice that writing UT is similar to coding a program, what you need to do is keep practicing. Remember that UT is only really beneficial if we put software quality first rather than just to finish the job on time. Once you’ve mastered the work of writing UTs, you can read more about more complex UT construction techniques, among them virtual object modeling, which will be covered in the next section.

7. Misconceptions about Unit testing

Integration testing will find all bugs anyway: This is one of the common misconceptions. The difficulty of the problems will increase in the software testing process. The later stages of testing, the more complex, design bugs are.

Many programmers think that Unit testing is not required. Many people believe that their programming skills are already good and that their software does not need to have unit tests. But in this real world, everyone can make mistakes and the actual software systems are much more complicated.

Writing Unit tests takes too long: Programmers often think that unit testing is meaningless to them because they think that the source code will always be tested by testers. However, if unit testing is not performed, the number of bugs found at later stages will increase, and the more at the later stage, the more complicated the error will be, taking a lot of time and cost to fix.

So, what is called a good unit test?

  • Fast
  • Independent between test cases, regardless of test order
  • Using data that is easy to read and understand
  • Using real data when possible
  • simple, easy to read, easy to maintain test cases
  • true reflection of the module’s operation

In conclusion, unit testing is an essential part of software development, and it plays a critical role in ensuring software quality and reliability. It helps developers to catch bugs early on in the development cycle, reducing the overall cost and effort required for fixing them, and enables developers to make changes to the code with confidence. By incorporating unit testing into their development processes, organizations can ensure that their software applications are robust, reliable, and of high quality.

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