What is Thread Testing in Software Testing?

Thread testing is client-server-based testing to verify the primary function of an application. It is used to determine whether the application can run a specific task or thread or not.

Why Thread Testing is important?

Software is split into several threads with each thread running a specific task. When all components of the software are integrated, it is time for the developer to ensure the program runs as expected. For example, if it is a banking app, then the developer must make sure the app can execute all the transactions as per the client’s requirement. This is where thread testing comes to the action.

The testing involves integrating all threads through preset levels. It generally starts from the subsystem until it covers the whole system.

What are Threads in software development?

Threads are a single sequential flow of control in a process. In other words, it is the smallest executable task of the system.


Let’s take a web browser as an example. A web browser consists of several threads running simultaneously. There is one thread for displaying images and texts while another for retrieving data. In some cases, you may need a single application to execute all the processes.

Generally, when you send multiple requests, the server acknowledges each request one by one. As a result, it takes up a whole lot of time, eventually making the system slow. This can be solved by creating multiple threads as they can respond to several requests at the same time.

How to Perform Thread Testing?

Thread testing is conducted at the initial phase of the system integration testing process. For this, you need to accurately plan how to put modules in the correct order to integrate them into a complete system.

You can integrate the modules by the following techniques −

  • Big-bang approach − All modules are integrated into a single step. Mostly used for small systems only.

  • Top-down approach − It involves testing the top-level modules first followed by integrating and testing their subroutines.

  • Bottom-up approach − It starts with testing the subsystems individually before testing the complete system.

  • Mixed integration testing − It is a combination of both top-down and bottomup approaches.

Salient features of thread testing:

  • Thread testing is conducted with an incremental process. Meaning you need to integrate threads at a sub-system level and test them before moving towards a complete system.

  • It is conducted at the earliest stage of integration testing, which gives a clear idea to testers for what to test next.

  • Both negative and positive scenarios are applied and executed within the thread boundaries. Also, both exceptional and boundary cases need to be followed.

  • The developer provides the thread definition to the tester. It helps in testing the thread as set by the integration testers. A thread review process is conducted to pass further information to the testers.

  • The thread testing is only limited to integrate different modules. It is not a part of an end-to-end development process.

  • When it comes to testing multiple functionalities, it is important to activate all instances to be tested at the same time.

  • The multi-thread program needs to be executed on different hardware.

  • Thread testing is also considered session testing as you need to form sessions of thread. However, remember that a formed thread is not always a session.

Types of Thread Based Testing

Thread testing is divided into two types: Single thread testing and multi-thread testing.

  • Single Thread Testing − It is performed by testing one transaction at one time. when a client sends a request as it responds one client at a time, resulting in a longer response time. This testing is useful in evaluating and testing the logic of written code.

  • Multi-Thread Testing − It is executed by testing multiple active transactions simultaneously. It is conducted by preparing separate threads for a service or testing the responsiveness of a request.

Single or multithread approach? Which is better?

Applications with the multithread approach are better as it enables several resources to work on a request at the same time. Which in return saves time and improves the application’s performance.

Thread Testing Challenges

Several challenges are documented while performing thread testing −

It is often complex to write unit test cases, especially for multi-threaded codes.

Setting the right environment can be challenging for multi-thread testing as you need to conduct it on various hardware, memory, storage, etc.

You need to prepare separate test case scenarios for single threads and multiple threads.

Benefits of Multi-thread approach

Multi-threaded is highly preferable by testers as −

  • It enhances the responsiveness as you can run the application even if part of it is blocked.

  • It allows you to share the resources of the process they belong to.

  • Creating threads is cost-effective as you can share the resources they belong to.

Disadvantages of Multi-thread approach

Despite its immaculate benefits, the multi-thread approach does come with some disadvantages as well.

  • The testing process can be complicated

  • Writing a program is difficult

  • Deadlock can occur frequently

  • Results are often unpredictable

What Is Deadlock?

Every object in a program comes with a unique lock. If a thread wants to execute a synchronized method to an object, you need to let it lock with that object. Once the method execution process completes, the thread automatically releases the lock. An object-level lock is a mechanism to synchronize non-static methods or code blocks in a way that only one thread can execute a code block for a single instance of the class. It is done to safeguard an instance-level data thread.

Sometimes situation happens when one thread is waiting for an object lock which is acquired by another thread. Similarly, the second thread is also waiting for an object lock acquired by the first thread. Since both are waiting for each other, this can create a deadlock.


Thread testing is an integral part of the testing cycle as it serves a wider scope i.e, testing major functionalities as well as a specific task or thread. This makes this methodology perfect for client server-based architecture. Although testers face several challenges, this test is also essential to determine the robustness, reliability, and functionality of the application.

Updated on: 20-Aug-2021

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