Learn how to harness AI for faster, more stable tests | Join us

SIT vs. UAT: A Guide For QA Engineers

The software testing landscape is constantly changing, and organizations require QA engineers more than ever. Systems integration testing (SIT) and…

By Erin,

The software testing landscape is constantly changing, and organizations require QA engineers more than ever. Systems integration testing (SIT) and user acceptance testing (UAT) are very important for testing firms as well as for organizations. However, a lot of people confuse the two. This post will help you understand both of these concepts, their differences, and their significance.

Understanding the Basics of SIT vs. UAT

SIT and UAT are two different types of software testing. The development and successful release of any program involve these two tests in separate phases performed by the developing team or by the end user. Both are quite different and require a different set of working rules.

Expand Your Test Coverage

Fast and flexible authoring of AI-powered end-to-end tests — built for scale.
Start Testing Free

Role of the QA Team

Every organization, whether it’s a startup or an enterprise, aims to deliver the best products to its customers. For that, they need a review from the QA engineers. The team reviews the products thoroughly and tests them afterward to get valuable feedback from product owners and customers.

QA and UAT are often confused with each other since they both involve testing. However, they have different objectives. The difference is that QA aims for error-free software whereas UAT ensures that users get the product they want.

QA teams slick the process in such a way that the UAT is more customer friendly. A QA team’s focus on quality can in turn improve the UAT testing and thus deliver a high-quality product.  

Developers VS QA Engineers, I Develop Applications vs I Test Applications | sit vs uat
Image: Role of Developers vs. QA Engineers

Understanding System Integration Testing

Let’s break this into parts: system, integration, and testing to understand SIT. A test that checks the integration between different systems is known as system integration testing. A system is not the end product. Various integrations form the end product. For example, e-commerce systems are compiled with payment gateways that receive the order and payments from the customer. There are plenty more examples where various systems comprise the desired end product.

There are different kinds of integrations:  

  • Hardware-hardware
  • Software-software
  • Hardware-software.

An e-commerce website using a payment gateway is an example of software-software integration. A car that uses internal sensors is an example of hardware-software integration. Putting different types of physical equipment together is an example of hardware-hardware integration.

Understanding User Acceptance Testing

To understand user acceptance testing, start by thinking of an everyday example where you go to a shop and purchase something you want. After receiving what you asked for from the store employee, you make sure that the order prepared meets your requirements. Similarly, when a user asks developers to create a product, they review it to make sure it matches what they asked for. This process is known as user acceptance testing, sometimes shortened to acceptance testing.

UAT is the last step before the release. There are three basic types: functional acceptance, operational acceptance, and regulatory acceptance.

Does SIT Come Before UAT?

User acceptance testing is the final phase of software testing where the users test the software and decide whether it’s fit for use. If the users are satisfied with the performance of the software, it passes user acceptance testing.

UAT is commonly performed in a production environment. There may or may not be a significant difference in how the software performs in a testing environment and UAT. Therefore, UAT is either performed before or after SIT, depending upon need and applicability.

Learning the Differences Between SIT vs. UAT

How SIT Works

You have already seen what SIT is. Now let’s look at how it works. There are four different steps:

  1. Integrating the individual units
  2. Testing the integrating system
  3. Writing and performing tests according to the system requirements
  4. Making sure there are no errors

There are two main techniques, a top-down approach, and a bottom-up approach. Also, there is another approach, known as the Big Bang approach.

1. Top-Down Approach

You should have a decent idea about the top-down approach from the name itself. The integration and testing are performed in a top-to-bottom manner. This approach begins with modules integration first, followed by the subsystems and systems. Where the submodules or subsystems are absent, dummy modules known as stubs are used. They have minimal functionality, but you can still use them until the actual module is ready.

Subsystem integrations are generally tricky and thus carry some drawbacks along with them.

top down approach - sit vs uat
Image: Top-Down Approach

2. Bottom-Up Approach

The bottom-up approach is the opposite of the top-down approach. You should first integrate and test the lower modules, followed by the main modules. We refer to the set of lower modules as clusters. Where the main module is not present, drivers are used. Unlike the top-down approach, it is less error-prone.

The Big Bang approach in system integration testing is a methodology that involves testing all system components together

3. Big Bang Approach

The Big Bang approach in system integration testing is a methodology that involves testing all system components together. This approach is typically used when there is a tight deadline for testing, and all components need to be tested simultaneously. The Big Bang approach can effectively find defects that occur in case of integrated components.

How UAT Works

Here are the working steps for UAT:

  1. Make a plan based on the requirements
  2. Prepare test cases and test data according to the requirements
  3. Test for bugs
  4. Send the project to production
  5. Stall production if you find any more bugs at this stage

Types of UAT

There are two types of UAT: alpha testing and beta testing. In alpha testing, customers or users test the product at the development site. In beta testing, customers or users test the product at their sites. Developers have no role here.

Alpha testing is a more controlled environment where the testers better understand the system under test. On the other hand, Beta testing is more of a real-world test, where users are testing the system in their own environment.

Summarizing the Differences

Here’s a summary of these differences:

Prefers interfacing between the modules Focuses entirely on the user’s requirements
Follows individual unit testing but before system testing Follows system testing
Developers perform the testing Customers and end-users perform the testing
Issues encountered here can be problems with data flow, control flow, etc. Issues encountered here tend to be functionality problems, e.g., the program doesn’t work according to the user’s prerequisites.


We hope you now understand what SIT and UAT are, how to use them, and why they are necessary parts of the software development lifecycle. If you would like to learn more about how you can use software testing to help you achieve your software development goals, or if you want to learn more about best practices for testing software and the right tools, Testim is the right thing for you. Testim is an AI-based testing platform for fast authoring and stable tests used by customers such as Microsoft, NetApp, and Sprinklr. At Testim, our only goal is to make QA testing open, flexible, and customizable so that QA engineers can code or record their tests easily.

What to read next

5 Key Considerations for Evaluating UI and End-to-End Automated Testing Solutions

What Is the Software Testing Life Cycle? A Complete Guide

Testim's latest articles, right in your inbox.

From our latest feature releases, to the way it impacts the businesses of our clients, follow the evolution of our product

[formidable id=2]