TDD VS BDD [Detailed Comparison] By TestGrid

tdd vs bdd

Difference Between TDD VS BDD

Over the last decade, software development has shifted from a slow-technical process to an Agile methodology. TDD vs BDD is one of the debates developers talk about a lot.

Agile development entails constant change, and testing has become indispensable in preventing these frequent changes from introducing new bugs or breaking the application in production.

While most developers are familiar with test-driven development (TDD), behavior-driven development (BDD) is frequently misunderstood. In reality, both approaches have advantages and disadvantages to consider. 

TDD vs BDD, which is perfect for you?

In this article, we’ll look at TDD vs BDD and see how they can complement each other.

Behavior-driven development is frequently misunderstood, but it is simply the next step in the evolution of test-driven development.

What is TDD?

TDD is a development technique that focuses more on implementing a software application/product feature. 

It primarily refers to writing a test case that fails because the specified function does not exist and then updating the code to allow the test case to pass, resulting in the feature being implemented in the system. 

Test-Driven Designing and creating tests for each minor aspect of an application’s functionality is the first step in development. The TDD framework tells programmers to write new code only if an automated test fails. This prevents code duplication. 

So to start the discussion of TDD vs. BDD, let us first see both TDD and BDD separately. Let’s look at what, how (process), and why (benefits) of TDD and BDD.

What is BDD?

A development method called behavior-driven development (BDD) places more emphasis on the behavior of a software application. 

The process primarily involves creating an executable specification that fails because the required feature isn’t present. It is followed by writing the simplest possible code to enable the specification to succeed and, as a result, implementing the desired behavior in the system. 

In reality, it is a team methodology in which developers, customers, and QAs participate.

Now that you know what TDD and BDD are let’s move further with our discussion on TDD VS BDD and see the process of both of these methods.

Process of TDD

#01 Perform A Test To See Whether It Fails

In order to implement the test, create a unit function. Only one behavior of the function should be the focus of the brief test, which shouldn’t last too long. 

Write the bare minimum of requirements-compliant code. The test should now be run to see if it fails.

When a test yields a negative result, you know you’re doing it right, and it wasn’t just beginner’s luck. So it’s better to fail here.

#02 Craft The Appropriate Code To Produce A Successful Outcome

Write the bare minimum amount of supporting code required to pass the test. Move on if the code is accepted. Repeat the test to make sure it passes.

#03 Refactor Till Needed

Once the test has been passed, begin refactoring without dividing the code. To make sure the code is clean, evaluate it and look for areas that could be improved. By adding new features, duplicate code can be eliminated. Enhance the design system to strengthen your solutions.

TDD VS BDD 600 × 600

Process of BDD

The BDD process’s discovery, formulation, and automation phases are where the acceptance criteria are converted into acceptance tests, which are then automated.

#01 Discovery

When writing a story or feature, the Product Owner or Product Manager establishes acceptance criteria as the first step in the process. Team members also find and contribute new criteria as part of the collaborative discovery process. 

For example, a backlog item’s formulation phase solidifies acceptance criteria by producing acceptance tests as it approaches implementation. Initial acceptance standards are frequently explained in vague, general terms.

#02 Formulation

We formulate each example as structured documentation once we have drawn at least one useful example from our discovery sessions. This provides us with an easy way to verify that we do, in fact, have a common understanding of what to construct.

The formulation phase clears up these ambiguities by transforming the scenarios into thorough acceptance tests that are precise, transparent, and unambiguous examples of behavior.

#03 Automation

The acceptance tests are automated during the automation phase, allowing them to run continuously and verify that the system invariably supports the new behavior. Instead of just writing tests, BDD aims to express requirements in clear terms.

The outcome is the same whether it is seen as a test or as an expression of requirements. Acceptance tests serve to document the choices made during the team’s discussion with the product owner so that the team is aware of the precise intended behavior.

Benefits of TDD

Till now, in our discussion of TDD VS BDD, we have seen the what and how (process) of TDD and BDD in detail. 

Now let’s examine the individual benefits of both TDD and BDD to make the decision of TDD VS BDD much easier for you.

#01 You Only Write The Necessary Code.

When all of your tests are successful, you must refrain from writing production code as per the principles. 

For example, you would like a test to drive the implementation of the feature if your project requires it. The code you create is as straightforward as it can be. Thus, all the code included in the final product is needed to implement the features.

#02 More Modular Design

One micro feature is considered at a time in TDD. Additionally, the code automatically becomes simple to check because the test is written first. 

Therefore, code with a clear interface is simple to check. This results in your application having a modular design.

#03 Easier To Maintain 

Because the various parts of your application are decoupled from one another and have clear interfaces, the code becomes easier to maintain. 

For example, you can replace the implementation of a microfeature with a far better implementation without affecting another module. 

You can even keep the tests and rewrite the entire application. Your job is done when all the tests pass.

#04 Early Detection Of Bugs

Although developers test their code, in the world of databases, this frequently takes the form of manual tests or one-off scripts. 

Using TDD, you can create a library of automated tests that you and other developers can run whenever necessary.

#05 Easier To Refactor 

Each feature has been thoroughly tested. You don’t have to be afraid to make drastic changes because everything is fine if all of the test pass. This is critical right now because you, as a developer, are constantly improving your skills. 

If you return to the project after six months of working on something else, you will most likely have many ideas for improving the code. 

However, your memory of all the various parts and how they fit together is no longer fresh. As a result, making changes is frequently risky. You can quickly improve the code with an entire test suite without fear of breaking your application.

#06 Tests Document The Code. 

The test code demonstrates how your code should be used. As a result, it provides documentation for your code. The test code is a sample code that explains what the code does and how the interface must be used.

#07 Early Bug Notification

Although developers test their code, in the world of databases, this frequently takes the form of manual tests or one-off scripts. Using TDD, you can create a library of automated tests that you and other developers can run whenever necessary.

#08 Project Costs Decrease And Increase In ROI

You can produce high-quality software more quickly by putting test-driven development at the center of your workflow. However, there is less rework, and it is more cost-effective when there are fewer bugs because less time is spent debugging and developing new features.

Too many benefits of TDD, right? But we will recommend you not to hurry to decide the winner between TDD VS BDD so early…

Benefits of BDD

#01 Clarity

Every scenario focuses on a distinct subject. The language used to describe behaviors is simple, and any ambiguity can be resolved with a straightforward conversation.

There is no mysterious technical jargon, unintelligible code, or telephone game. Clarity guarantees that the customer receives what they desire.

#02 BDD Is Intended To Streamline The Development Process. 

The same scenarios are used by everyone involved in development. There is no need to write any additional artifacts because scenarios serve as requirements, acceptance criteria, test cases, and test scripts all in one. 

The modularity of Gherkin syntax speeds up the creation of test automation. The steps to reproduce failures for defect reports can also be used with scenarios.

#03 Artefacts

As a result of the BDD process, scenarios form a collection of self-documenting test cases. This ever-expanding collection makes an ideal regression test suite. 

Scenarios can be run manually or automatically. Any tests that have not yet been automated can be added to a backlog for future automation.

#04 Automation

BDD frameworks for automation make it simple to convert scenarios into automated tests. The scenarios provide the steps, and the automation engineer only needs to write a method/function to perform the operations of each step.

#05 Test-Driven

TDD has evolved into Test-Driven BDD. Writing scenarios from the start instils a quality-first and test-first mindset. BDD automation can fail scenarios until the feature is implemented and tests passes.

#06 Code Reuse

Steps from Given-When-Then can be applied to different scenarios. Each step’s fundamental implementation stays the same. As a result, the code used for automation becomes very modular.

#07 Parameterization

To make scenario steps even more reusable, they can be parameterized. For example, an action like clicking a button might involve entering its ID. 

When creating scenarios, parameterization encourages more constructive discussion and can assist a team in adopting a standard, reusable set of steps.

#08 Variation

It is simple to run the same scenario with various input combinations when using scenario outlines. This is a straightforward but effective method for increasing test coverage without the code duplication that plagues test automation.

#09 Momentum

As more step definitions are added, BDD has a snowball effect, making it simpler and quicker to write and automate scenarios. However, common steps are found in most scenarios. 

For example, sometimes, all that is required to create new scenarios is a single new line or different step parameters.

#10  Adaptability

As the product changes, updating BDD scenarios is simple. Editing is simple in plain language. Automation code changes are safer with a modular design. To choose which scenarios execute and which do not, scenarios can also be filtered by tag name.

Phew, too many benefits of BDD as well! So, now what’s your opinion – which one can be the winner in TDD VS BDD?

Unable to conclude? No worries, let’s discuss the key differences between TDD VS BDD.

Key Differences: TDD vs BDD

  • Since BDD is written in English, it is easier for all stakeholders to understand.
  • In TDD, test cases are written in programming languages like Ruby and Java.
  • TDD is concerned with implementing functionality
  • BDD explains an application’s behavior to the end user. Compared to TDD, BDD can more easily accommodate changes in functionality.
  • In contrast to TDD, BDD allows all the stakeholders to agree on the requirements, which makes acceptance simple.
  • The core concept of BDD is the application’s behavior; it puts the customer first and encourages developers and testers to put themselves in the customer’s shoes. 

For example, BDD might not accurately represent a situation where actions do not have an impact on the end user. If so, TDD is more effective for the goal.

It may not be possible to determine what works for every project universally, like with many other software development methodologies. 

For example, BDD serves as a useful tool to record all user actions for systems that are driven by end-user actions, like an HR system or an e-commerce website. For example, TDD might be the better option for systems that have third-party API calls, cron jobs, or data exports/imports.

So now, after knowing the key differences, we are pretty sure that you can see that you can’t state any winner between TDD VS BDD because, with the needs and usability, you have to either switch or use both of them in a go.

What’s The Difference between TDD and BDD?

Since both BDD and TDD are testing approaches for software applications, they may appear to be very similar. In both situations, the developer creates the test first and then writes the code to pass it. 

Additionally, the tests in both situations can be used as a component of an automated testing framework to stop bugs.

Differential FeaturesTDDBDD
Tests you’re performingTDD is geared toward testing isolated, smaller pieces of functionality.The TDD test in the previous example asserts the outcome of a specific method.BDD is intended to test an application’s behavior from the end user’s perspective. BDD test only considers the outcome of the higher-level scenario
How are you testing?Carried out by a lone developer without the assistance of product managers or other stakeholders.Product managers, developers, and test engineers work together in BDD to generate specific illustrations of desirable functionality. Before any implementation, there is a lot of communication. 
How do they work together?
(It’s crucial to remember that BDD and TDD aren’t incompatible)
Many Agile teams employ TDD without also utilizing BDD. BDD ensures that most of the application’s use cases function at a higher level and offer higher confidence.
Implementation DifferencesAgile development companies have widely embraced test-driven development, and various tools are available to aid team collaboration. There aren’t as many tools available for behavior-driven development because it requires collaboration between technical and business teams.
The test is a BDD test management system created to fill the gap and simplify continuous testing. 

Some important things to note:

Business teams can define and update features with ease thanks to scenario editors that are simple to use, and writing tests is made more accessible thanks to integrations with automation frameworks and CI/CD pipelines.

The plain-text language in the features and the aggregated data from the integrations contribute to the creation of documentation that can be referred to at any time by technical or business teams. 

For instance, business users can ensure that a specific feature was developed and is still operational as of the most recent CI run.

The excellent news about BDD is that it doesn’t necessitate reworking any existing TDD practices—it simply requires you to invest in a little more communication, which can pay off in the form of less ambiguity and greater product confidence.

Difference between TDD VS BDD

Behavior Driven DevelopmentTest Driven Development
A development method called “behavior-driven development” emphasizes the behavior of a software application.
Participants in BDD include developers, customers, and QAs.
The process primarily involves creating an executable specification that fails because the required feature isn’t present, followed by writing the most straightforward possible code to enable the specification to succeed and, as a result, implementing the desired behavior in the system.
System requirements are its main area of interest.
In BDD, a scenario serves as the initial input.
Here, behavior and scenarios are written in simple English.
Collaboration between all stakeholders is necessary for BDD.
It is a sound strategy for projects whose development is influenced by user actions.
Tools like Cucumber, Dave, JBehave, Spec Flow, Concordian, BeanSpec, etc., are used.
Using the test-driven development methodology, a software application’s or product’s implementation of a feature is given more attention.
Participants in TDD are programmers.
It mainly involves writing a test case that fails because the desired functionality isn’t present, updating the code to make the test case pass, and then adding the desired functionality to the system.
Unit testing is its main focus.
The test case serves as the TDD starting point.
It is a technique for development.
The language used here is comparable to the programming language used for feature development.
Collaboration is only necessary between developers when using TDD.
It is a sound strategy for projects involving third-party APIs.
JBehave, JDave, Cucumber, Spec Flow, BeanSpec, FitNesse, etc., are a few of the tools used.

Read also: Emulators vs. Real Devices For Test Automation: Which Is Better?


Over the last few years, test-driven development has become the standard approach for Agile software development. 

The approach reduces the number of bugs that reach production and ensures that software can be released without interruption.

Beyond TDD, behavior-driven development represents an evolution in which business goals can be communicated to developers more effectively. 

BDD reduces confusion about acceptance criteria by bridging the gap between business and technical teams, identifies potential problems with user stories early, and ensures that the application functions as expected for end users.

The decision between TDD VS BDD depends on the organization and the application. 

For example, if a team is already using TDD, they may want to try BDD on a small feature to see how it adds value to their process.

And hence even though the discussion on TDD VS BDD is not invalid, but is really very specific to a particular user or organization and their needs.

Generalizing a winner between TDD VS BDD will only limit the possibilities we can achieve by switching or using them simultaneously based on our requirements.

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