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Test Driven Development and TDD Testing

Navdeep Singh Gill | 31 October 2022

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What is Test Driven Development?

Software testingplays a vital role in the life cycle of software and Test Driven Development. It is imperative to identify bugs and errors during software development and increase the quality of the product. Therefore, one must focus on software testing. There are many approaches, and Test Driven approach is one of them. It is a key practice for extreme programming; it suggests that the code is developed or changed exclusively by the unit testing. TDD is a software-driven process that includes test-first development. It means that the developer first writes a fully automated test case before writing the production code to fulfill that test and refactoring. It is a practice of writing a (failing) test before writing the code of a feature. Feature code is refined until it passes the unit test.

TDD and Agile

The TDD approach originates from the Agile manifesto principles and Extreme programming. As the name suggests, the test process drives SDLC. Moreover, it’s a structuring practice that allows developers and testers to obtain optimized code that proves resilient in the long term. Agile development demands frequent feedback to develop the expected outcome. In simple terms, one can also term Agile development as Feedback Driven Development.

Unit Testing is a modular approach followed in testing, single-single functionality or part of the code tested without waiting for other of code to be completed. - From the Article, Unit Testing Techniques and Best Practices

Steps for the same are given below –

  • Firstly, add a test.
  • Run all the tests and see if any new test fails.
  • Update the code to make it pass the new tests.
  • Rerun the test and if they fail, then refactor again and repeat.

Benefits for  Test Driven Development and TDD Testing?

TDD is a programming technique that enables the developer to take a small step during building software. It gives a way to think through one's requirements or design before the developer writes functional code. Consider an example, developer write some code, then compile it, and then test it. Maybe there are chances of failure. In this case, it becomes easy to find and fix those defects if a developer had written two new lines of code than a thousand. TDD is most efficient and attractive way to proceed in smaller steps.

Below are the benefits of TDD

  • Development expenses are reduced
  • Improved Code Quality
  • Quality is enhanced
  • Shortened Time to Market
  • More productive as compared to attempting to code in giant steps.
  • Fewer Bugs.
  • Higher quality software.
  • Focus on single functionality at a given point in time.
RPA is an automation technology in which RPA developers automate repetitive, manual business processes through different RPA tools. Source:  RPA Testing Methodology

How Test driven Development work?

  • Firstly, add a test.
  • Run all the tests and see if any new test fails.
  • Update the code to make it pass the new tests.
  • Rerun the test and if they fail, then refactor again and repeat.

Test Driven Development Workflow

It promotes the idea of each test case testing one piece of functionality at a time. The workflow of it is as follows –
  • Write a concise, minimal test for a new piece of functionality. This test will fail since the functionality isn’t implemented yet (if it passes, one knows that the functionality either already exists or that the test isn’t designed correctly).
  • Implement the new functionality and run all tests, both the new and pre-existing ones. Repeat until all tests pass.
  • Clean up the code and ensure that all tests still pass, then return to step 1.
TDD Workflow

Why TDD Testing  is important?

  • Requirements - Drive out requirement issues early (more focus on requirements in depth).
  • Rapid Feedback - Many small changes Vs. One significant change.
  • Values Refactoring - Refactor often to lower impact and risk.
  • Design to Test - Testing driving good design practice.
  • Tests as information - Documenting decisions and assumptions.

It helps the programmer in several ways, such as -

  • Improve the code.
  • Side by side, increasing the programmer’s productivity.

Using Test-Driven Development concept in one's programming skills -

  • It will save the developer's time which is wasting rework.
  • Able to identify the error/problem quicker and faster.
  • The programmer will write small classes focused only on a single functionality instead of writing the big classes.
  • Whenever the code base gets more prominent, it becomes tough to change and debug the code. Moreover, there is a high chance of mess up of the code.

But, if developers are using its technique -

  • Means developers have automated tests.
  • Writing the test cases for the program is a safe side for the programmers.
  • It becomes easy to view what the error is, where it is and how it is paralyzing one's code.

Need for Test-Driven Development

  • Ensures quality – It helps in ensuring the quality by focusing on requirements before writing the code.
  • Keeps code neat and tidy – It assists in keeping the code clear, simple, and testable by breaking it down into small achievable steps.
  • Maintains Documentation – It provides documentation about how the system works for anyone coming into the team later.
  • Repeatable Test and rapid change – It builds a suite of repeatable regression tests and acts as an enabler for rapid change.
Test-Driven Development in Python is an approach in which we build a test first, then fail the test, and finally refactor our code to pass the test. Source: TDD in Python

Best practices of Test-driven Development ?

The best practices adopting TDD testing are below:

Road Map of TDD

  • One of the best practices is to clear out with thought and further break it into the test case. Follow the red-green approach to build the test case.
  • The first step is to create the red test, and after exposing all the problems related to code, make some changes and make it a green test.

Implementation of TDD

  • It is essential to implement both source code and test case separately. For both implementation and testing, there should be two directories. In every programming language, there should be different packages for both.
  • For example, in Java, “src/main/java” is beneficial for implementation, and on the other hand, “src/test/java” helps in testing.

Structure of Test Driven Development

  • The structure for writing test cases should be correct. It is common practice to write the test class with the same name used in the production/implementation class, but there should be a change in the suffix.
  • Consider an example; if the implementation/production class is “Student,” then the test class should be “StudentTest.” And similarly, in the case of methods, test methods are written with the same name as production methods, but there should be a change in the prefix, like if the method name is “display student name,” then in testing, it should be “testDisplayStudentName.”

Test Driven Development, TDD Testing with Scala

Scala is a programming language that combines both object-oriented and functional programming paradigms. Considering functional aspects of Scala, we can define functions of two types –
  • Functions that perform computation and no I/O operations –
    • In general, the developer must focus on writing functions that are free of side effects.
    • If the function does have side effects, those should not affect the results of subsequent tests.
    • Functions that perform I/O operations and no computation –
    • If a function performs less computation and more IO operations, one must consider specific testing frameworks for writing tests for such functions. For example, there is no need to use ScalaTest (a popular testing framework) for such functions.

In scala, tests reside in the project source but are separate from the application code. There are many testing frameworks available with a lot of features. One can choose according to the specific features in the framework. We will consider ScalaTest, a popular testing framework, in this document.

TDD Style Unit Tests with ScalaTest

ScalaTest is a testing framework inspired by JUnit. ScalaTest supports different styles of writing tests, each designed to address specific needs. Some of the testing styles include –

Every member of the team has to follow the same chosen style. Scala test recommends FlatSpec for the unit and integration testing and FeatureSpec for acceptance testing.

How to implement TDD testing with Scala?

Steps to implement test driven development are described below:

Write a test using the FlatSpec style 

import org.scalatest.FlatSpec
class PizzaTests extends FlatSpec {
 val pizza = new Pizza "A new pizza"
 should "have zero toppings" in {
  assert(pizza.getToppings.size == 0)
 "A pizza"
 should "have one topping" in {
  pizza.addTopping(Topping("green olives"))
  assert(pizza.getToppings.size === 1)
 it must "get pizza pricing"

Write just enough code to fail the test

class Pizza {
 private val toppings = new ArrayBuffer[Topping]
 def addTopping(t: Topping) {}
 def removeTopping(t: Topping) {}
 def getToppings = toppings.toList

Execute the “sbt test” command in the project structure

output – SBT Test Outpu for Test Driven DevelopmentRefactor the code

import scala.collection.mutable.ArrayBuffer
case class Topping(name: String)
class Pizza {
 private val toppings = new ArrayBuffer[Topping]
 def addTopping(t: Topping) {
  toppings += t
 def removeTopping(t: Topping) {
  toppings -= t
 def getToppings = toppings.toList

Execute “sbt run.”

Output – Executing SBT Run Command
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What are the best tools for TDD testing ?

There are many tools available for testing and improving the overall design and implementation of the software system. Some of the most common testing tools are below -

JUnit for Unit Tests

Junit is a unit testing framework designed for the Java programming language. Unit tests are the smallest elements in the test automation process. With the help of unit tests, the developer can check the business logic of any class. So JUnit plays a vital role in the development of a test-driven development framework. It is one of the families of unit testing frameworks collectively known as the JUnit originating with SUnit.


Apache JMeter may be used to test performance both on static and dynamic resources, Dynamic Web applications (Mainly for Load/Performance testing). It is beneficial to simulate a heavy load on a server, servers, network, or object to test its strength or analyze overall performance under different load types.

Features of Apache JMeter

Ability to load and performs tests on many different applications/server/protocol types. Some of them are below -

  • Web - HTTP, HTTPS (Java, NodeJS, PHP, ASP.NET)
  • SOAP/REST Webservices
  • FTP
  • Database via JDBC
  • LDAP
  • Message-oriented middleware (MOM) via JMS
  • Mail - SMTP(S), POP3(S), and IMAP(S)
  • Native commands or shell scripts
  • TCP
  • Java Objects

Mockito for Rest API Testing

Its design is like an open-source testing framework for Java which is available under an MIT License. Mockito allows programmers to create and test double objects (mock objects) in automated unit tests for Test-driven Development (TDD). In simple words, Mockito is a framework that developers specifically use to write certain kinds of tests efficiently.

There are also many other tools and frameworks available. It depends on the type of programming language. According to the language, the developer can pick up an appropriate tool and framework for Test Driven Development in Golang.

Holistic Strategy Towards TDD

Test-driven development is a development technique where the developer must first write a test that fails before writing a new functional code. It ensures a proven way to ensure effective unit testing; however, it does not replace traditional testing. We believe that TDD is an excellent practice that all software developers should consider during the development process.