Table of contents
Elevate Your Software Quality: The Critical Need for Effective API Testing
Introduction
Imagine you are building a house. You check that the doors open and close properly, that the lights go on, and that the windows close. But what if the plumbing is leaky, or the wiring isn’t correct inside the walls? You wouldn’t know what was wrong there, by simply looking at it. In the world of software, API testing is like looking at the plumbing and wiring – it tests the components that are not visible, but are equally important.
APIs (Application Programming Interfaces), are the plumbing and wiring of today’s apps. They connect different pieces of software together, so they all talk to each other properly. Testing these pieces that are not visible shows you that your app is not just visually “appealing,” but functions well too.
Which brings me to you, if you are a new tester, or were looking for a way to practice and learn software testing and API testing, you may want to take a look at a Software Testing Course for new starters. They aim to introduce software testing, right from the ground and for absolute beginners.
What are APIs and how do they work?
Understanding APIs in Simple Terms
Consider an API to be like a translator between two different language-speaking friends. It receives a request from one, translates it, and sends it to the other. When you order online via an app, the app forwards your order information via an API to the restaurant system. Subsequently, the restaurant responds with confirmation via an API as well. APIs allow apps to exchange information without having to know the inner workings of the other side.
Role of APIs in Contemporary Software Architectures
Today’s software is usually created with lots of little pieces known as microservices. One microservice performs a single task, such as dealing with user login or making payments. APIs tie all these pieces together so that they are able to function as one large system. APIs are also the basis for mobile applications and cloud services and enable them to communicate with servers, databases, and other applications in an efficient manner.
What is API Testing?
Definition and Purpose
API testing simply ensures that these software intermediaries (APIs) are doing the job they were designed for. API testing is sending requests to an API and then verifying the responses. Does the API give you the correct result? Does the API handle errors properly? Is the API secure? API testing assists with these questions. Unlike testing the buttons or links of a web page, API testing tests the core logic of what forms the app itself.
Types of API Testing
- Functional Testing: Tests whether the API works as expected. For example, if you send the login request, does the API either successfully/unsuccessfully authenticate?
- Load Testing: Tests how many users or requests the API can handle at once. This can be helpful in determining if the system is working properly under pressure, and making sure it is not slowed by too many requests at one time.
- Security Testing: Tests if the API (and the application) is secure from hackers. Security testing checks the application for weaknesses such as broken authentication or information leaks.
- Validation Testing: Checks that the data sent to the API and the data returned is valid and correctly formatted.
- Error Handling Testing: Checks how the API handles errors, invalid data, or server side errors.
The Challenges of Testing APIs (and how to overcome them)
Working with Changing APIs
APIs change naturally when software evolves, new features are added, and old features are removed or modified, which can break your tests if they expect the previous behavior. To prevent your tests from being broken by changes to an API, you need to ensure that you are always utilizing the latest implementation of the website, or at the least, aim to write your tests in such a way that they are calling the API statically. Using API versioning to create different versions of the API for different clients, allows users to migrate users to the latest release of the API without disturbing their old clients.
Working with Testing Data
When testing your API, you typically need to provide specific data inputs in order to test different scenarios. Using ‘real’ data for your input can be difficult and or dangerous. This is why you often see testers using mock data; this is a realistic representation of ‘real’ data, but not actually ‘real’. Testers can easily use mock servers or data generators to surface a variety of test data without the complexities of using real systems or affecting real user data.
Authentication and Authorization complications
Many APIs will include steps for users to authenticate themselves such as logging in with user name and password, or using an API key or token. Testing these secured APIs can introduce additional complications, as you need to do more than just simply pass in the problem space; you need to securely and correctly pass the authentication credentials as well. It is critical to know how to add authentication into the testing, find tools that can help you do this authentically and eventually grow into complete successful API testing.
Common API Testing Tools
There are a number of tools that support and automate API testing, whether to send requests, parse the responses, automate the tests or trying to simulate real-world usage. A few of the more common ones are:
Postman: A very widely used tool with a GUI interface, makes it good for beginner and intermediate testers. Allows you to write and send and organize API requests, run tests in scripts, and work with multiple environments (e.g., dev, stage, prod). Used in manual, and automation tests.
REST Assured: A Java library, it might be best for testers that want to use code to test. It allows writing full REST API tests, and is friendly with testing frameworks like JUnit and TestNG, so best in CI/CD pipelines and bulk automation tests.
SoapUI: Initially built for SOAP APIs, but can also be used for REST. There is a free version, and a paid version, the paid version has even options for security and load testing. Allows you to set up complex test cases without needing deep programming skills. It is common in enterprise organizations still using SOAP APIs.
JMeter: Originally developed to load test websites, Jmeter can also be used to performance test APIs. It can readily simulate heavy traffic to identify performance related problems and supports a large selection of protocols, so it’s an excellent general purpose tool for stress testing your APIs.
Swagger/OpenAPI: Not testing tools themselves, but provide standardized formats to describe APIs. They generate tests, documentation, and client code automatically to improve collaboration, consistency, and onboarding.
Using these tools together you can automate API testing, either to assist very basic manual testing or for complex scripts to automate large tasks.
Best Practices for Efficient API Testing
Start Early in the Development Cycle (Shift Left)
Don’t wait for the software to be ready to start testing APIs. Test APIs as soon as the first API is built. Earlier testing will allow you to find bugs earlier, which can make them cheaper and more manageable to fix.
Use Automation Purposefully
Using automation for repetitive tests is a must, so you do not have to run the assay manually over and over. Automation speeds testing, and ultimately, it provides a uniform result.
Validate Any Response Thoroughly
Don’t just check that the API responded. Check that it has responded with correct data, status codes, and a response that is within an acceptable time.
Keep Tests Maintainable and Reusable
Write tests that are clear, simple, and maintainable/reusable as the API changes. Avoid hard coding values. Instead, use variables and data-driven approaches.
Mock External Services When Necessary
If your API communicates with third-party systems, and those systems are not available for when you want to test, mock servers are available that allow you to simulate them. Mock servers will keep your tests independent and reliable.
Why API Testing is Crucial to Software Quality
API testing is not a choice; it is a necessary process in order to build quality software. The following are the reasons why testing APIs is crucial:
Ensures Core Business Logic Functions
APIs are the building blocks of most applications. They perform the most significant business logic, such as user logins, payment gateways, retrieving data, etc. If your APIs aren’t doing what they should, then your application can’t do what it should do, regardless of how beautiful the interface is. API testing guarantees that these fundamental functions work as expected to prevent costly errors and dissatisfied users.
Enables Faster Releases with Automation
API manual testing is often a time-consuming and prone-to-error process, particularly for high-pressure Agile or DevOps environments. With automated API tests, developers and test teams are able to rapidly verify that new code does not destroy existing functionality. This faster feedback cycle decreases bugs in production and accelerates the releases and makes it faster for companies to respond to shifting requirements in the market.
Enhances Application Security
APIs often reveal confidential data and main functionality. Without testing, APIs become riddled with security vulnerabilities that attackers exploit to steal data, fake users, or shut down the services completely. API-level security testing identifies issues like broken authentication, data leaks, and injection attacks early on, and assists in safeguarding users and business reputation.
Enhances Performance and Reliability
API testing also involves load and performance testing to see what the system will be like under load. Performance tests make it easier to see weak points where the API could break or degrade but the application is still technically up and running at times of heavy use. End users love a fast and stable API while businesses are not losing business during outages or slow responses.
Minimize Testing Time and Total Expenses
Since APIs change much less than their UIs, API tests are less volatile and more reusable. This ultimately reduces your time and effort repairing broken tests following UI changes. In addition, APIs nearly always have less initialization to perform and finish tests faster compared to user interface tests, saving time and testing resources further reducing expenses.
Maintains Backwards Compatibility as API Versioning
As software changes over time, APIs necessarily end up being changed or extended. Yet there will still be sufficient numbers of older users remaining on earlier versions. API testing guarantees backwards compatibility so that upgrading does not become a hindrance to current users or third-party integrations. Such unproblematic transition is disruption-free and helps preserve trust with partners and users.
Increases Test Coverage Beyond the UI Layer
User Interfaces can only show a fraction of what is happening in the application. API testing extends beyond the user interface layer to verify the data is moving correctly from system to system, integrations are functioning as expected and error handling is being handled. This higher level of test coverage can pick up problems that UI testing cannot, enabling a less buggy and more stable product.
Examples and Case Studies from the Real World
Example 1 - A Fintech Company Improved Uptime
To be more specific, this fintech company was having problems with slow system response times during peak hours or use, which not only impacted users but slowed their transactions and thus lost business. The organization conducted serious logging and API load testing and were able to find and resolve a few bottlenecks. They were able to increase uptime by 40%. This provided various outcomes for the organization including fewer crashes for users, a better experience for the customer, and accommodated less lost business.
Example 2 - Faster Deployment with Automated API Testing
A startup created a social media application and automated all of their API tests. By allowing developers to deploy new features every few days rather than weeks, then once bugs were found before deployment it saved lots of time and improved customer satisfaction.
Conclusion
While API testing doesn’t have the visual indicators of buttons clicks or page loads, it plays an invaluable role in building software that is dependable, secure, and performant. API testing ensures that each invisible part of your app, or its APIs, works flawlessly, enabling your users to have a better experience, and ultimately achieving a satisfied customer as a result.
If you want to learn and develop more of these skills, you should look at starting a Software Testing Course which will include both introductory as well as advanced aspects of API testing. Remember, great software isn’t just about what the user sees or interacts with, it’s about what is happening invisibly behind the curtain.
