Many web-based platforms and Software as a Service (SaaS) organizations have created different Application Programming Interfaces (APIs) to allow their customers to interact with and consume data from the platform on their own terms. APIs typically allow machine-to-machine communication using industry standard languages or file formats. APIs free end users from the confines of using a default interface. Additionally, users can integrate controls and outputs into dashboards and custom applications, as well as automate common functions and procedures.
In order to understand how API load testing services fit into your overall testing needs, we should first establish a basic understanding of what is API testing, why API testing is necessary, and how API testing is performed.
Whether the API is a RESTful application that uses XML or JSON, or a SOAP-based XML container, you should build test scripts that check response times and accuracy of the service. Once you’ve established the responsiveness and the accuracy of the API, it’s important to perform two additional tests on the system – API load testing and stress testing.
- Load testing an API proves that the API, and the underlying infrastructure, can handle an expected number of simultaneous requests.
- Stress testing an API tests the upper limits of simultaneous users by increasing the number of requests up to and beyond the theoretical capacity of the service.
Unlike other tools on the market today, users don’t have to worry about specific hardware or software requirements with LoadView. It’s completely cloud-based, so developers and engineers can focus their time creating, executing, and analyzing their API tests. LoadView is an outstanding API testing tool – from SOAP APIs and REST APIs, to performing other Web API level testing and validation – LoadView has you covered.
API Testing for Performance
There are a number of questions you need to answer when setting up API tests, including:
- Who is your end user or target audience?
- Why are they using your API?
- What is the user trying to achieve with the API?
- How critical is the API to your users?
- What happens if the API is unavailable or unreliable?
- How fast do users expect to receive feedback from the API?
- How will you test each of these assumptions?
Once you’ve answered these questions, build API test cases to verify the needs of each test case are met. Depending on the answers these questions, different types of tests might be necessary to validate the test case assumptions. For example, submitting data to an API might only look for a “successful” response from the API. Likewise, sending a query may elicit certain keywords or values in the response from the server.
The results of API testing also differ based upon the reason for testing. There are many different times during the development process, and even post-production, that you would want to test an API. Each of these instances may need to be setup differently.
Ways to Test APIs
- Integration Testing: Integration testing ensures that new changes to the API do not cause problems/bugs in other modules or system.
- Load Testing: Load Testing ensures the production infrastructure is capable of handling the expected number of simultaneous users accessing the system.
- Regression Testing: Regression testing determines whether any new changes cause negative effects in previously successful tests for existing functionality.
- Security Testing: Security testing attempts to exploit potential vulnerabilities in a system or the underlying framework.
- UI Testing: UI testing makes sure every aspect of the user interface functions as expected by testing every case possible using the GUI to ensure it is successful.
- Functional Testing: Functional testing takes the system requirements and user stories and tests each use case to be sure the system is capable of handling all necessary scenarios.
- Stress Testing: Stress testing is similar to load testing in that it may take common use cases and run many simultaneous instances of the case at the same time. Stress testing takes the test one step further than load testing because it continues to push additional simultaneous users through the system until the system reaches a failure point. Perform stress tests on both a system-wide level, as well as on very specific components of a system.
There are many additional names for tests and types of test that can accomplish additional goals. Due to the nature of Dotcom-Monitor tools, we generally focus more on functional testing and load or stress testing APIs.
What Will You Test in the API?
Now that you’re going to test the API, how will you know if the API has succeeded or failed? You need to design your test cases by specifying parameters such as:
- Input parameters
- Expected resulting outputs
- Maximum time to receive a response
- Parsing inputs
- Error handling
- Proper response formatting
After each new code build, include each test case in a testing script and ensure that it runs successfully. Moreover, include each test case in a scheduled load test to verify that the API can handle simultaneous load.
Why Test APIs Externally?
While testing an API from within your network should theoretically help discover the majority of problems with your system, it’s best practices to perform additional tests emulating the end user experience from outside of your network. External API testing can identify response time averages from the perspective of an end user or third-party system. These average response time values server as a baseline performance metrics to which you can compare future responsiveness. Typically, external testing results are more representative of a customer’s experience than a low latency test from within your firewall. External API tests also can help identify problems that you may not experience while testing behind your firewall.
Why Monitor APIs?
APIs provide secondary interfaces for your application users to interact with a system. For example, if a system must be online 24/7, associated APIs should adhere to a similar Service Level Agreement (SLA). Third-party, external API monitoring is the easiest way to provide a non-biased verification that the API is performing within the SLA requirements. Even after you have built and performed tests to verify the API is working, it’s a best practice to setup ongoing monitoring to verify continuous service. Scripts built to perform load tests on a system are reusable and used to monitor the system throughout the service period.
How Do You Test a REST API?
REST APIs are more common due to the standard of the Resource Description Framework (RDF). Subsequently, more APIs are available for integrating one system with anotherAt their simplest, REST APIs consist of Uniform Resource Identifier (URI) requests, such as GET, POST and DELETE. While the complexity of a given API may be as simple as a single GET request, they are more complicated, requiring secure credentials to authenticate and supplying a list of different commands that can be executed, all with multiple variables.
A basic API test uses GET and POST commands to script authentication, read data from a system, POST new data to the system, and confirm the expected response. Once created, users can re-use them for a single-use test, as well as a load testing.
Learn How to Test SOAP APIs
SOAP APIs are similar to REST APIs. A SOAP API may use a Web Services Description Language (WSDL) to specify the available endpoints and data formats. Brendan Quinn at TechWell wrote a great introductory article with links to resources for getting started testing APIs.
Testing Web APIs
Web APIs are empowering external systems to tie into existing applications every day. For example, most common social media platforms have APIs that are used to connect users of one web application to another. Many platforms utilize multiple APIs to let developers of other applications interact with their own systems.
There are many tools available to perform testing on a web API. LoadView focuses on generating external commands from servers outside your network and validating the responsiveness and effectiveness of the API. For applications that expect to have hundreds of thousands of simultaneous users, simultaneous user load testing is an extremely important component of a web API testing process.
API Testing Automation
While testing APIs is clearly essential for both software and websites, it’s often overlooked. APIs are easy targets for cyber-attackers, which is why continual testing is important. For example, are you sure that your API prevents unauthorized queries or submissions? Are you sure that someone can’t start guessing other user’s authentication tokens? Does your API provide error message when there’s a problem or are these properly hidden? There are a lot of security considerations when it comes to API usage. If you fail to automate testing, user data could be at stake.
How can you fix this problem? Simply by automating your API testing. This allows you to check for security problems without having to remember to test manually. There are a variety of solutions to do this, with Postman being one of the most popular open-source options. If you’re looking for a robust, commercially available option that comes with all of the bells and whistles you’d need for true enterprise API testing, then you should consider LoadView and Dotcom-Monitor’s full suite of automated API testing tools. Not only does the Dotcom-Monitor suite cover REST, SOAP, and other APIs, but it also allows for nearly limitless configuration options and reporting tools. Having access to a testing tool like LoadView can literally change the way you run your website or business. Try LoadView for free today and see how you can automate your API testing in minutes!