11 - API Testing Using Postman

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Understanding APIs

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Teacher
Teacher

Welcome everyone! Today, we’re going to explore the concept of APIs. Can anyone tell me what an API is?

Student 1
Student 1

Isn't it something that allows different software to communicate?

Teacher
Teacher

Exactly! An API, or Application Programming Interface, facilitates communication between software systems. This is especially important in QA to ensure everything is functioning correctly.

Student 2
Student 2

I heard there are different types of APIs. Which ones do we focus on in QA?

Teacher
Teacher

Good question! In QA, we primarily deal with REST APIs, which follow the HTTP protocol and typically return data in JSON or XML format.

Student 3
Student 3

So, what does REST stand for?

Teacher
Teacher

REST stands for Representational State Transfer. It has some important properties; for example, REST APIs are stateless, meaning each call is independent, and they rely on resource-based URLs.

Student 4
Student 4

That helps make it easier to work with them!

Teacher
Teacher

Correct! Let’s summarize: APIs allow communication, and REST APIs are key in QA for their stateless, resource-based nature.

HTTP Methods

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Teacher
Teacher

Now, let's discuss the common HTTP methods used with REST APIs. Can someone list them?

Student 1
Student 1

GET, POST, PUT, and DELETE?

Teacher
Teacher

Exactly! Each method carries a specific function. For example, GET retrieves data, while POST creates new data. Can anyone provide examples of when they might use these methods?

Student 2
Student 2

I would use GET to get all users from an API.

Student 3
Student 3

And I'd use POST to create a new user account!

Teacher
Teacher

Great examples! Remember: GET, POST, PUT, and DELETE form the basis of how we interact with APIs in a RESTful architecture.

Student 4
Student 4

Can you explain the PUT method again?

Teacher
Teacher

Sure! PUT is used to update existing data. For instance, if you wanted to update a user's profile, you would use PUT.

Student 1
Student 1

Okay, that makes sense! It’s all about CRUD operations!

Teacher
Teacher

Exactly! Let's recap: the key HTTP methods are GET, POST, PUT, and DELETE, each serving a unique purpose in API interactions.

Using Postman

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Teacher
Teacher

Next, we’ll look at how to use Postman for sending requests. Have any of you used it before?

Student 3
Student 3

I’ve heard of it but never used it!

Teacher
Teacher

No problem! Postman has a user-friendly interface. You start with the Request Builder where you choose the HTTP method and enter the API URL. Let’s break this down.

Student 2
Student 2

What are the other tabs available?

Teacher
Teacher

Excellent question! There’s the Headers tab for setting headers like Content-Type, the Body tab for including data, and the Params tab for adding query parameters.

Student 1
Student 1

And what do you do with the Send button?

Teacher
Teacher

The Send button executes the request! After sending the request, you can view the response including status codes and the response body.

Student 4
Student 4

Can we look at a real example?

Teacher
Teacher

Absolutely! If you select GET and enter the URL 'https://api.example.com/users', then click Send, you’ll see a JSON response of the users.

Student 3
Student 3

That seems simple enough!

Teacher
Teacher

Reinforcing the key points, Postman’s Request Builder, Headers tab, Body tab, and Response Viewer are crucial for effective API testing.

Assertions in Postman

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Teacher
Teacher

Now, let’s discuss how to write assertions in Postman. What do you think assertions are?

Student 2
Student 2

Are they checks to validate what the API returns?

Teacher
Teacher

That's correct! In Postman, assertions are written in the Tests tab using JavaScript. You can check for things like status codes or specific fields in the response.

Student 1
Student 1

Can you give a sample assertion?

Teacher
Teacher

Sure! For example, to check if the status code is 200, you would write: `pm.test('Status code is 200', function() { pm.response.to.have.status(200); });`

Student 3
Student 3

And how do we check if a specific field exists in the JSON response?

Teacher
Teacher

Great question! You could write something like: `var jsonData = pm.response.json(); pm.expect(jsonData.name).to.eql('Charlie');` This checks that the response contains a field named `name` with the value `Charlie`.

Student 4
Student 4

So, we can automate the validation of APIs!

Teacher
Teacher

Exactly! Assertions are a powerful way to automate response validation, ensuring our APIs function correctly. Let's recap: Assertions in Postman allow you to validate various aspects of the response through JavaScript.

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

API testing is crucial for ensuring the reliability and correctness of applications, and Postman serves as an intuitive tool for testing APIs efficiently.

Standard

As APIs become increasingly vital for application functioning, API testing has emerged as a fundamental practice in quality assurance. Postman simplifies the API testing process, enabling users to send requests, receive responses, and validate data without complex coding. This section covers key API concepts, RESTful architecture, and practical Postman operations, making it an essential read for aspiring QA professionals.

Detailed

API Testing Using Postman

API testing is essential in modern software development as it ensures seamless communication between different software systems. An API, or Application Programming Interface, provides the means for these interactions. In this section, we delve into REST APIs, characterized by their statelessness and resource-based structure, employing common HTTP methods like GET, POST, PUT, and DELETE.

Using Postman: Postman serves as an intuitive graphical user interface tool that allows QA professionals to send HTTP requests and analyze the results efficiently. It features a Request Builder for method selection and URL input, a Headers tab for setting request parameters, and a Response Viewer to analyze outcomes.

Writing Assertions: Users can write JavaScript-based tests in Postman's Tests tab which enable automatic validation of API responses. This includes checking status codes and verifying fields within the JSON response. The section concludes with an API testing checklist and a summary of fundamental concepts, equipping QA professionals with practical knowledge for effective API testing.

Audio Book

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What is an API?

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An API (Application Programming Interface) allows different software systems to communicate with each other. In QA, we primarily test REST APIs which follow the HTTP protocol and return data in JSON or XML format.

Detailed Explanation

An API is a set of rules that lets one software application communicate with another. This is crucial in software development since different applications often need to exchange data and functionalities. For instance, when you use an app to check the weather, that app communicates with a weather service API to fetch current weather conditions. In the Quality Assurance (QA) phase, the focus is mainly on testing REST APIs, which utilize the HTTP protocol—a foundation of the web. These APIs often return data in either JSON (JavaScript Object Notation) or XML (eXtensible Markup Language). JSON is more common today due to its simplicity and ease of use in JavaScript environments.

Examples & Analogies

Think of an API like a waiter in a restaurant. When you place an order, you're communicating your needs (like the dish you want) to the waiter (the API). The waiter takes your request to the kitchen (the server) and brings back your food (the data). Just as the waiter helps you communicate with the kitchen, an API helps different software systems communicate with each other.

Introduction to REST APIs

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🔹 REST (Representational State Transfer) is:
● Stateless: Each call is independent
● Resource-Based: Uses URLs to identify resources
● Uses HTTP methods: GET, POST, PUT, DELETE

Detailed Explanation

REST, which stands for Representational State Transfer, outlines a set of principles for designing networked applications. A key characteristic of REST APIs is that they are stateless, meaning that each request from a client to the server must contain all the information the server needs to fulfill that request. This leads to greater scalability as the server doesn’t need to remember previous interactions. Resources in REST are represented by URLs, which act as unique identifiers for these resources. RESTful API operations are typically performed using standard HTTP methods, such as GET for retrieving data, POST for creating new resources, PUT for updating existing resources, and DELETE for removing resources.

Examples & Analogies

Imagine browsing a library. Each book (resource) has its unique location (URL). When you want a book (GET), you go directly to its location. If you want to place a new book on the shelf (POST), you simply take it and put it there without needing to inform the librarian of previous requests. Each transaction (request) stands alone, which mirrors the stateless nature of REST.

Using Postman to Send Requests

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Postman is a GUI tool used to send HTTP requests to APIs and analyze responses.
🔹 Key Areas of Postman Interface:
● Request Builder: Where you choose the HTTP method and enter the API URL
● Headers Tab: Set request headers (e.g., Content-Type: application/json)
● Body Tab: Provide data for POST, PUT methods (usually JSON)
● Params Tab: Add query parameters
● Send Button: Execute the request
● Response Viewer: View status code, response body, headers, and time

Detailed Explanation

Postman is a widely used graphical user interface (GUI) tool that assists developers and testers in interacting with APIs without needing extensive programming knowledge. The main components of Postman's interface include the Request Builder, where you specify the type of HTTP request (like GET or POST) and the API's URL. The Headers Tab allows you to configure important request headers, such as the format of the data being sent. The Body Tab is where you input data for methods like POST and PUT, often in JSON format. Params Tab is for query parameters that can be included in the API request, while the Send Button lets you execute the request. Finally, the Response Viewer displays important information about the response you get back from the server, such as the status code and data returned.

Examples & Analogies

Think of Postman like a remote control for your TV. The buttons on the remote allow you to change channels (method), adjust volume (headers), and navigate menus (body data), all to interact with your TV (API) smoothly. You press buttons to get the results you want, similar to how you send requests to an API through Postman and receive responses.

Example: Sending a GET Request

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  1. Select GET
  2. Enter URL: https://api.example.com/users
  3. Click Send
  4. View response:
    [
    {
    "id": 1,
    "name": "Alice"
    },
    {
    "id": 2,
    "name": "Bob"
    }
    ]

Detailed Explanation

In this example, we're sending a GET request to an API that retrieves a list of users. We start by selecting the GET method, indicating that we want to retrieve data. After that, we enter the specific URL that points to the resource we want to access—in this case, the user list. Once everything is set, we click the Send button, which dispatches our request to the server. The server responds with data, typically in JSON format, which is displayed on the screen. In this case, we see a list containing two users, each represented by their unique ID and name.

Examples & Analogies

Think of it like ordering books from a library's online catalog. You specify what you want (the GET request), the librarian checks their stock (the server), and returns the list of available books (the JSON response). If you requested users, they appear right there in front of you!

Example: Sending a POST Request

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  1. Select POST
  2. Enter URL: https://api.example.com/users
  3. Go to Body > raw > JSON
  4. Enter:
    {
    "name": "Charlie",
    "email": "charlie@example.com"
    }
  5. Click Send

Detailed Explanation

Here, we illustrate how to create a new user by sending a POST request. First, we select the POST method, indicating that we want to send data to create a resource. Next, we enter the appropriate URL for the user resource. The Body section allows us to specify the data we want to send. We select raw format and indicate that we’re sending JSON data. We enter the name and email of the new user, Charlie. Finally, we hit the Send button to execute the request, which should create the new user in the system.

Examples & Analogies

Imagine adopting a pet from a shelter. You go to the shelter (the API), fill out the application with your details (the JSON data), and hand it to the staff (the server). Once they process your application (you hit Send), you have successfully adopted a new pet (a new user is created).

Writing Basic Assertions in Postman

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Postman allows you to write JavaScript-based tests under the Tests tab to automate validation of response data.
🧪 Common Assertions:
// Status code is 200
pm.test("Status code is 200", function () {
pm.response.to.have.status(200);
});
// Response contains expected field
pm.test("Response has user name", function () {
var jsonData = pm.response.json();
pm.expect(jsonData.name).to.eql("Charlie");
});

Detailed Explanation

In Postman, after sending an API request, you can validate the response using assertions, which are scripts written in JavaScript. This is done under the Tests tab. For example, you can check if the server responded with a status code of 200, indicating a successful request, by writing a simple assertion. Additionally, you can assess whether the response contains expected elements or values; for instance, verifying that the name in the returned JSON matches 'Charlie'. Writing these tests helps automate the validation process and ensures that the API behaves as expected.

Examples & Analogies

Consider this like a quality check after cooking a dish. After preparing the meal, you taste it (validate the response) to see if it meets your expectations—if it’s not too salty or if it has the garnish you like (correct status code and expected fields). This way, you ensure every dish is up to your standard before serving it.

API Testing Checklist for QA

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Test Type Example
Status Code Check for correct HTTP status (200, 201, 400, 404, 500)
Validation
Response Verify fields like id, name, etc.
Body Check
Field Data Type Ensure id is an integer, email is a string
Check
Authorization Send without token and verify 401 Unauthorized
Test
Negative Send invalid data, expect proper error message
Testing

Detailed Explanation

Having a checklist for API testing is essential to ensure comprehensive validation of the API behavior. This checklist might include different types of tests, such as checking the status code to ensure that the API returns the correct HTTP response (like 200 for success). Validation checks ensure that the returned response has all the expected fields, such as user IDs and names. Other checks involve ensuring that the data types in the response are as expected—ID should be an integer, and the email should be a string, amongst others. It is also crucial to test authorization by sending a request without proper authentication and checking for errors (like a 401 Unauthorized). Lastly, conducting negative testing involves sending invalid data to ensure that the API responds correctly with the appropriate error messages.

Examples & Analogies

Think of this as a final inspection before a car leaves the factory. You check the engine status, ensure that all systems work correctly, verify that the color matches the customer's order, and run tests to see if it starts with various key conditions (authorization). This comprehensive quality check ensures that the car meets all specifications before it’s delivered to the customer.

Summary of Key Concepts

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Concept Description
REST API API that uses HTTP methods to access resources
Postman Tool for sending, viewing, and testing API requests
Assertions Scripts to validate status codes, fields, values
Common GET, POST, PUT, DELETE Methods

Detailed Explanation

In summary, REST APIs are crucial for enabling interaction between different systems using standard HTTP methods like GET, POST, PUT, and DELETE. Postman serves as an effective tool for anyone engaged in API development and testing, allowing them to send requests, view responses, and perform rigorous tests on API behaviors. Assertions are scripts that automate the validation of responses, ensuring correctness in the data being returned. Understanding these key concepts forms the foundation for efficient API testing.

Examples & Analogies

Imagine learning to drive. You acquire knowledge about the car (API), practice driving (using Postman), and develop habits of checking safety measures (writing assertions). Each of these components, when mastered, allows you to navigate the roads safely and efficiently—similarly, understanding REST APIs, Postman, and assertions enables effective API interaction and testing.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • API: A set of interface rules for software communication.

  • REST API: An API that uses HTTP methods and is stateless.

  • HTTP Methods: Commands such as GET, POST, PUT, DELETE used to interact with REST APIs.

  • Assertions: Scripts in Postman that validate API response data.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • Using POST method to create a new user by sending JSON data to the API endpoint.

  • Sending a GET request to retrieve data of all users from a given API URL.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • APIs allow software to talk, sending data, it’s quite the walk.

📖 Fascinating Stories

  • Imagine you're a librarian, using a catalog system (the API) to communicate what books (data) are checked out or available. The REST methods are like requests to check, add, or change stats about these books.

🧠 Other Memory Gems

  • Remember CRUD: Create, Read, Update, Delete for the main HTTP methods.

🎯 Super Acronyms

R-E-S-T

  • Resource-based
  • Each request is stateless
  • Standard HTTP methods
  • Transfer of data.

Flash Cards

Review key concepts with flashcards.

Glossary of Terms

Review the Definitions for terms.

  • Term: API

    Definition:

    Application Programming Interface, a set of rules that allows different software applications to communicate with each other.

  • Term: REST API

    Definition:

    A type of API that adheres to REST architectural constraints, allowing interaction via HTTP methods.

  • Term: Stateless

    Definition:

    Each call made to a REST API is independent and does not rely on previous calls.

  • Term: HTTP Methods

    Definition:

    Methods used in HTTP requests, including GET, POST, PUT, DELETE, etc.

  • Term: Assertions

    Definition:

    Conditions or statements made to check the validity of data returned from an API.