Home Artificial Intelligence Handbook API Testing with Postman – A Newbie-Pleasant Information

Artificial Intelligence

Handbook API Testing with Postman – A Newbie-Pleasant Information

April 9, 2025

Introduction

APIs, or Software Programming Interfaces, are the invisible connectors that permit completely different software program techniques discuss to one another.They make it doable for apps to share information, carry out actions, and ship seamless consumer experiences.Whether or not you’re ordering meals or checking maps, APIs are working behind the scenes.On this weblog, we’ll discover what APIs are, how they work, and why they matter.By the tip, you’ll have a transparent understanding of how APIs energy the apps we use day by day.

What’s an API ?

API expands as Software Programming Interface.

API (Software Programming Interface) is a algorithm and protocols that permit completely different software program purposes to speak with one another. It acts as an middleman, enabling one program to request information or companies from one other.

It’s the method of communication between two purposes the place apps could differ of their platforms or by way of expertise.

As an illustration: Entrance-end of the app -> center layer (API) -> Again-end of the app

The center layer is used for each fetching information from the backend and inserting front-end information into the backend.

EXAMPLE: Think about you order meals on Swiggy or Zomato, and you’ll see the supply companion shifting on the map. Google Maps API acts like a helper, giving Swiggy/Zomato all the placement and route particulars they should preserve you up to date.

Forms of API :

We are able to categorize APIs into many classes, however most often, APIs are categorized into two varieties: SOAP and REST.

SOAP (Easy Object Entry Protocol) -> helps solely XML information

REST (Representational State Switch) -> helps many codecs like XML, JSON, HTML

Each are internet companies. (An API on the web is named an online service, and all internet companies are APIs.)

An internet service is an API wrapped in HTTP. An internet service wants a community, whereas an API doesn’t want a community for its operation.

Understanding REST API

REST API (Representational State Switch API) is a sort of internet API that follows the rules of REST, an architectural type for designing networked purposes.

REST APIs use normal HTTP strategies to permit communication between a consumer (e.g., your browser or app) and a server.

HTTP strategies are (GET, POST, PUT, DELETE). We are able to additionally determine it as CRUD operations (Create, Learn, Replace, Delete).

That is how REST APIs work: Request Message -> API -> Response Message.

Instance: Whereas we’re trying to find resorts on some web site, it’s the GET technique; ordering meals is the POST technique; altering the meals is the PUT technique; and cancelling the order is the DELETE technique.

Shopper vs Server: What’s the Distinction?

A consumer is any machine, software program, or software that makes requests to a server to entry or work together with assets or companies. A consumer could be a browser or {hardware} machine that accesses a service made by a server.

The consumer is usually the user-facing element in a client-server structure.

A server is a robust pc or software program system that gives companies, assets, or information to different computer systems or purchasers over a community.

It handles requests from purchasers (resembling browsers or apps), processes them, and sends again the required response or information.

Shopper -> Web -> Server

CLIENT / SERVER ARCHITECTURE :

Shopper-Server Structure is a mannequin utilized in networking the place two distinct entities, the consumer and the server, work together to supply companies or assets.

The structure is categorized as One-Tier Structure, Two-Tier Structure, Three-Tier Structure, and N-Tier Structure.

One-Tier Structure (Single-Tier):

The consumer and the server are on the identical machine or in a quite simple setup the place the consumer accesses an area server.
(Instance: An area database software.)

Two-Tier Structure:

The consumer interacts instantly with the server. That is the commonest mannequin.
(Instance: An internet browser interacting with an online server.)

Three-Tier Structure:

The structure is split into three layers: Presentation Layer (Shopper), Software Layer (Server), and Database Layer (Information Storage). The consumer communicates with the appliance server, which in flip communicates with the database server.

Instance: An internet software the place the consumer interacts with an online server, and the server communicates with a database to fetch information.

Presentation Layer (HTML, CSS, JS) → Software Layer (Java, Python, C++, C#) → Information Layer (MySQL, PostgreSQL, MongoDB)

N-Tier Structure:

An extension of the three-tier mannequin, the place there could be a number of intermediate layers for dealing with particular duties (e.g., a separate authentication server, enterprise logic server, and so on.).
(Instance: Giant-scale enterprise purposes with a number of specialised servers

Understanding API Terminologies: URI, URL, and URN

The fundamental terminologies we have to learn about are URI, URL, and URN.

URI (Uniform Useful resource Identifier):

A URI is a novel string of characters used to determine a useful resource on the web or inside a system.
It supplies a solution to reference or find a useful resource, whether or not it’s a webpage, picture, file, or some other kind of information.
Instance: “http://google.com/articles/articlename” – Google.com alone is the URI (simply an identifier of the area).

URL (Uniform Useful resource Locator):

A URL is a particular kind of URI that not solely identifies a useful resource but in addition supplies the means to find it on the web.
It consists of each the handle of the useful resource and the protocol used to entry it.
Instance: “http://google.com/articles/articlename” – The entire URL (full handle with protocol and area).

URN (Uniform Useful resource Identify):

A URN is a particular kind of URI that uniquely identifies a useful resource by identify inside a selected namespace, with out offering the placement or technique of accessing that useful resource.
Not like a URL, a URN doesn’t embody the handle or protocol to entry the useful resource. As an alternative, it supplies a novel identifier for the useful resource.

Instance: “http://google.com/articles/articlename” – articles/articlename is the URN, also called the endpoint.

Options and Assets in APIs

Characteristic:

A function typically refers to a particular attribute, performance, or functionality of a system, software, or service.

Characteristic is the time period utilized in guide testing to check some performance.

Options are elements that present worth to the consumer and outline the system’s habits or what it could possibly do.

Instance: In a messaging app, options may embody sending messages, creating teams, audio calls, and file sharing.

Useful resource:

A useful resource refers to any entity or object that may be accessed, manipulated, or interacted with inside a system. Within the context of APIs or internet companies, a useful resource sometimes refers to information or objects which can be made obtainable via an API and could be created, learn, up to date, or deleted.

Instance: Product might be a useful resource accessible at: https://api.instance.com/merchandise

Payload in APIs

Within the context of APIs and internet improvement, payload refers back to the information that’s despatched with an HTTP request or response.
It’s the precise content material or message being transmitted from the consumer to the server (or vice versa), which is processed or utilized by the server or consumer.

Payload sometimes refers back to the physique of the HTTP request or response .

TYPES OF PAYLOAD

It’s primarily categorized into two varieties resembling Request Payload and Response Payload.

1.Request Payload: The information you ship within the physique of a request (e.g., when creating or updating a useful resource).

Instance: Sending JSON information in a POST request to create one consumer:

jsonCopyEdit{
  "username": "johndoe",
  "electronic mail": "john@instance.com"
}

2.Response Payload: The information despatched again within the physique of the response (e.g., when fetching information or affirmation of an motion).

Instance: Response Payload of beforehand created consumer:

jsonCopyEdit{
  "standing": "success",
  "message": "Consumer created efficiently"
}

Getting Began with Postman

Postman is a well-liked API testing and improvement device that permits customers to ship requests (like GET, POST, PUT, DELETE) to APIs and think about the responses.

We are able to do the next issues in Postman:

Creating and managing collections of API requests.
Sending requests with customized headers, parameters, and physique information.
Viewing responses in several codecs (JSON, XML, and so on.).
Automating exams with pre-defined scripts.

After putting in Postman, there will probably be an choice named ‘Workspace’. A workspace is an space the place we keep information and save them.

It is going to be saved to our logged-in Gmail ID.

Attempt to create one workspace, and whereas creating it, we have to choose which sort we would like and go along with the API Testing choice.

Collections in Postman

In Postman, a set is a gaggle of API requests organized collectively. A set accommodates various folders and HTTP requests.
Inside the gathering, we are able to create any variety of requests as per our requirement. (Requests are a sort of file we are able to create to carry out HTTP requests.)
We are able to embody pre-request and check scripts, use atmosphere variables, and share collections with groups for collaboration.
We are able to create, edit, delete, and run the gathering.
We are able to additionally create duplicate collections, and we are able to export it.

Main Requests we’re going to use within the assortment:

GET – Retrieve the supply from the information.
POST – Create useful resource on database.
PUT – Replace current useful resource on database.
Patch – Replace partial particulars of useful resource.

Delete – Delete current useful resource from the database.

Understanding HTTP Standing Codes

A standing code is a three-digit quantity despatched by a server in response to an HTTP request. It signifies the results of the request and whether or not it was profitable, encountered an error, or requires additional motion.

200 Sequence:
200 – OK, 201 – Created, 202 – Accepted, 203 – Non-authoritative data, 204 – No content material

400 Sequence:
400 – Unhealthy request, 401 – Unauthorized, 403 – Forbidden, 404 – Not discovered, 409 – Battle

500 Sequence:
500 – Inside server error, 501 – Not applied, 502 – Unhealthy gateway, 504 – Gateway timeout, 599 – Community timeout

Setting Up the Surroundings for API Testing

Pre-Requisites:

1.) NodeJS set up for making a customized API

INSTALL NodeJS from its official web site.

npm – Node Bundle Supervisor additionally comes with NodeJS.

After set up, go to atmosphere variables in your PC and verify whether or not the trail is configured or not.

Additionally, run node --version within the CMD immediate to make sure its set up.

2.) Putting in JSON Server

Run npm set up -g json-server in CMD.

Create one JSON file with some JSON information in it. (This will probably be our customized API)

Run that file in CMD as json-server filename.

Then our customized API will run on localhost (you’ll be able to see the port in CMD), and we are able to carry out HTTP requests through Postman.

What’s JSON ?

JSON is expanded as JavaScript Object Notation.

It’s a light-weight, text-based format used to symbolize structured information. It’s generally used for transmitting information between a server and a consumer in internet purposes, particularly in APIs.

Principally, it was designed for human-readable information interchange. It’s textual content, written with JavaScript notation.

It’s prolonged from the JS language. Extension is .json

Its web kind (MIME) is software/json.

Terminologies:

Strings needs to be written in double quotes and should have curly braces. {"identify":"jhon"}
For quantity information, we don’t want to surround it in double quotes. {"age":30}
If we need to give two values for one key, then now we have to separate them with a comma (it’s an array). → {"cellphone":[123,456]}
Boolean information doesn’t require quotations. → {"boolean":false}. null additionally doesn’t require quotations.
Arrays could retailer primitives → {"information":[1,2,3]}. And arrays having objects imply having all of the codecs like quantity and string.

Submit Response Use Circumstances:

This part accommodates primary data and use circumstances about what we have to validate and know for Handbook API Testing.

All of the use circumstances and scripts are going to be executed within the Submit-response tab within the ‘Scripts’ choice.

Issues we have to validate:-

Standing Code
Headers
Cookies
Response Time
Response Physique

Preliminary Stage Validations and Use Circumstances:

Take this URL for example: https://reqres.in//api/customers?web page=2

‘’https://reqres.in’’ –> Host or Area
‘’api/customers?’’ –> Path Parameters
‘’web page=2’’ –> Question Parameters (after the query mark is called a question parameter)
‘’2’’ –> Useful resource

In Postman, whereas sending requests in JSON format (inside the gathering), we have to choose the ‘Uncooked’ choice below the Physique part.

pm – It’s a Postman library that we’re going to use to jot down scripts.

To write down a check script in Postman, now we have two frequent capabilities: Regular Perform and Arrow Perform.

Regular Perform Syntax:

javascriptCopyEditpm.check("Check Identify", operate() {  
    // assertion;  
});

Arrow Perform Syntax:

javascriptCopyEditpm.check("Check Identify", () => {  
    // assertion;  
});

Within the “Check Identify” area, we are able to write our required texts associated to the motion we’re going to carry out.

Within the “assertion” area, we’re going to write the precise script.

We’ll use this syntax within the Postman Scripts choice whereas utilizing HTTP requests in a set.

1.Testing the only standing code :-

javascriptCopyEditpm.check("standing code is 200", () => {
  pm.response.to.have.standing(200);
});

This syntax will check whether or not the HTTP response will return 200 because the standing code or not.

We are able to change the standing code as per our requirement instead of ‘200’.

2.Testing multiple standing code :-

javascriptCopyEditpm.check("profitable publish request", () => {
  pm.count on(pm.response.code).to.be.oneOf([200, 201]);
});

This syntax will check whether or not the HTTP response will return both 200 or 201.

3.Testing Standing Code Textual content :-

javascriptCopyEditpm.check("standing code is 200", () => {
  pm.response.to.have.standing("created");
});

It would verify if the textual content of the standing code is ‘created’ or not.