API Testing with Rest Assured

1. What is REST?

• Rest or Representational State Transfer is a Java Library or Java API for testing Restful Web services.
• Rest is used to run or invoke REST web services and validate response
• Used to test XML or JSON based web services.
• Supports HTTPS method like GET, POST, PUT, DELETE, OPTIONS, PATCH AND HEAD
• Can integrate with TestNG or Junit.
• Rest is implemented in Groovy

2. What is Groovy?

• Groovy is a JVM-based dynamic language that is fully compatible with Java. It is used in Jenkins pipelines, Gradle build scripts, and frameworks like Spock.

Prerequisites

• Language - Java
• IDE - VS code
• Dependency Management Tool - Maven
• Framework - TestNG

Helpful Tools

• JSON Path Finder

Maven Dependencies

• io.rest-assured
• org.testng
• com.googlecode.json-simple

Website for Testing

• Dev community
• Reqres

How to set API key in REQRES in Windows?

• Create an account in Reqres
• Go to API Key
• Create New API key and give this a name
• Copy the API key and save it in local
• Open CMD and paste the following command
  • setx REQ_RES_API_KEY="**YOUR_API_KEY**"
• Close CMD and rerun
• Use command echo %REQ_RES_API_KEY% and check if you get your API key
• Now create a "EnvironmentConfig.java" file and add the details of API Key in it
• And all set!!

Local Server Setup

• Check if you have npm and node.js package installed in cmd and if not then install it
  • npm -v -> Check the npm version
  • node -v-> Check the node.js version
• Run cmd as Administrator and paste the cmd : npm install -g json-server@0.17.4 -> Install the JSON Server in local
• Then paste " json-server --watch db.json -> Starts the JSON server
• You will have db.json created in the directory where you ran the cmd command
• Copy and paste the local host URL: http://localhost:3000/
• Now run and enjoy

Setup JSON Schema Validation

1. Why do we need to JSON Schema Validation? Ans: JSON Schema testing ensures that the API response structure (contract) is correct and stable, independent of the actual data values. It checks:

   • Missing fields
   • Renamed fields
   • Wrong data types
   • Unexpected structure changes This is critical when:
   • Data is dynamic
   • IDs and timestamps change every run

2. What JSON Schema Validation Checks ?

Check	Example
Field existence	id must exist
Data type	id must be integer
Required fields	name, email
Array vs object	users must be array
Nested structure	address.city
Enum values	status ∈ [active, inactive]
Additional fields	Optional / forbidden

3. Setup:

• Goto : JSON to JSON Schema Converter
• Goto: Reqres and copy one of the JSON response
• Paste the response in JSON schema generator
• Goto target/classes and paste the code in schemaUserData.json (This is adding JSON FILE IN CLASSPATH)
• Get the JSON schema Validator Repo and paste in POM file
• Run the code JsonSchemaValidator.java

Points to Remember

• https://api.example.com/users?id=10
  • https: Scheme
  • api.example.com: Host
  • /users: Resource Path
  • id=10: Query String