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API Testing.

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01

What is API Testing and why is it important?

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API Testing validates Application Programming Interfaces directly at the message layer, verifying functionality, reliability, performance, and security without a user interface.

Key Benefits:

  • Early Detection: Identifies issues before UI development
  • Faster Execution: Quicker than UI-based tests
  • Direct Logic Testing: Tests business logic without UI dependencies
  • Integration Validation: Ensures proper system communication
  • Cost-Effective: Earlier bug detection reduces fix costs
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02

What are the different types of APIs?

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REST APIs: HTTP-based, stateless architecture

  • Most common type using JSON/XML
  • Follows REST architectural principles
  • Simple and widely supported

SOAP APIs: XML-based protocol with formal structure

  • Built-in error handling and security (WS-Security)
  • More rigid but enterprise-friendly
  • Contract-first approach with WSDL

GraphQL APIs: Query language with single endpoint

  • Client specifies exact data requirements
  • Strongly typed schema
  • Reduces over-fetching and under-fetching

WebSocket APIs: Real-time bidirectional communication

  • Persistent connections for live updates
  • Ideal for chat, gaming, or streaming applications
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03

What are the key components to test in an API?

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Request Components:

  • Headers, parameters, and body format validation
  • Input data types and constraints

Response Validation:

  • HTTP status codes and response headers
  • Response body structure and content accuracy

Functional Testing:

  • Business logic correctness
  • Data transformation and processing

Non-Functional Testing:

  • Performance (response times, throughput)
  • Security (authentication, authorization)
  • Error handling and edge cases
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04

Explain the different HTTP methods used in REST APIs

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05

What are the most important HTTP status codes for API testing?

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06

What is the difference between Functional and Non-Functional API Testing?

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07

Compare popular API testing tools

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08

What is data validation testing in APIs?

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Intermediate 10
09

How do you test API authentication mechanisms?

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10

What is idempotency and how do you test it?

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11

What is Contract Testing and why is it important?

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12

How do you implement API mocking for testing?

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13

How do you test API rate limiting?

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14

What performance metrics should you measure in API testing?

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15

How do you test API error handling?

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16

How do you test API response schemas?

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17

What is API versioning and how do you test it?

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18

How do you handle test data management for API testing?

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Expert 3
19

How do you test microservices APIs?

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20

What are common API testing anti-patterns to avoid?

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21

How do you measure API testing effectiveness?

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API Testing cheatsheet

Contents 15 sections · ~5 min skim
  • API Testing Fundamentals01
  • Types of APIs02
  • HTTP Methods & Status Codes03
  • Types of API Testing04
  • API Testing Tools05
  • API Testing Best Practices06
  • Common API Testing Scenarios07
  • API Documentation Testing08
  • Advanced Concepts09
  • Critical Testing Scenarios10
  • API Test Automation Framework11
  • Debugging Tips12
  • + 3 more inside
  • + 9 more inside
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