📘 GREY BOX TESTING TECHNIQUES

✅ 1. What is Grey Box Testing?

Definition: Grey Box Testing is a technique where the tester has partial knowledge of the internal code or system design, but testing is mainly done from the user (external) perspective.

👉 Simple meaning: It is a combination of Black Box + White Box Testing.

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🎯 Key Features

• Partial knowledge of code (not full access)

• Tests both:

  • Functionality (like black box)
  • Internal logic (limited, like white box)

• Focus on data flow and integration

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📦 Basic Working

Input → System → Output
          ↑
   Partial knowledge of code

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🔑 WHY USE GREY BOX TESTING?

• To find hidden defects missed by black box testing
• To improve test coverage
• To test complex systems efficiently

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🧪 MAIN GREY BOX TESTING TECHNIQUES

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🟢 1. MATRIX TESTING

📌 Definition:

Tests the relationship between input variables and output results.

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🪜 Steps:

1. Identify all variables
2. Create a matrix of inputs vs outputs
3. Design test cases for combinations

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📊 Example:

Login system:

Input	Output
Valid username + valid password	Success
Invalid username	Error
Invalid password	Error

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🎯 Key Point:

• Focus on data mapping
• Useful in database applications

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🔵 2. REGRESSION TESTING (Grey Box Perspective)

📌 Definition:

Testing done after code changes to ensure existing features still work correctly.

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🪜 Steps:

1. Modify code
2. Re-run previous test cases
3. Check for failures

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📊 Example:

• Add new feature → test old login system again

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🎯 Key Point:

• Ensures no new bugs are introduced

👉 🔥 Frequently asked!

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🟡 3. PATTERN TESTING

📌 Definition:

Testing based on known defect patterns or past errors.

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📊 Example:

• If system failed earlier with invalid input, test similar cases again

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🎯 Key Point:

• Uses experience + system knowledge

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🟣 4. ORTHOGONAL ARRAY TESTING

📌 Definition:

A technique to test multiple input combinations efficiently using minimum test cases.

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🪜 Steps:

1. Identify input parameters
2. Select representative combinations
3. Execute tests

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📊 Example:

Instead of testing all combinations:

• Use selected combinations that give maximum coverage

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🎯 Key Point:

• Saves time
• Reduces number of test cases

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🟠 5. DATABASE TESTING

📌 Definition:

Testing database operations like:

• Data storage
• Retrieval
• Integrity

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📊 Example:

• Check if login data is correctly stored in database

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🎯 Key Point:

• Verifies backend logic

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🔴 6. API TESTING (Grey Box)

📌 Definition:

Testing Application Programming Interfaces (APIs) with partial knowledge of system logic.

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📊 Example:

• Sending request → checking response
• Validating data exchange

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🎯 Key Point:

• Tests communication between systems

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🧠 IMPORTANT CHARACTERISTICS

• Combines advantages of both testing types

• Focus on:

  • Data flow
  • Interfaces
  • Integration

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⚖️ ADVANTAGES & DISADVANTAGES

✅ Advantages:

• Better test coverage than black box
• Does not require full code knowledge
• Efficient for large systems

❌ Disadvantages:

• Requires technical knowledge
• Limited access to code
• Test design can be complex

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🔥 FREQUENTLY ASKED EXAM POINTS

✔ Define Grey Box Testing ✔ Difference between Black, White, Grey Box ✔ Regression Testing explanation ✔ API Testing concept ✔ Advantages & disadvantages

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📊 QUICK REVISION TABLE

Technique	Purpose	Key Idea
Matrix Testing	Input-output relation	Data mapping
Regression Testing	After changes	Re-test system
Pattern Testing	Past defects	Error patterns
Orthogonal Array	Reduce test cases	Efficient combinations
Database Testing	Backend data	Data integrity
API Testing	System communication	Request-response

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🎯 FINAL SUMMARY

• Grey Box Testing = Black Box + White Box

• Tester has partial system knowledge

• Focus on:

  • Data flow
  • Integration
  • Backend systems

• Important techniques:

  • Regression Testing (very important)
  • API Testing
  • Database Testing

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🧾 FINAL COMPARISON (ALL TESTING TECHNIQUES)

Feature	Black Box	White Box	Grey Box
Code Knowledge	❌ No	✅ Full	⚠️ Partial
Focus	Functionality	Logic	Both
Complexity	Low	High	Medium
Performed By	Testers	Developers	Both
Coverage	Limited	High	Balanced

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