Black-box testing techniques in Software Engineering - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Equivalence Partitioning

Which of the following best describes the purpose of equivalence partitioning in black-box testing?

A To check the software's performance under heavy load

B To test the internal structure of the software by examining code paths

C To divide input data into groups that are expected to be treated the same by the software

D To verify the software's installation process

💡 Hint

Think about how testers reduce the number of test cases by grouping inputs.

Equivalence partitioning divides input data into classes where all inputs in a class are expected to be handled similarly by the software, reducing redundant tests.

📋 Factual

intermediate

Boundary Value Analysis Purpose

What is the main goal of boundary value analysis in black-box testing?

A To test the software's response to invalid input types

B To test values at the edges of input ranges where errors often occur

C To analyze the software's internal logic for errors

D To check the software's compatibility with different operating systems

💡 Hint

Consider where bugs are most likely to happen in input ranges.

Boundary value analysis focuses on testing inputs at the minimum, maximum, just inside, and just outside boundaries because errors often occur at these points.

🚀 Application

advanced

Applying Decision Table Testing

Given a system that approves loans based on two conditions: income level (high or low) and credit score (good or bad), which test case set correctly represents all possible combinations using decision table testing?

A High income & good credit, High income & bad credit, Low income & good credit, Low income & bad credit

B Income above threshold, Credit score above threshold

C Approve loan, Deny loan, Review loan, Escalate loan

D High income only, Low income only, Good credit only, Bad credit only

💡 Hint

Decision tables list all combinations of conditions to ensure coverage.

Decision table testing creates test cases for every possible combination of input conditions to verify correct system behavior for each.

🔍 Analysis

advanced

Cause-Effect Graphing Analysis

Which statement correctly explains the benefit of cause-effect graphing in black-box testing?

A It documents the internal code structure for developers

B It measures the software's speed under different network conditions

C It automates the generation of user interface layouts

D It helps identify logical relationships between inputs and outputs to design effective test cases

💡 Hint

Think about how cause-effect graphs relate inputs to outputs logically.

Cause-effect graphing visually maps input conditions (causes) to output actions (effects), helping testers create test cases that cover complex logical scenarios.

❓ Reasoning

expert

Choosing the Best Black-box Technique for Complex Input

A software accepts a complex input form with multiple fields, each having specific valid ranges and dependencies. Which black-box testing technique is most suitable to ensure thorough testing of all input combinations and their effects?

A Decision table testing, because it systematically covers all combinations of conditions and actions

B Boundary value analysis, because it tests only the edge values of each input field

C Equivalence partitioning, because it groups inputs into broad categories ignoring dependencies

D Random testing, because it selects inputs without any structured approach

💡 Hint

Consider which method handles multiple conditions and their interactions best.

Decision table testing is ideal for complex inputs with dependencies because it covers all possible combinations of conditions and their corresponding actions, ensuring no scenario is missed.

Practice

1. Which of the following best describes black-box testing?

easy

A. Testing software based on its functionality without looking at the code

B. Testing software by examining its internal code structure

C. Testing only the user interface of the software

D. Testing software performance under heavy load

Solution

1. Step 1: Understand black-box testing definition

   Black-box testing focuses on checking software behavior from the user's perspective without knowledge of internal code.

2. Step 2: Compare options with definition

   Testing software based on its functionality without looking at the code matches this definition exactly, while others describe different testing types.

3. Final Answer:

   Testing software based on its functionality without looking at the code -> Option A

4. Quick Check:

   Black-box testing = Functionality testing without code [OK]

Hint: Black-box tests check outputs, not code details [OK]

Common Mistakes:

• Confusing black-box with white-box testing
• Thinking black-box tests only UI
• Assuming black-box tests check performance

2. Which of these is a common technique used in black-box testing?

easy

A. Equivalence partitioning

B. Code coverage analysis

C. Static code review

D. Memory leak detection

Solution

1. Step 1: Identify black-box testing techniques

   Equivalence partitioning divides input data into groups to reduce test cases, a classic black-box method.

2. Step 2: Eliminate non-black-box options

   Code coverage and static code review require code knowledge; memory leak detection is performance testing.

3. Final Answer:

   Equivalence partitioning -> Option A

4. Quick Check:

   Black-box technique = Equivalence partitioning [OK]

Hint: Black-box uses input grouping like equivalence partitioning [OK]

Common Mistakes:

• Choosing code-based techniques for black-box
• Confusing static analysis with black-box testing
• Mixing performance tools with black-box

3. Consider a function that accepts an integer input from 1 to 100. Using boundary value analysis, which of the following is a valid boundary value?

medium

A. 0

B. 50

C. 1

D. 101

Solution

1. Step 1: Understand boundary value analysis

   This technique tests values at the edges of input ranges, such as minimum and maximum valid inputs.

2. Step 2: Identify valid boundary values

   Valid input range is 1 to 100, so boundaries are 1 and 100. Among options, 1 is a boundary value.

3. Final Answer:

   1 -> Option C

4. Quick Check:

   Boundary value = 1 [OK]

Hint: Test inputs at range edges, not middle or invalid [OK]

Common Mistakes:

• Choosing invalid inputs like 0 or 101 as boundaries
• Picking middle values instead of edges
• Confusing equivalence partitioning with boundary testing

4. A tester wrote these test cases for a login form: empty username, empty password, valid username and password, invalid username. What is missing for good black-box testing?

medium

A. Testing with SQL injection strings

B. Testing with boundary values for input length

C. Reviewing the source code for errors

D. Checking server logs for errors

Solution

1. Step 1: Analyze given test cases

   Tests cover empty and valid/invalid inputs but do not check input length boundaries.

2. Step 2: Identify missing black-box technique

   Boundary value analysis for input length is important to catch edge errors, missing here.

3. Final Answer:

   Testing with boundary values for input length -> Option B

4. Quick Check:

   Missing boundary tests = Testing with boundary values for input length [OK]

Hint: Check input length edges for thorough black-box tests [OK]

Common Mistakes:

• Confusing security tests with black-box functional tests
• Thinking code review is part of black-box testing
• Ignoring boundary value analysis

5. You have a form that accepts age between 18 and 60. Using black-box testing, which set of inputs covers equivalence partitioning and boundary value analysis?

hard

A. 18, 19, 59, 60

B. 18, 30, 60

C. 0, 18, 60, 100

D. 17, 18, 30, 60, 61

Solution

1. Step 1: Understand equivalence partitioning and boundary value analysis

   Equivalence partitioning divides inputs into valid and invalid groups; boundary value analysis tests edges of valid ranges.

2. Step 2: Check options for both techniques

   17, 18, 30, 60, 61 includes invalid low (17), valid boundaries (18, 60), valid middle (30), and invalid high (61), covering partitions and boundaries.

3. Final Answer:

   17, 18, 30, 60, 61 -> Option D

4. Quick Check:

   Both partitions and boundaries = 17, 18, 30, 60, 61 [OK]

Hint: Include invalid, boundary, and normal inputs for full coverage [OK]

Common Mistakes:

• Ignoring invalid inputs in test sets
• Testing only valid inputs without boundaries
• Confusing boundary values with just middle values