Black-box testing techniques in Software Engineering - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is black-box testing?

Black-box testing is a software testing method where the tester evaluates the functionality of an application without looking at its internal code or structure. The focus is on inputs and expected outputs.

beginner

Name three common black-box testing techniques.

Three common black-box testing techniques are equivalence partitioning, boundary value analysis, and decision table testing.

beginner

What is equivalence partitioning in black-box testing?

Equivalence partitioning divides input data into groups that are expected to be treated the same by the software. Testing one value from each group helps reduce the number of test cases while covering possible inputs.

beginner

Explain boundary value analysis.

Boundary value analysis tests the values at the edges of input ranges because errors often occur at these boundaries. For example, if input is valid between 1 and 10, tests would include 1, 10, and values just outside this range.

intermediate

What is decision table testing?

Decision table testing uses a table to represent different combinations of inputs and their corresponding expected outputs. It helps test complex business rules by covering all possible conditions.

Which of the following is NOT a black-box testing technique?

A Code coverage analysis

B Boundary value analysis

C Equivalence partitioning

D Decision table testing

Code coverage analysis is a white-box testing technique because it requires knowledge of the internal code.

In black-box testing, what is the main focus?

A Internal code structure

B User interface design

C Database schema

D Input and output behavior

Black-box testing focuses on checking if the software behaves correctly for given inputs and produces expected outputs.

Which black-box technique helps reduce the number of test cases by grouping inputs?

A Boundary value analysis

B Equivalence partitioning

C Decision table testing

D State transition testing

Equivalence partitioning groups inputs that should be treated the same, reducing test cases.

Boundary value analysis tests values:

A At the edges of input ranges

B Only in the middle of input ranges

C Randomly selected

D Only invalid inputs

Boundary value analysis focuses on testing inputs at the edges where errors are more likely.

Decision table testing is especially useful for:

A Simple input fields

B Code debugging

C Complex business rules

D Performance testing

Decision tables help test all combinations of conditions in complex business rules.

Describe the main idea behind black-box testing and why it is useful.

Think about testing like a user who only sees the software interface.

Explain how equivalence partitioning and boundary value analysis help create effective test cases.

Consider how testers pick inputs to cover many cases without testing everything.

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