Why Error guessing in Testing Fundamentals? - Purpose & Use Cases

The Big Idea

What if you could guess where bugs hide before testing even starts?

The Scenario

Imagine testing a new app by clicking randomly, hoping to find bugs. You try some obvious steps but miss many hidden errors because you don't know where to look.

The Problem

Manual random testing is slow and misses many bugs. It's like searching for a needle in a haystack without a magnet. You waste time on safe areas and overlook risky parts.

The Solution

Error guessing uses experience and intuition to guess where bugs might hide. It guides testing to focus on tricky spots, making bug finding faster and smarter.

Before vs After

✗ Before

Test random inputs without plan
Check only main features

✓ After

Focus tests on known weak spots
Try inputs that caused bugs before

What It Enables

Error guessing lets testers find hidden bugs quickly by targeting risky areas based on past knowledge.

Real Life Example

A tester remembers that entering special characters caused crashes before, so they try those inputs first to catch errors early.

Key Takeaways

Manual random testing is slow and misses bugs.

Error guessing uses experience to focus testing.

This approach finds bugs faster and smarter.

Practice

1. What is the main idea behind Error guessing in software testing?

easy

A. Using formal test cases only

B. Writing automated tests for every function

C. Guessing where errors might occur based on experience

D. Ignoring past bugs and testing randomly

Solution

1. Step 1: Understand the concept of error guessing

   Error guessing is a technique where testers use their experience to predict where bugs might be.

2. Step 2: Compare options with the concept

   Only Guessing where errors might occur based on experience matches the idea of using experience to guess errors, others describe different testing methods.

3. Final Answer:

   Guessing where errors might occur based on experience -> Option C

4. Quick Check:

   Error guessing = Experience-based bug prediction [OK]

Hint: Error guessing is about experience, not formal rules [OK]

Common Mistakes:

• Confusing error guessing with automated testing
• Thinking error guessing ignores tester knowledge
• Believing error guessing is random testing

2. Which of the following is a correct example of an error guessing test case?

easy

A. Test all buttons for correct color

B. Test the software without any plan

C. Test only the homepage layout

D. Test input with empty fields to check validation

Solution

1. Step 1: Identify error guessing test case traits

   Error guessing focuses on inputs or actions likely to cause errors, like empty fields.

2. Step 2: Evaluate each option

   Test input with empty fields to check validation tests empty input, a common error source. Others are unrelated or random.

3. Final Answer:

   Test input with empty fields to check validation -> Option D

4. Quick Check:

   Empty input tests = Error guessing [OK]

Hint: Look for tests targeting likely error spots [OK]

Common Mistakes:

• Choosing tests unrelated to error conditions
• Confusing UI checks with error guessing
• Selecting random or unplanned tests

3. Given this scenario: A login form accepts username and password. Which input is best for error guessing?

medium

A. Username: 'admin', Password: '1234'

B. Username: '', Password: ''

C. Username: 'user1', Password: 'password'

D. Username: 'test', Password: 'test123'

Solution

1. Step 1: Identify inputs likely to cause errors

   Empty username and password fields often cause validation errors.

2. Step 2: Compare options for error likelihood

   Username: '', Password: '' uses empty inputs, which is a common error guess. Others are normal inputs.

3. Final Answer:

   Username: '', Password: '' -> Option B

4. Quick Check:

   Empty inputs = Common error guess [OK]

Hint: Empty or invalid inputs are classic error guesses [OK]

Common Mistakes:

• Choosing normal valid inputs
• Ignoring empty or boundary inputs
• Assuming random inputs are best

4. You wrote an error guessing test for a form but it never finds bugs. What is the most likely problem?

medium

A. You guessed errors in unlikely places

B. You wrote too many test cases

C. You automated all tests

D. You tested only the UI colors

Solution

1. Step 1: Understand error guessing effectiveness

   Error guessing works best when testers guess likely error spots based on experience.

2. Step 2: Analyze why tests fail to find bugs

   If guesses are in unlikely places, bugs won't be found. Other options don't explain this well.

3. Final Answer:

   You guessed errors in unlikely places -> Option A

4. Quick Check:

   Wrong guess spots = No bugs found [OK]

Hint: Guess where errors usually happen, not random places [OK]

Common Mistakes:

• Thinking more tests always find more bugs
• Believing automation replaces error guessing
• Focusing on UI style instead of error sources

5. You want to use error guessing to test a calculator app. Which combination of inputs is best to find errors?

hard

A. Very large numbers, zero, and dividing by zero

B. Random letters instead of numbers

C. Only positive integers

D. Normal numbers like 5 + 3, 10 - 2

Solution

1. Step 1: Identify error-prone inputs for calculator

   Calculators often fail with large numbers, zero, or division by zero.

2. Step 2: Evaluate options for error guessing effectiveness

   Very large numbers, zero, and dividing by zero targets these error-prone inputs, while others do not or are invalid inputs.

3. Final Answer:

   Very large numbers, zero, and dividing by zero -> Option A

4. Quick Check:

   Edge and invalid inputs = Best error guesses [OK]

Hint: Test edge cases and invalid inputs for errors [OK]

Common Mistakes:

• Testing only normal inputs
• Ignoring division by zero errors
• Using completely invalid inputs without context