Code review as testing in Testing Fundamentals - Test Execution Trace

Test Overview

This test simulates a code review process to check for common coding errors and adherence to best practices before running the code. It verifies that the code meets quality standards and is free of obvious mistakes.

Test Code - PyTest

Testing Fundamentals

def code_review_check(code_lines):
    issues = []
    for i, line in enumerate(code_lines, 1):
        if 'print' in line and not line.strip().endswith(')'):
            issues.append(f"Line {i}: print statement missing closing parenthesis")
        if '==' in line and 'if' not in line:
            issues.append(f"Line {i}: '==' used outside if condition")
        if line.strip().startswith('def') and not line.strip().endswith(':'):
            issues.append(f"Line {i}: function definition missing colon")
    return issues

# Example code to review
sample_code = [
    "def greet()",  # Missing colon
    "    print('Hello world'",  # Missing closing parenthesis
    "x == 5",  # '==' outside if
    "if x == 5:",
    "    print('x is 5')"
]

issues_found = code_review_check(sample_code)
assert len(issues_found) == 3, f"Expected 3 issues, found {len(issues_found)}"

Execution Trace - 8 Steps

Step	Action	System State	Assertion	Result
1	Test starts	Test environment ready with sample code lines loaded	—	PASS
2	code_review_check function is called with sample code	Function processes each line of code	—	PASS
3	Line 1 checked: 'def greet()' missing colon detected	Issues list updated with line 1 issue	—	PASS
4	Line 2 checked: print statement missing closing parenthesis detected	Issues list updated with line 2 issue	—	PASS
5	Line 3 checked: '==' used outside if condition detected	Issues list updated with line 3 issue	—	PASS
6	Lines 4 and 5 checked: no issues found	Issues list remains unchanged	—	PASS
7	Assert that 3 issues were found	Issues list contains 3 items	assert len(issues_found) == 3	PASS
8	Test ends successfully	All checks passed, issues correctly identified	—	PASS

Failure Scenario

Failing Condition: The code review function misses one or more issues or reports incorrect number of issues

Execution Trace Quiz - 3 Questions

What does the test verify about the sample code?

A It runs the sample code and checks output correctness

B It measures the performance of the sample code

C It checks for common syntax errors and coding mistakes before running the code

D It verifies the sample code connects to a database

Key Result

Code review acts as an early testing step to catch errors and improve code quality before actual execution, saving time and reducing bugs.

Practice

1. What is the main purpose of code review in software testing?

easy

A. To find bugs and improve code quality before running the code

B. To write new features faster

C. To deploy code to production immediately

D. To replace automated testing completely

Solution

1. Step 1: Understand code review purpose

   Code review is done to check code manually for errors and improvements before execution.

2. Step 2: Compare options with purpose

   Only To find bugs and improve code quality before running the code matches the goal of finding bugs and improving quality before running code.

3. Final Answer:

   To find bugs and improve code quality before running the code -> Option A

4. Quick Check:

   Code review = find bugs early [OK]

Hint: Code review finds bugs before running code [OK]

Common Mistakes:

• Thinking code review replaces automated tests
• Believing code review speeds up deployment
• Confusing code review with coding new features

2. Which of the following is the correct way to give feedback during a code review?

easy

A. Provide clear, constructive comments with examples

B. Only comment if you find a syntax error

C. Ignore small mistakes to save time

D. Say 'This code is bad' without explanation

Solution

1. Step 1: Understand effective feedback

   Good feedback is clear, constructive, and helps improve code with examples.

2. Step 2: Evaluate options

   Provide clear, constructive comments with examples matches this approach; others are either rude, incomplete, or ignore issues.

3. Final Answer:

   Provide clear, constructive comments with examples -> Option A

4. Quick Check:

   Constructive feedback = clear + helpful [OK]

Hint: Be clear and helpful in feedback [OK]

Common Mistakes:

• Giving vague or rude comments
• Ignoring minor but important issues
• Only pointing out syntax errors

3. During a code review, you see this Python snippet:

def add_numbers(a, b):
    return a + b

result = add_numbers(2, '3')
print(result)

What will happen when this code runs?

medium

A. It will print 5

B. It will print 23

C. It will raise a TypeError

D. It will print null

Solution

1. Step 1: Analyze function call with mixed types

   The function adds an integer 2 and a string '3', which is invalid in Python.

2. Step 2: Understand Python behavior on adding int and str

   Python raises a TypeError when trying to add int and str directly.

3. Final Answer:

   It will raise a TypeError -> Option C

4. Quick Check:

   int + str = TypeError [OK]

Hint: Adding int and string causes TypeError in Python [OK]

Common Mistakes:

• Assuming Python converts string to int automatically
• Thinking it concatenates as strings
• Expecting numeric addition without error

4. You find this JavaScript code during review:

function multiply(x, y) {
  return x * y;
}

console.log(multiply(5));

What is the issue and how to fix it?

medium

A. multiply is missing one argument; fix by passing two arguments

B. multiply returns NaN; fix by setting default value for y

C. No issue; it prints 5

D. multiply throws error; fix by wrapping in try-catch

Solution

1. Step 1: Check function call with missing argument

   Calling multiply(5) passes only one argument; y is undefined.

2. Step 2: Understand JavaScript behavior multiplying number and undefined

   Multiplying number by undefined results in NaN (Not a Number).

3. Step 3: Fix by setting default value for y

   Use default parameter like function multiply(x, y = 1) to avoid NaN.

4. Final Answer:

   multiply returns NaN; fix by setting default value for y -> Option B

5. Quick Check:

   Missing arg causes NaN; default fixes [OK]

Hint: Missing JS args can cause NaN; use defaults [OK]

Common Mistakes:

• Assuming missing argument is zero
• Expecting error instead of NaN
• Ignoring default parameter usage

5. You review this Python code snippet:

data = [1, 2, 3, 4, 5]
result = {x: x*2 for x in data if x > 2}
result[3] = 10
print(result)

What is the final output and what does it teach about code review?

hard

A. {3: 6, 4: 8, 5: 10} - Code review helps spot logic and mutation issues

B. {1: 2, 2: 4, 3: 6, 4: 8, 5: 10} - Code review ensures all data processed

C. Error - Code review prevents runtime exceptions

D. {3: 10, 4: 8, 5: 10} - Code review helps catch unintended data changes

Solution

1. Step 1: Understand dictionary comprehension with condition

   Creates dict with keys 3,4,5 and values doubled: {3:6,4:8,5:10}.

2. Step 2: Note mutation of result[3]

   Code changes key 3's value from 6 to 10 explicitly.

3. Step 3: Final output and lesson

   Prints {3:10,4:8,5:10}. Code review helps catch such unintended mutations.

4. Final Answer:

   {3: 10, 4: 8, 5: 10} - Code review helps catch unintended data changes -> Option D

5. Quick Check:

   Mutation changes dict; review catches it [OK]

Hint: Check data changes carefully during review [OK]

Common Mistakes:

• Ignoring dictionary mutation after comprehension
• Assuming all data keys included
• Expecting error instead of changed output