Performance metrics (response time, throughput) in Testing Fundamentals - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Response Time

Which of the following best describes response time in performance testing?

A The total time taken to complete all requests in a test.

B The time taken for a system to respond to a single request.

C The number of requests processed per second.

D The amount of data transferred during the test.

💡 Hint

Think about how long a user waits after making a request.

Response time measures how long it takes for the system to reply to one request, not the total or throughput.

❓ Predict Output

intermediate

Calculating Throughput

Given the following test results, what is the throughput (requests per second)?

total_requests = 500
total_time_seconds = 50
throughput = total_requests / total_time_seconds
print(throughput)

Testing Fundamentals

total_requests = 500
total_time_seconds = 50
throughput = total_requests / total_time_seconds
print(throughput)

A 500.0

B 0.1

C 10.0

D 50.0

💡 Hint

Divide total requests by total time in seconds.

Throughput is requests divided by time, so 500 / 50 = 10 requests per second.

❓ assertion

advanced

Validating Response Time Threshold

Which assertion correctly checks that the response time is less than 2 seconds in a test script?

Testing Fundamentals

response_time = 1.8  # seconds

A assert response_time < 2

B assert response_time > 2

C assert response_time == 2

D assert response_time >= 2

💡 Hint

We want to confirm response time is under the limit.

To ensure response time is less than 2 seconds, use < 2 in the assertion.

🔧 Debug

advanced

Identifying Throughput Calculation Error

Find the error in this throughput calculation code snippet:

total_requests = 1000
total_time_seconds = 0
throughput = total_requests / total_time_seconds
print(throughput)

A Throughput will be zero because total_requests is too high.

B No error; throughput will print 1000.

C Syntax error due to missing colon.

D Division by zero error because total_time_seconds is zero.

💡 Hint

Check if dividing by zero is possible.

Dividing by zero causes a runtime error; total_time_seconds cannot be zero.

❓ framework

expert

Choosing the Best Metric for Load Testing

In a load test simulating 1000 users, which metric best indicates how many requests the system handles per second?

A Throughput

B Response time

C Error rate

D CPU usage

💡 Hint

Think about the number of requests processed over time.

Throughput measures requests per second, showing system capacity under load.

Practice

1. What does response time measure in performance testing?

easy

A. The total number of requests per second

B. How fast a single request is completed

C. The amount of data transferred in a request

D. The number of users accessing the system

Solution

1. Step 1: Understand response time meaning

   Response time measures the duration taken to complete one request from start to finish.

2. Step 2: Differentiate from throughput

   Throughput measures how many requests happen over time, not the speed of one request.

3. Final Answer:

   How fast a single request is completed -> Option B

4. Quick Check:

   Response time = speed of one request [OK]

Hint: Response time = speed of one request [OK]

Common Mistakes:

• Confusing response time with throughput
• Thinking response time counts total requests
• Mixing data size with response time

2. Which of the following is the correct unit commonly used to measure throughput?

easy

A. Milliseconds (ms)

B. Bytes

C. Requests per second (RPS)

D. Percentage (%)

Solution

1. Step 1: Identify throughput unit

   Throughput measures how many requests are processed per unit time, commonly requests per second (RPS).

2. Step 2: Exclude other units

   Milliseconds measure time, bytes measure data size, and percentage is not a throughput unit.

3. Final Answer:

   Requests per second (RPS) -> Option C

4. Quick Check:

   Throughput = requests per second [OK]

Hint: Throughput counts requests per second [OK]

Common Mistakes:

• Using time units for throughput
• Confusing data size with throughput
• Selecting percentage as throughput unit

3. Given a system that processes 120 requests in 10 seconds, what is the throughput?

medium

A. 10 requests per second

B. 0.12 requests per second

C. 1200 requests per second

D. 12 requests per second

Solution

1. Step 1: Calculate throughput formula

   Throughput = Total requests / Total time = 120 / 10 seconds.

2. Step 2: Perform division

   120 divided by 10 equals 12 requests per second.

3. Final Answer:

   12 requests per second -> Option D

4. Quick Check:

   120 ÷ 10 = 12 [OK]

Hint: Divide total requests by total time [OK]

Common Mistakes:

• Dividing time by requests instead of requests by time
• Multiplying requests and time
• Confusing throughput with response time

4. A tester recorded the following response times (in ms): 100, 200, 150, 250. The average response time was incorrectly calculated as 700 ms. What is the correct average response time?

medium

A. 175 ms

B. 700 ms

C. 150 ms

D. 200 ms

Solution

1. Step 1: Sum all response times

   Add 100 + 200 + 150 + 250 = 700 ms total.

2. Step 2: Calculate average response time

   Divide total 700 ms by 4 requests = 175 ms average.

3. Final Answer:

   175 ms -> Option A

4. Quick Check:

   700 ÷ 4 = 175 [OK]

Hint: Sum times, then divide by count [OK]

Common Mistakes:

• Using total sum as average
• Dividing by wrong number of requests
• Mixing units in calculation

5. A web server has a throughput of 50 requests per second and an average response time of 200 ms. If the server's throughput doubles but response time remains the same, what happens to the server's capacity and user experience?

hard

A. Capacity doubles; user experience stays consistent

B. Capacity stays same; user experience worsens

C. Capacity doubles; user experience worsens

D. Capacity halves; user experience improves

Solution

1. Step 1: Understand throughput doubling

   Doubling throughput means the server can handle twice as many requests per second, so capacity doubles.

2. Step 2: Analyze response time unchanged

   Since response time stays at 200 ms, the speed per request remains consistent, so user experience does not worsen.

3. Final Answer:

   Capacity doubles; user experience stays consistent -> Option A

4. Quick Check:

   Throughput ↑, response time same = better capacity, same experience [OK]

Hint: More throughput + same response time = better capacity, same experience [OK]

Common Mistakes:

• Assuming response time worsens with throughput increase
• Confusing capacity with response time
• Thinking capacity decreases when throughput increases