Testing failsafe scenarios in Drone Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output when GPS signal is lost?

Consider this drone control snippet that triggers a failsafe when GPS signal is lost. What will be printed?

Drone Programming

def check_gps(signal_strength):
    if signal_strength < 20:
        print("Failsafe activated: Returning to home.")
    else:
        print("GPS signal stable.")

check_gps(15)

A Failsafe activated: Returning to home.

B GPS signal stable.

C Error: signal_strength undefined

D Failsafe activated: Landing immediately.

💡 Hint

Check the condition for signal strength less than 20.

The function prints the failsafe message when signal_strength is below 20. Since 15 < 20, it prints the failsafe message.

❓ Predict Output

intermediate

What happens if battery level is exactly at threshold?

This code triggers a failsafe if battery is below 15%. What will it print if battery is exactly 15%?

Drone Programming

def battery_check(level):
    if level < 15:
        print("Failsafe: Land immediately.")
    else:
        print("Battery level sufficient.")

battery_check(15)

A No output

B Failsafe: Land immediately.

C Battery level sufficient.

D Failsafe: Return to home.

💡 Hint

Check if the condition includes equality or only less than.

The condition is level < 15, so 15 is not less than 15. It prints the else branch.

❓ Predict Output

advanced

What error occurs if failsafe function is called without parameters?

What error will this code raise when calling failsafe() without arguments?

Drone Programming

def failsafe(mode):
    if mode == "return":
        print("Returning to home.")
    elif mode == "land":
        print("Landing immediately.")
    else:
        print("Unknown mode.")

failsafe()

A TypeError: failsafe() missing 1 required positional argument: 'mode'

B NameError: mode is not defined

C No output

D SyntaxError

💡 Hint

Check the function definition and how it is called.

The function requires one argument 'mode'. Calling it without arguments raises a TypeError.

🧠 Conceptual

advanced

Which condition triggers failsafe on sensor failure?

Given a sensor reading variable 'sensor_ok' that is True when sensors work and False when they fail, which condition correctly triggers the failsafe?

A

if sensor_ok = False:
    activate_failsafe()

B

if sensor_ok == False:
    activate_failsafe()

C

if sensor_ok != True:
    activate_failsafe()

D

if sensor_ok == True:
    activate_failsafe()

💡 Hint

Remember the difference between assignment and comparison.

Option B correctly compares sensor_ok to False using '=='. Option B uses assignment '=' which performs an assignment instead of a comparison. Option B also works logically but is less clear. Option B triggers failsafe when sensor is OK, which is wrong.

❓ Predict Output

expert

What is the output of the failsafe retry loop?

This code tries to reconnect up to 3 times. What will it print?

Drone Programming

def reconnect():
    for attempt in range(1, 4):
        print(f"Attempt {attempt}: Trying to reconnect...")
        if attempt == 2:
            print("Reconnected successfully.")
            break
    else:
        print("Failed to reconnect after 3 attempts.")

reconnect()

A

Attempt 1: Trying to reconnect...
Failed to reconnect after 3 attempts.

B

Attempt 1: Trying to reconnect...
Attempt 2: Trying to reconnect...
Attempt 3: Trying to reconnect...
Failed to reconnect after 3 attempts.

C Reconnected successfully.

D

Attempt 1: Trying to reconnect...
Attempt 2: Trying to reconnect...
Reconnected successfully.

💡 Hint

Check how the break affects the else clause of the loop.

The loop breaks on attempt 2 after printing success, so the else clause does not run.

Practice

1. What is the main purpose of testing failsafe scenarios in drone programming?

easy

A. To add more features to the drone's camera

B. To improve the drone's speed and flight time

C. To ensure the drone handles problems safely and avoids crashes

D. To make the drone fly higher than usual

Solution

1. Step 1: Understand failsafe scenarios

   Failsafe scenarios are tests to check how the drone reacts to problems like lost connection or low battery.

2. Step 2: Identify the main goal

   The main goal is to keep the drone safe and avoid crashes during these problems.

3. Final Answer:

   To ensure the drone handles problems safely and avoids crashes -> Option C

4. Quick Check:

   Failsafe = safety first [OK]

Hint: Failsafe means safety during problems [OK]

Common Mistakes:

• Confusing failsafe with performance improvements
• Thinking failsafe adds new features
• Assuming failsafe makes drone fly higher

2. Which of the following code snippets correctly simulates a low battery failsafe check in drone programming?

easy

A. if battery_level < 20:
initiate_landing()

B. if battery_level > 20:
initiate_landing()

C. if battery_level == 100:
initiate_landing()

D. if battery_level != 20:
initiate_landing()

Solution

1. Step 1: Understand the battery check condition

   Low battery means battery level is less than a safe threshold, here 20%.

2. Step 2: Match condition to code

   Only 'if battery_level < 20:' correctly checks for low battery to start landing.

3. Final Answer:

   if battery_level < 20: initiate_landing() -> Option A

4. Quick Check:

   Low battery = less than 20% [OK]

Hint: Check if battery is below threshold to trigger landing [OK]

Common Mistakes:

• Using greater than instead of less than
• Checking for exact battery value
• Using not equal instead of less than

3. Given the code below simulating a lost connection failsafe, what will be printed?

connection_status = "lost"
if connection_status == "lost":
    print("Return to home activated")
else:
    print("Continue flying")

medium

A. Return to home activated

B. Continue flying

C. No output

D. SyntaxError

Solution

1. Step 1: Check the value of connection_status

   The variable connection_status is set to "lost".

2. Step 2: Evaluate the if condition

   The condition 'connection_status == "lost"' is true, so the first print runs.

3. Final Answer:

   Return to home activated -> Option A

4. Quick Check:

   Lost connection triggers return home [OK]

Hint: Match variable value to if condition [OK]

Common Mistakes:

• Confusing else output with if output
• Assuming no output if condition true
• Thinking code has syntax error

4. The following code is meant to trigger an emergency landing if the drone loses GPS signal, but it does not work as expected. What is the error?

gps_signal = False
if gps_signal = False:
    emergency_landing()

medium

A. The variable gps_signal is not defined

B. Missing parentheses after emergency_landing

C. gps_signal should be True to trigger landing

D. Using assignment '=' instead of comparison '==' in the if condition

Solution

1. Step 1: Identify the if condition syntax

   The code uses 'if gps_signal = False:', which assigns False instead of comparing.

2. Step 2: Correct the comparison operator

   It should be 'if gps_signal == False:' to check the value properly.

3. Final Answer:

   Using assignment '=' instead of comparison '==' in the if condition -> Option D

4. Quick Check:

   Use '==' for comparison, not '=' [OK]

Hint: Use '==' to compare, '=' to assign [OK]

Common Mistakes:

• Confusing '=' and '==' in conditions
• Forgetting parentheses on function calls
• Assuming variable is undefined

5. You want to test a failsafe scenario where the drone must land immediately if either the battery is below 15% or the GPS signal is lost. Which code correctly implements this logic?

battery_level = 10
gps_signal = False
# Choose the correct condition to trigger landing
if _____:
    emergency_landing()

hard

A. battery_level < 15 and gps_signal == False

B. battery_level < 15 or gps_signal == False

C. battery_level > 15 or gps_signal == True

D. battery_level > 15 and gps_signal == True

Solution

1. Step 1: Understand the condition requirements

   The drone should land if battery is below 15% OR GPS signal is lost (False).

2. Step 2: Match logical operator to condition

   Use 'or' because either condition triggers landing, so 'battery_level < 15 or gps_signal == False'.

3. Final Answer:

   battery_level < 15 or gps_signal == False -> Option B

4. Quick Check:

   Use OR for either condition triggers landing [OK]

Hint: Use OR to combine multiple failsafe triggers [OK]

Common Mistakes:

• Using AND instead of OR
• Checking for battery > 15 instead of < 15
• Confusing GPS signal True/False meaning