Verification times (times, never, atLeast) in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to verify that the method process() was called exactly once.

JUnit

verify(mockObject, [1]).process();

Drag options to blanks, or click blank then click option'

AatLeast(1)

Bnever()

Ctimes(1)

Dtimes(0)

Attempts:

3 left

💡 Hint

Common Mistakes

Using never() will check that the method was never called.

Using atLeast(1) allows one or more calls, not exactly one.

Using times(1) verifies that the method was called exactly once.

2fill in blank

medium

Complete the code to verify that the method save() was never called.

JUnit

verify(mockObject, [1]).save();

Drag options to blanks, or click blank then click option'

Anever()

Btimes(1)

CatLeast(1)

Dtimes(0)

Attempts:

3 left

💡 Hint

Common Mistakes

Using times(0) is similar but never() is clearer.

Using atLeast(1) would allow calls, which is incorrect here.

Using never() verifies that the method was not called at all.

3fill in blank

hard

Fix the error in the verification to check that update() was called at least twice.

JUnit

verify(mockObject, [1]).update();

Drag options to blanks, or click blank then click option'

Atimes(2)

Bnever()

Ctimes(1)

DatLeast(2)

Attempts:

3 left

💡 Hint

Common Mistakes

Using times(2) checks for exactly two calls, not at least two.

Using never() means no calls, which is wrong here.

Using atLeast(2) verifies that the method was called two or more times.

4fill in blank

hard

Fill both blanks to verify that delete() was called exactly three times and create() was never called.

JUnit

verify(mockObject, [1]).delete();
verify(mockObject, [2]).create();

Drag options to blanks, or click blank then click option'

Atimes(3)

Bnever()

CatLeast(1)

Dtimes(1)

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up never() and times(0).

Using atLeast(1) instead of times(3) for exact calls.

Use times(3) to check exactly three calls and never() to check zero calls.

5fill in blank

hard

Fill all three blanks to verify that start() was called at least once, stop() was called exactly twice, and reset() was never called.

JUnit

verify(mockObject, [1]).start();
verify(mockObject, [2]).stop();
verify(mockObject, [3]).reset();

Drag options to blanks, or click blank then click option'

AatLeast(1)

Btimes(2)

Cnever()

Dtimes(1)

Attempts:

3 left

💡 Hint

Common Mistakes

Using times(1) instead of atLeast(1) for the start() method.

Confusing never() with times(0).

Use atLeast(1) for one or more calls, times(2) for exactly two calls, and never() for zero calls.

Practice

1. Which Mockito verification method checks that a method was called exactly 3 times?

easy

A. verify(mock, atMost(3)).method()

B. verify(mock, never()).method()

C. verify(mock, atLeast(3)).method()

D. verify(mock, times(3)).method()

Solution

1. Step 1: Understand times(n) usage

   The times(n) method verifies that the method was called exactly n times.

2. Step 2: Match the exact call count

   Since the question asks for exactly 3 calls, times(3) is the correct choice.

3. Final Answer:

   verify(mock, times(3)).method() -> Option D

4. Quick Check:

   Exact call count = times(n) [OK]

Hint: Use times(n) for exact call count verification [OK]

Common Mistakes:

• Confusing times(n) with atLeast(n)
• Using never() when calls exist
• Using atMost(n) instead of times(n)

2. Which of the following is the correct syntax to verify that a method was never called using Mockito?

easy

A. verify(mock, never()).method();

B. verify(mock, atLeast(0)).method();

C. verify(mock, times(0));

D. verify(mock).never().method();

Solution

1. Step 1: Identify the correct method for zero calls

   Mockito provides never() to verify that a method was not called at all.

2. Step 2: Check syntax correctness

   The correct syntax is verify(mock, never()).method();. Using times(0) also works but never() is clearer and preferred.

3. Final Answer:

   verify(mock, never()).method(); -> Option A

4. Quick Check:

   No calls = never() [OK]

Hint: Use never() to verify zero calls clearly [OK]

Common Mistakes:

• Using times(0) instead of never() for clarity
• Incorrect chaining like verify(mock).never()
• Using atLeast(0) which always passes

3. Given the following code snippet:

verify(mock, atLeast(2)).process();

Which statement is true about the verification?

medium

A. The method process() must be called exactly 2 times.

B. The method process() must be called at most 2 times.

C. The method process() must be called at least 2 times or more.

D. The method process() must never be called.

Solution

1. Step 1: Understand atLeast(n) meaning

   The atLeast(n) method verifies that the method was called at least n times, meaning 2 or more times.

2. Step 2: Match the verification condition

   Since the code uses atLeast(2), it means the method must be called 2 or more times, not exactly 2.

3. Final Answer:

   The method process() must be called at least 2 times or more. -> Option C

4. Quick Check:

   Minimum calls = atLeast(n) [OK]

Hint: atLeast(n) means minimum n calls, not exact [OK]

Common Mistakes:

• Confusing atLeast(n) with times(n)
• Thinking atLeast(n) means at most n
• Assuming never() means zero calls only

4. Identify the error in this Mockito verification:

verify(mock, never).execute();

medium

A. Using times() instead of never()

B. Missing parentheses after never()

C. Incorrect method name execute()

D. No error, syntax is correct

Solution

1. Step 1: Check syntax of never()

   The never() method requires parentheses to be called as a method.

2. Step 2: Identify missing parentheses

   The code uses never without parentheses, which is a syntax error.

3. Final Answer:

   Missing parentheses after never() -> Option B

4. Quick Check:

   never() requires parentheses [OK]

Hint: Always add () after never to avoid syntax errors [OK]

Common Mistakes:

• Omitting parentheses after never
• Confusing never with times(0)
• Assuming method name causes error

5. You want to verify that a method update() was called at least once but no more than 5 times. Which Mockito verification code correctly expresses this?

hard

A. verify(mock, atLeast(1)).update(); verify(mock, atMost(5)).update();

B. verify(mock, times(1)).update(); verify(mock, times(5)).update();

C. verify(mock, never()).update();

D. verify(mock, atLeast(5)).update();

Solution

1. Step 1: Understand the requirement

   The method update() must be called at least once and at most 5 times.

2. Step 2: Use correct verification methods

   Use atLeast(1) to check minimum calls and atMost(5) to check maximum calls.

3. Step 3: Combine verifications

   Both verifications must be done separately to ensure the call count is between 1 and 5.

4. Final Answer:

   verify(mock, atLeast(1)).update(); verify(mock, atMost(5)).update(); -> Option A

5. Quick Check:

   Range check = atLeast + atMost [OK]

Hint: Combine atLeast(n) and atMost(m) for call count range [OK]

Common Mistakes:

• Using times() twice with different values
• Using never() when calls exist
• Using only atLeast(5) which ignores max limit