Argument matchers (any, eq) in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to verify a method call with any String argument.

JUnit

verify(mockObject).someMethod([1]());

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

AanyString

Beq

CanyInt

DisNull

Attempts:

3 left

💡 Hint

Common Mistakes

Using eq without specifying the exact argument.

Using anyInt() which matches integers, not strings.

The anyString() matcher matches any String argument in the method call verification.

2fill in blank

medium

Complete the code to verify a method call with an exact argument "test".

JUnit

verify(mockObject).someMethod([1]("test"));

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

Aany

BanyString

Ceq

DisNull

Attempts:

3 left

💡 Hint

Common Mistakes

Using anyString() which matches any string, not the exact one.

Using any() without specifying the type.

The eq("test") matcher verifies the method was called with the exact argument "test".

3fill in blank

hard

Fix the error in the verification by choosing the correct matcher for any Integer argument.

JUnit

verify(mockObject).someMethod([1]());

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

Aeq

BanyInt

CanyString

DanyDouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using anyString() which matches strings, not integers.

Using eq() without specifying the exact integer.

The anyInt() matcher correctly matches any Integer argument in the method call.

4fill in blank

hard

Fill both blanks to verify a method called with exact String "hello" and any Integer argument.

JUnit

verify(mockObject).someMethod([1]("hello"), [2]());

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

Aeq

BanyInt

CanyString

DisNull

Attempts:

3 left

💡 Hint

Common Mistakes

Using anyString() for the first argument instead of eq().

Using eq() for the second argument without specifying a value.

Use eq("hello") to match the exact String and anyInt() to match any Integer argument.

5fill in blank

hard

Fill all three blanks to verify a method called with any String, exact Integer 5, and any Boolean argument.

JUnit

verify(mockObject).someMethod([1](), [2](5), [3]());

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

AanyString

Beq

CanyBoolean

DanyInt

Attempts:

3 left

💡 Hint

Common Mistakes

Using anyInt() instead of eq(5) for the exact integer.

Using eq() without argument for the Boolean.

Use anyString() for any String, eq(5) for exact Integer 5, and anyBoolean() for any Boolean argument.

Practice

1. What does the any() argument matcher do in JUnit Mockito tests?

easy

A. It matches any value of the specified type.

B. It matches only null values.

C. It matches only exact values.

D. It matches values that are greater than zero.

Solution

1. Step 1: Understand the purpose of any()

   The any() matcher is used to accept any argument of a given type in method verification or stubbing.

2. Step 2: Compare with other matchers

   Unlike eq(), which matches exact values, any() is flexible and matches all values of the specified type.

3. Final Answer:

   It matches any value of the specified type. -> Option A

4. Quick Check:

   any() = matches any value [OK]

Hint: Remember: any() accepts all values of a type [OK]

Common Mistakes:

• Confusing any() with eq()
• Thinking any() matches only null
• Assuming any() matches only specific values

2. Which of the following is the correct syntax to verify a method call with an exact argument value using an argument matcher in Mockito?

easy

A. verify(mock).method(any(String.class));

B. verify(mock).method(any());

C. verify(mock).method(eq("test"));

D. verify(mock).method("test");

Solution

1. Step 1: Identify correct use of eq()

   The eq() matcher is used to match an exact argument value in Mockito verification.

2. Step 2: Check syntax correctness

   verify(mock).method(eq("test")); correctly uses eq("test") to verify the method was called with the exact string "test".

3. Final Answer:

   verify(mock).method(eq("test")); -> Option C

4. Quick Check:

   Exact value match = eq() [OK]

Hint: Use eq() to match exact argument values [OK]

Common Mistakes:

• Using any() when exact match is needed
• Omitting eq() for exact value
• Using any() without specifying type

3. Consider the following code snippet:

when(service.process(any(String.class))).thenReturn("done");
String result = service.process("input");

What will be the value of result after execution?

medium

A. "input"

B. null

C. Throws an exception

D. "done"

Solution

1. Step 1: Analyze the stubbing with any()

   The when clause uses any(String.class) to match any string argument and returns "done".

2. Step 2: Check the method call argument

   The method is called with "input", which matches any(String.class), so the stub returns "done".

3. Final Answer:

   "done" -> Option D

4. Quick Check:

   any(String.class) matches "input" = returns "done" [OK]

Hint: any() matches all inputs, so stub returns specified value [OK]

Common Mistakes:

• Assuming method returns input argument
• Thinking any() causes exception
• Ignoring stubbing behavior

4. Identify the error in the following Mockito verification code:

verify(mock).update(eq("data"), any());

medium

A. eq() cannot be used with any().

B. Missing type parameter in any() matcher.

C. verify() should not be used with matchers.

D. No error; code is correct.

Solution

1. Step 1: Check usage of any()

   The any() matcher requires a type parameter like any(String.class) to specify the argument type.

2. Step 2: Confirm correct matcher usage

   Without the type, Mockito cannot determine the argument type, causing a compilation error.

3. Final Answer:

   Missing type parameter in any() matcher. -> Option B

4. Quick Check:

   any() needs type like any(String.class) [OK]

Hint: Always specify type in any() like any(String.class) [OK]

Common Mistakes:

• Using any() without type parameter
• Mixing eq() and any() incorrectly
• Assuming verify() disallows matchers

5. You want to verify a method call that takes two arguments: a String and an Integer. The first argument must be exactly "test", and the second can be any Integer. Which Mockito verification is correct?

hard

A. verify(mock).method(eq("test"), any(Integer.class));

B. verify(mock).method(any(String.class), eq(1));

C. verify(mock).method(any(), any());

D. verify(mock).method(eq("test"), eq(1));

Solution

1. Step 1: Match exact first argument

   The first argument must be exactly "test", so use eq("test").

2. Step 2: Match any Integer second argument

   The second argument can be any Integer, so use any(Integer.class).

3. Step 3: Verify combined usage

   verify(mock).method(eq("test"), any(Integer.class)); correctly combines eq() and any() for the two arguments.

4. Final Answer:

   verify(mock).method(eq("test"), any(Integer.class)); -> Option A

5. Quick Check:

   eq() + any(type) = exact + any argument [OK]

Hint: Use eq() for exact, any(type) for flexible args [OK]

Common Mistakes:

• Swapping argument matchers incorrectly
• Using any() without type
• Using eq() for flexible arguments