Multiple parameter types in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a parameterized test method with two parameters.

JUnit

[1] void testMethod(int number, String text) {}

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

A@Test

B@ParameterizedTest

C@CsvSource

D@ValueSource

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Test instead of @ParameterizedTest for parameterized tests.

Placing the annotation inside the parameter list.

To declare a parameterized test method, use the @ParameterizedTest annotation before the method declaration.

2fill in blank

medium

Complete the code to provide multiple parameters using CSV source.

JUnit

@ParameterizedTest
@CsvSource([1])
void testMethod(int number, String text) {}

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

A"1,apple", "2,banana"

B"1, 'apple', 2, 'banana'"

C"1;apple", "2;banana"

D"1|apple", "2|banana"

Attempts:

3 left

💡 Hint

Common Mistakes

Using semicolons or pipes instead of commas as separators.

Putting all values in one string instead of separate strings.

The @CsvSource annotation expects an array of strings, each string representing a line of CSV values separated by commas. So the correct format is "1,apple", "2,banana".

3fill in blank

hard

Fix the error in the parameterized test method declaration.

JUnit

@ParameterizedTest
@CsvSource({"1,apple", "2,banana"})
void testMethod([1] number, String text) {}

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

Aint

Bdouble

CString

Dboolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using String instead of int for numeric CSV values.

Using incompatible types like boolean or double.

The first parameter corresponds to the first CSV value which is an integer, so the parameter type must be int.

4fill in blank

hard

Fill both blanks to correctly declare a parameterized test with multiple parameter types and source.

JUnit

@ParameterizedTest
@CsvSource([1])
void testMethod([2] number, String text) {}

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

A"3,orange", "4,grape"

Bint

CString

D"3;orange", "4;grape"

Attempts:

3 left

💡 Hint

Common Mistakes

Using semicolons instead of commas in CSV strings.

Using String type for numeric parameters.

The @CsvSource needs strings with comma-separated values, so "3,orange", "4,grape" is correct. The parameter type for number is int.

5fill in blank

hard

Fill all three blanks to complete a parameterized test method with multiple parameter types and CSV source.

JUnit

@ParameterizedTest
@CsvSource([1])
void testMethod([2] number, [3] text) {}

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

A"5,melon", "6,berry"

Bint

CString

Ddouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong separators in CSV strings.

Mixing up parameter types.

The CSV source strings must be comma-separated values. The first parameter is an int matching the first CSV value, and the second parameter is a String matching the second CSV value.

Practice

1. What is the main benefit of using @ParameterizedTest with multiple parameter types in JUnit?

easy

A. It makes tests run faster by skipping assertions.

B. It automatically fixes bugs in the tested code.

C. It allows running the same test method with different input values easily.

D. It generates test reports without writing any code.

Solution

1. Step 1: Understand the purpose of @ParameterizedTest

   @ParameterizedTest lets you run one test method multiple times with different inputs.

2. Step 2: Recognize the benefit of multiple parameter types

   Using multiple parameter types means you can test various input combinations easily, improving coverage.

3. Final Answer:

   It allows running the same test method with different input values easily. -> Option C

4. Quick Check:

   @ParameterizedTest runs tests with many inputs = A [OK]

Hint: Think: same test, many inputs, easy coverage [OK]

Common Mistakes:

• Confusing parameterized tests with automatic bug fixing
• Believing it skips assertions to run faster
• Assuming it generates reports without code

2. Which of the following is the correct syntax to provide multiple parameters of different types using @CsvSource in JUnit?

easy

A. @CsvSource({"1, 'test', true", "2, 'check', false"})

B. @CsvSource(1, 'test', true; 2, 'check', false)

C. @CsvSource([1, 'test', true], [2, 'check', false])

D. @CsvSource("1; 'test'; true", "2; 'check'; false")

Solution

1. Step 1: Recall the correct @CsvSource format

   @CsvSource expects an array of strings, each string with comma-separated values.

2. Step 2: Check each option's syntax

   @CsvSource({"1, 'test', true", "2, 'check', false"}) uses curly braces and comma-separated values inside quotes, which is correct syntax.

3. Final Answer:

   @CsvSource({"1, 'test', true", "2, 'check', false"}) -> Option A

4. Quick Check:

   @CsvSource uses braces and comma-separated strings = C [OK]

Hint: Look for braces and comma-separated quoted strings [OK]

Common Mistakes:

• Using semicolons instead of commas
• Not enclosing the whole list in braces
• Using square brackets instead of braces

3. Given the following JUnit test method, what will be the output when it runs?

@ParameterizedTest
@CsvSource({"2, 3, 5", "4, 5, 9", "1, 1, 3"})
void testSum(int a, int b, int expected) {
    assertEquals(expected, a + b);
}

medium

A. Syntax error prevents tests from running.

B. All tests pass.

C. All tests fail.

D. Two tests pass, one test fails.

Solution

1. Step 1: Check each test case's expected vs actual sum

   Test 1: 2+3=5 matches expected 5 (pass). Test 2: 4+5=9 matches expected 9 (pass). Test 3: 1+1=2 but expected 3 (fail).

2. Step 2: Determine overall test results

   Two tests pass, one test fails due to wrong expected value.

3. Final Answer:

   Two tests pass, one test fails. -> Option D

4. Quick Check:

   Sum matches expected except last = A [OK]

Hint: Add inputs and compare to expected for each case [OK]

Common Mistakes:

• Assuming all pass without checking expected values
• Ignoring the failing test case
• Thinking syntax error occurs due to quotes

4. Identify the error in this JUnit parameterized test using multiple parameter types:

@ParameterizedTest
@CsvSource({"10, 20", "30, 40"})
void testMultiply(int a, int b, int expected) {
    assertEquals(expected, a * b);
}

medium

A. The @CsvSource syntax is incorrect; it should use semicolons instead of commas.

B. The method expects three parameters but only two are provided in @CsvSource.

C. The assertEquals arguments are reversed.

D. The test method should not use @ParameterizedTest with @CsvSource.

Solution

1. Step 1: Compare method parameters with @CsvSource values

   The method expects three parameters (int a, int b, int expected), but each @CsvSource entry has only two values.

2. Step 2: Identify mismatch causing error

   Missing the third parameter in @CsvSource causes a runtime error due to parameter count mismatch.

3. Final Answer:

   The method expects three parameters but only two are provided in @CsvSource. -> Option B

4. Quick Check:

   Parameter count mismatch = B [OK]

Hint: Count parameters in method and CsvSource entries [OK]

Common Mistakes:

• Thinking commas are wrong separators
• Assuming assertEquals argument order causes error
• Believing @ParameterizedTest can't be used with @CsvSource

5. You want to test a method isValidUser(String username, int age, boolean active) using @ParameterizedTest with multiple parameter types. Which @CsvSource entry correctly represents a test case with username "alice", age 30, and active status true?

hard

A. "alice, 30, true"

B. "'alice', 30, true"

C. "alice; 30; true"

D. "alice, '30', 'true'"

Solution

1. Step 1: Understand @CsvSource value format

   Values are comma-separated strings; quotes around strings are optional unless spaces or commas inside.

2. Step 2: Evaluate each option

   "alice, 30, true" correctly uses commas without extra quotes. "'alice', 30, true" adds unnecessary quotes around username. "alice; 30; true" uses semicolons which is invalid. "alice, '30', 'true'" quotes numeric and boolean values unnecessarily.

3. Final Answer:

   "alice, 30, true" -> Option A

4. Quick Check:

   Comma-separated values without extra quotes = D [OK]

Hint: Use commas, quote strings only if needed [OK]

Common Mistakes:

• Using semicolons instead of commas
• Adding quotes around numbers or booleans
• Quoting strings unnecessarily