@CsvSource for inline CSV data in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to use @CsvSource with two values.

JUnit

@ParameterizedTest
@CsvSource([1])
void testSum(int a, int b) {
    assertEquals(a + b, a + b);
}

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

A"1; 2"

B"1, 2"

C"1|2"

D"1 2"

Attempts:

3 left

💡 Hint

Common Mistakes

Using semicolons or other separators instead of commas.

Not putting the CSV line inside quotes.

The @CsvSource expects comma-separated values inside quotes for each line.

2fill in blank

medium

Complete the code to add multiple CSV lines in @CsvSource.

JUnit

@ParameterizedTest
@CsvSource([1])
void testMultiply(int a, int b, int expected) {
    assertEquals(expected, a * b);
}

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

A"1 2 2", "3 4 12"

B"1; 2; 2", "3; 4; 12"

C"1|2|2", "3|4|12"

D"1, 2, 2", "3, 4, 12"

Attempts:

3 left

💡 Hint

Common Mistakes

Using semicolons or pipes instead of commas inside lines.

Not separating lines with commas.

Multiple CSV lines are separated by commas and each line is a quoted string with comma-separated values.

3fill in blank

hard

Fix the error in the @CsvSource annotation to correctly pass three test cases.

JUnit

@ParameterizedTest
@CsvSource([1])
void testConcat(String a, String b, String expected) {
    assertEquals(expected, a + b);
}

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

A"Hello|World|HelloWorld", "Java|Test|JavaTest", "JUnit|5|JUnit5"

B"Hello; World; HelloWorld", "Java; Test; JavaTest", "JUnit; 5; JUnit5"

C"Hello, World, HelloWorld", "Java, Test, JavaTest", "JUnit, 5, JUnit5"

D"Hello World HelloWorld", "Java Test JavaTest", "JUnit 5 JUnit5"

Attempts:

3 left

💡 Hint

Common Mistakes

Using semicolons or pipes instead of commas inside the CSV lines.

Not separating lines with commas.

The correct CSV format uses commas inside quotes to separate values and commas between lines.

4fill in blank

hard

Fill both blanks to correctly use @CsvSource with mixed data types.

JUnit

@ParameterizedTest
@CsvSource([1])
void testMixedTypes(int id, String name, boolean active) {
    assertTrue(active);
    assertNotNull(name);
    assertTrue(id > 0);
}

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

A"1, Alice, true", "2, Bob, true"

B"1, Alice, true", "2, Bob, false"

C"1; Alice; true", "2; Bob; false"

D"1|Alice|true", "2|Bob|true"

Attempts:

3 left

💡 Hint

Common Mistakes

Using semicolons or pipes instead of commas.

Including false where the test expects true.

Each CSV line must be a quoted string with comma-separated values. The test expects 'active' to be true, so lines with false would fail.

5fill in blank

hard

Fill all three blanks to create a @CsvSource with three test cases and correct syntax.

JUnit

@ParameterizedTest
@CsvSource([1])
void testDivide(int numerator, int denominator, int expected) {
    assertEquals(expected, numerator / denominator);
}

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

A"10, 2, 5"

B"20, 4, 5"

C"30, 5, 6"

D"10; 2; 5"

Attempts:

3 left

💡 Hint

Common Mistakes

Using semicolons inside the CSV lines.

Not separating lines with commas.

Each CSV line is a quoted string with comma-separated values. Lines are separated by commas outside the quotes.

Practice

1.

What is the main purpose of using @CsvSource in JUnit tests?

easy

A. To run the same test multiple times with different input data

B. To connect to a database and fetch test data

C. To generate random test data automatically

D. To create a graphical user interface for tests

Solution

1. Step 1: Understand the role of @CsvSource

   @CsvSource allows specifying multiple sets of input data inline for a single test method.

2. Step 2: Identify the purpose in testing

   This lets the test run repeatedly with each data set, checking behavior for different inputs.

3. Final Answer:

   To run the same test multiple times with different input data -> Option A

4. Quick Check:

   @CsvSource runs tests with multiple inputs [OK]

Hint: Remember: @CsvSource repeats tests with different data [OK]

Common Mistakes:

• Thinking @CsvSource connects to databases
• Confusing it with random data generation
• Assuming it creates UI elements

2.

Which of the following is the correct syntax to use @CsvSource for a test method with two parameters int a and int b?

@ParameterizedTest
@CsvSource({"1, 2", "3, 4"})
void testSum(int a, int b) { ... }

easy

A. @CsvSource({"1; 2", "3; 4"})

B. @CsvSource({"1, 2", "3, 4"})

C. @CsvSource({"1 2", "3 4"})

D. @CsvSource({"1|2", "3|4"})

Solution

1. Step 1: Check the delimiter used in @CsvSource

   The default delimiter for @CsvSource is a comma (,), so values should be separated by commas.

2. Step 2: Match the syntax with parameters

   Since the method expects two int parameters, each CSV line must have two comma-separated values.

3. Final Answer:

   @CsvSource({"1, 2", "3, 4"}) -> Option B

4. Quick Check:

   Comma separates values in @CsvSource [OK]

Hint: Use commas to separate values inside @CsvSource strings [OK]

Common Mistakes:

• Using semicolons or spaces instead of commas
• Using wrong delimiters like |
• Not matching parameter count with CSV values

3.

What will be the output of the following JUnit test when run with @CsvSource?

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

medium

A. All tests fail

B. All tests pass

C. The first test fails

D. The last test fails

Solution

1. Step 1: Evaluate each test case

   Test 1: 2 + 3 = 5 matches expected 5 (pass) Test 2: 4 + 5 = 9 matches expected 9 (pass) Test 3: 1 + 1 = 2 does not match expected 3 (fail)

2. Step 2: Determine overall result

   Since one test fails, the test suite reports failure for that case.

3. Final Answer:

   The last test fails -> Option D

4. Quick Check:

   Check sums against expected values [OK]

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

Common Mistakes:

• Assuming all tests pass without checking expected values
• Ignoring the last test case
• Confusing parameter order

4.

Identify the error in this JUnit test using @CsvSource:

@ParameterizedTest
@CsvSource({"apple, 1", "banana"})
void testFruitCount(String fruit, int count) {
    assertTrue(count > 0);
}

medium

A. assertTrue is used incorrectly

B. Method parameters do not match test data types

C. Missing second value in second CSV line causes error

D. @CsvSource cannot have more than one line

Solution

1. Step 1: Check CSV lines against method parameters

   The method expects two parameters: a String and an int. The first CSV line has two values, but the second line has only one.

2. Step 2: Understand the impact of missing value

   Missing the second value in the second line causes a runtime error because the test cannot map parameters properly.

3. Final Answer:

   Missing second value in second CSV line causes error -> Option C

4. Quick Check:

   Each CSV line must have values matching parameters [OK]

Hint: Count CSV values to match method parameters exactly [OK]

Common Mistakes:

• Ignoring missing values in CSV lines
• Assuming assertTrue usage causes error
• Thinking @CsvSource limits lines to one

5.

You want to test a method isAdult(int age) that returns true if age is 18 or more, false otherwise. Which @CsvSource usage correctly tests ages 17, 18, and 20 with expected results?

hard

A. @CsvSource({"17, false", "18, true", "20, true"})

B. @CsvSource({"17; false", "18; true", "20; true"})

C. @CsvSource({"17 true", "18 true", "20 true"})

D. @CsvSource({"17|false", "18|true", "20|true"})

Solution

1. Step 1: Use correct delimiter for @CsvSource

   The default delimiter is a comma, so values must be comma-separated.

2. Step 2: Match test data with method parameters

   Each line has an int age and a boolean expected result, correctly formatted with commas.

3. Final Answer:

   @CsvSource({"17, false", "18, true", "20, true"}) -> Option A

4. Quick Check:

   Comma-separated values match parameters and expected results [OK]

Hint: Use commas to separate all values in @CsvSource [OK]

Common Mistakes:

• Using semicolons or spaces instead of commas
• Using wrong delimiters like |
• Not matching parameter count or types