@CsvSource for inline CSV data in JUnit - Build an Automation Script

Test addition method with multiple inputs using @CsvSource

Preconditions (2)

Step 1: Create a parameterized test method annotated with @ParameterizedTest

Step 2: Use @CsvSource to provide inline CSV data with pairs of integers and their expected sum

Step 3: For each CSV row, call add(a, b) with the first two values

Step 4: Assert that the result equals the expected sum (third value)

✅ Expected Result: The test passes for all CSV input rows verifying the add method returns correct sums

Automation Requirements - JUnit 5

Assertions Needed:

Assert that add(a, b) equals expected sum for each CSV input row

Best Practices:

Use @ParameterizedTest with @CsvSource for inline data

Use descriptive test method names

Use assertions from org.junit.jupiter.api.Assertions

Keep test method simple and focused

Automated Solution

JUnit

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.CsvSource;
import static org.junit.jupiter.api.Assertions.assertEquals;

public class CalculatorTest {

    // Method to test
    public int add(int a, int b) {
        return a + b;
    }

    @ParameterizedTest(name = "add({0}, {1}) = {2}")
    @CsvSource({
        "1, 2, 3",
        "5, 7, 12",
        "10, 15, 25",
        "0, 0, 0",
        "-1, 1, 0"
    })
    void testAdd(int a, int b, int expectedSum) {
        assertEquals(expectedSum, add(a, b));
    }
}

This test class CalculatorTest contains a simple add method to add two integers.

The test method testAdd is annotated with @ParameterizedTest and @CsvSource to provide multiple sets of input data inline as CSV strings.

Each CSV row has three values: the first two are inputs a and b, and the third is the expected sum.

The test runs once for each CSV row, calling add(a, b) and asserting the result equals expectedSum.

This approach keeps the test concise, readable, and easy to add more test cases by just adding more CSV lines.

Common Mistakes - 4 Pitfalls

Using @CsvFileSource instead of @CsvSource for inline data

Not matching the number of parameters in the test method to CSV columns

Using string parameters without converting to int for numeric tests

Hardcoding expected results inside the test method instead of using CSV

Bonus Challenge

Now add data-driven testing with 3 different inputs including negative numbers and zero

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