@ParameterizedTest
- Java course
- Advanced
- Lesson 46/82
- 5 min
Learn parameterized tests with @ParameterizedTest.
@ParameterizedTest
To run the same test with different inputs, use @ParameterizedTest. With @ValueSource you provide a simple array of values; the test runs once for each value.
@ParameterizedTest
@ValueSource(ints = {1, 2, 3})
void testPositive(int number) {
assertTrue(number > 0);
}This is cleaner than copying and pasting the same test. Each input is reported as a separate test; if one fails, the others still run. Types like ints, strings, doubles can be used.
Multiple inputs with @CsvSource
When multiple arguments are needed, use @CsvSource. Each row contains comma-separated values; they are passed to the test method as parameters.
@ParameterizedTest
@CsvSource({"2, 3, 5", "4, 4, 8"})
void testAdd(int a, int b, int expected) {
assertEquals(expected, a + b);
}This provides table-like test data. Each row is a separate scenario and produces its own result. For complex scenarios, @MethodSource with a factory method that returns a Stream can also be used.
Practice Write a parameterized positive number test
Define a NumberTest class. Write a @ParameterizedTest method testPositive with @ValueSource(ints = {1, 2, 3, 4}); the parameter is int number and the method calls assertTrue(number > 0). Add a main method that loops over 1, 2, 3, checks the same positive condition and prints how many are positive with System.out.println.
Starter code
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.ValueSource;
import static org.junit.jupiter.api.Assertions.*;
// Define the NumberTest class
// Write testPositive with the parameterized test annotation and value source annotation
// Add a main method that prints the count of positive numbersSample solution
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.ValueSource;
import static org.junit.jupiter.api.Assertions.*;
class NumberTest {
@ParameterizedTest
@ValueSource(ints = {1, 2, 3, 4})
void testPositive(int number) {
assertTrue(number > 0);
}
public static void main(String[] args) {
int count = 0;
for (int n : new int[]{1, 2, 3}) {
if (n > 0) count++;
}
System.out.println(count);
}
}Expected output
3
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which annotation is used together with @ParameterizedTest?
- @Test
- @ValueSource Correct answer
- @BeforeEach
- @DisplayName
Explanation: @ValueSource provides the input values.
2 Match source annotations
| Term | Meaning |
|---|---|
@ValueSource |
Single-type simple array |
@CsvSource |
Comma-separated rows |
@MethodSource |
Stream factory method |
@EnumSource |
Enum values |
3 Complete the ValueSource call
@ParameterizedTest
@____(strings = {"a", "b"})
void testLetter(String s) {
assertNotNull(s);
}@ParameterizedTest
@ValueSource(strings = {"a", "b"})
void testLetter(String s) {
assertNotNull(s);
}Explanation: @ValueSource provides a simple array of values.