Parameterized Unit Tests with JUnit 5

Overview

Provides patterns for parameterized unit tests in Java using JUnit 5. Covers

@ValueSource

,

@CsvSource

,

@MethodSource

,

@EnumSource

,

@ArgumentsSource

, and custom display names. Reduces test duplication by running the same test logic with multiple input values.

When to Use

• Writing JUnit tests with multiple input combinations
• Implementing data-driven tests in Java
• Running same test with different values (boundary analysis)
• Testing multiple scenarios from single test method

Instructions

1. Add dependency: Ensure

   junit-jupiter-params

   is on test classpath (included in

   junit-jupiter

   )
2. Choose source:

   @ValueSource

   for simple values,

   @CsvSource

   for tabular data,

   @MethodSource

   for complex objects
3. Match parameters: Test method parameters must match data source types
4. Set display names: Use

   name = "{0}..."

   for readable output
5. Validate: Run

   ./gradlew test --info

   or

   mvn test

   and verify all parameter combinations execute

Examples

Maven / Gradle Dependency

JUnit 5 parameterized tests require

junit-jupiter

(includes params). Add

assertj-core

for assertions:

<!-- Maven -->
<dependency>
  <groupId>org.junit.jupiter</groupId>
  <artifactId>junit-jupiter</artifactId>
  <scope>test</scope>
</dependency>

// Gradle
testImplementation("org.junit.jupiter:junit-jupiter")

@ValueSource

— Simple Values

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.ValueSource;
import static org.assertj.core.api.Assertions.*;

@ParameterizedTest
@ValueSource(strings = {"hello", "world", "test"})
void shouldCapitalizeAllStrings(String input) {
  assertThat(StringUtils.capitalize(input)).isNotEmpty();
}

@ParameterizedTest
@ValueSource(ints = {1, 2, 3, 4, 5})
void shouldBePositive(int number) {
  assertThat(number).isPositive();
}

@ParameterizedTest
@ValueSource(ints = {Integer.MIN_VALUE, -1, 0, 1, Integer.MAX_VALUE})
void shouldHandleBoundaryValues(int value) {
  assertThat(Math.incrementExact(value)).isGreaterThan(value);
}

@CsvSource

— Tabular Data

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.CsvSource;

@ParameterizedTest
@CsvSource({
  "alice@example.com, true",
  "bob@gmail.com,     true",
  "invalid-email,     false",
  "user@,             false",
  "@example.com,       false"
})
void shouldValidateEmailAddresses(String email, boolean expected) {
  assertThat(UserValidator.isValidEmail(email)).isEqualTo(expected);
}

@MethodSource

— Complex Data

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.MethodSource;
import java.util.stream.Stream;

@ParameterizedTest
@MethodSource("additionTestCases")
void shouldAddNumbersCorrectly(int a, int b, int expected) {
  assertThat(Calculator.add(a, b)).isEqualTo(expected);
}

static Stream<Arguments> additionTestCases() {
  return Stream.of(
    Arguments.of(1, 2, 3),
    Arguments.of(0, 0, 0),
    Arguments.of(-1, 1, 0),
    Arguments.of(100, 200, 300)
  );
}

@EnumSource

— Enum Values

@ParameterizedTest
@EnumSource(Status.class)
void shouldHandleAllStatuses(Status status) {
  assertThat(status).isNotNull();
}

@ParameterizedTest
@EnumSource(value = Status.class, names = {"ACTIVE", "INACTIVE"})
void shouldHandleSpecificStatuses(Status status) {
  assertThat(status).isIn(Status.ACTIVE, Status.INACTIVE);
}

Custom Display Names

@ParameterizedTest(name = "Discount of {0}% should be calculated correctly")
@ValueSource(ints = {5, 10, 15, 20})
void shouldApplyDiscount(int discountPercent) {
  double result = DiscountCalculator.apply(100.0, discountPercent);
  assertThat(result).isEqualTo(100.0 * (1 - discountPercent / 100.0));
}

Custom

ArgumentsProvider

class RangeValidatorProvider implements ArgumentsProvider {
  @Override
  public Stream<? extends Arguments> provideArguments(ExtensionContext context) {
    return Stream.of(
      Arguments.of(0, 0, 100, true),
      Arguments.of(50, 0, 100, true),
      Arguments.of(-1, 0, 100, false),
      Arguments.of(101, 0, 100, false)
    );
  }
}

@ParameterizedTest
@ArgumentsSource(RangeValidatorProvider.class)
void shouldValidateRange(int value, int min, int max, boolean expected) {
  assertThat(RangeValidator.isInRange(value, min, max)).isEqualTo(expected);
}

Error Condition Testing

@ParameterizedTest
@ValueSource(strings = {"", " ", null})
void shouldThrowExceptionForInvalidInput(String input) {
  assertThatThrownBy(() -> Parser.parse(input))
    .isInstanceOf(IllegalArgumentException.class);
}

Best Practices

• Use descriptive display names:

  name = "{0}..."

  for readable output
• Test boundary values: include min, max, zero, and edge cases
• Keep test logic focused: single assertion per parameter set
• Use

  @MethodSource

  for complex objects,

  @CsvSource

  for tabular data
• Organize test data logically — group related scenarios together

Constraints and Warnings

• Parameter count must match: Number of parameters from source must match test method signature

• @ValueSource

  limitation: Only supports primitives, strings, and enums — not objects or null directly
• CSV escaping: Strings with commas must use single quotes in

  @CsvSource

• @MethodSource

  visibility: Factory methods must be static in the same test class
• Display name placeholders: Use

  {0}

  ,

  {1}

  , etc. to reference parameters
• Execution count: Each parameter set runs as a separate test invocation

References

• JUnit 5 Parameterized Tests

• @ParameterizedTest

  API