Junit5: Parameterized tests: Null and Empty Sources

@NullSource, @EmptySource and @NullAndEmptySource annotations are used to supply null and empty values to our parameterized tests.

 

Below table summarizes above annotations.

 

Annotation	Description
@NullSource	Provides a single null argument to the annotated @ParameterizedTest method. It cannot be used for a parameter that has a primitive type.   @NullSource cannot be used for a parameter that has a primitive type.
@EmptySource	provides a single empty argument to the annotated @ParameterizedTest method for parameters of the following types: java.lang.String, java.util.List, java.util.Set, java.util.Map, primitive arrays (ex: int[], char[][], etc.), object arrays (ex: String[], Integer[][], etc.).
@NullAndEmptySource	Composed annotation that combines the functionality of @NullSource and @EmptySource.

 

Example

@ParameterizedTest
@NullAndEmptySource
public void getNumberOfElementsInList_nullAndemptyList(List<Integer> input) {
	int actualResult = getNumberOfElementsInList(input);

	if (input == null) {
		assertEquals(-1, actualResult);
	} else {
		assertEquals(0, actualResult);
	}

}

Find the below working application.

 

NullAndEmptySourceTest.java

package com.sample.app;

import static org.junit.jupiter.api.Assertions.assertEquals;

import java.util.List;

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.EmptySource;
import org.junit.jupiter.params.provider.NullAndEmptySource;
import org.junit.jupiter.params.provider.NullSource;

public class NullAndEmptySourceTest {

	private static int getNumberOfElementsInList(List<Integer> list) {
		if (list == null) {
			return -1;
		}

		return list.size();
	}

	@ParameterizedTest
	@NullSource
	public void getNumberOfElementsInList_null_negativeOne(List<Integer> input) {
		int actualResult = getNumberOfElementsInList(input);

		assertEquals(-1, actualResult);
	}

	@ParameterizedTest
	@EmptySource
	public void getNumberOfElementsInList_emptyList_negativeOne(List<Integer> input) {
		int actualResult = getNumberOfElementsInList(input);

		assertEquals(0, actualResult);
	}

	@ParameterizedTest
	@NullAndEmptySource
	public void getNumberOfElementsInList_nullAndemptyList(List<Integer> input) {
		int actualResult = getNumberOfElementsInList(input);

		if (input == null) {
			assertEquals(-1, actualResult);
		} else {
			assertEquals(0, actualResult);
		}

	}
}

Run above application, you will see the test result in junit window.

You can also combine @NullSource, @EmptySource, and @ValueSource to test a wider range of null, empty, and blank input.

@ParameterizedTest
@NullAndEmptySource
@ValueSource(strings = { " ", "   ", "\t", "\n", "   \t  " })
void isStringEmptyOrNull_emptyNullCheck(String input) {
	boolean actual = isStringEmptyOrNull(input);

	assertTrue(actual);
}

ParameterizedTest2.java

package com.sample.app;

import static org.junit.jupiter.api.Assertions.assertTrue;

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.NullAndEmptySource;
import org.junit.jupiter.params.provider.ValueSource;

public class ParameterizedTest2 {

	private static boolean isStringEmptyOrNull(String str) {
		return str == null || str.trim().isEmpty();
	}

	@ParameterizedTest
	@NullAndEmptySource
	@ValueSource(strings = { " ", "   ", "\t", "\n", "   \t  " })
	void isStringEmptyOrNull_emptyNullCheck(String input) {
		boolean actual = isStringEmptyOrNull(input);

		assertTrue(actual);
	}
}

 

  

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