Argument Aggregation in Parameterized Tests in Junit 5

This post talks about Argument Aggregation supports provided by JUnit Jupiter in the case of @ParameterizedTest

By default, each argument provided to a @ParameterizedTest method corresponds to a single method parameter. Consequently, argument sources that are expected to supply a large number of arguments can lead to large method signatures.

In that case, an ArgumentsAccessor may be used instead of multiple parameters. Using this API, you can access the provided arguments through a single argument passed to your test method. In addition, type conversion is supported.

Let’s try to understand the above concept using a demo project

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.kkjavatutorials</groupId>
  <artifactId>JUnit5ArgumentAggregationInParameterizedTestsExample</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  
  	<properties>
		<maven.compiler.target>8</maven.compiler.target>
		<maven.compiler.source>8</maven.compiler.source>
		<junit.jupiter.version>5.6.2</junit.jupiter.version>
	</properties>

	<dependencies>

		<dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter-api</artifactId>
			<version>${junit.jupiter.version}</version>
			<scope>test</scope>
		</dependency>

		<dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter-engine</artifactId>
			<version>${junit.jupiter.version}</version>
			<scope>test</scope>
		</dependency>

		<dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter-params</artifactId>
			<version>${junit.jupiter.version}</version>
			<scope>test</scope>
		</dependency>

	</dependencies>
</project>

<groupId>com.kkjavatutorials</groupId>

<artifactId>JUnit5ArgumentAggregationInParameterizedTestsExample</artifactId>

<version>0.0.1-SNAPSHOT</version>

<maven.compiler.target>8</maven.compiler.target>

<maven.compiler.source>8</maven.compiler.source>

<junit.jupiter.version>5.6.2</junit.jupiter.version>

</properties>

<groupId>org.junit.jupiter</groupId>

<artifactId>junit-jupiter-api</artifactId>

<version>${junit.jupiter.version}</version>

</dependency>

<groupId>org.junit.jupiter</groupId>

<artifactId>junit-jupiter-engine</artifactId>

<version>${junit.jupiter.version}</version>

</dependency>

<groupId>org.junit.jupiter</groupId>

<artifactId>junit-jupiter-params</artifactId>

<version>${junit.jupiter.version}</version>

</dependency>

</dependencies>

</project>

Gender.java

package com.kkjavatutorials.model;

public enum Gender {
 M,F
}

package com.kkjavatutorials.model;

public enum Gender {

M,F

}

Person.java

package com.kkjavatutorials.model;

import java.time.LocalDate;

public class Person {

	private String firstName;
	private String lastName;
	private Gender gender;
	private LocalDate dateOfBirth;
	
	public Person(String firstName, String lastName, Gender gender, LocalDate dateOfBirth) {
		super();
		this.firstName = firstName;
		this.lastName = lastName;
		this.gender = gender;
		this.dateOfBirth = dateOfBirth;
	}
	
	public String getFirstName() {
		return firstName;
	}
	public String getLastName() {
		return lastName;
	}
	public Gender getGender() {
		return gender;
	}
	public LocalDate getDateOfBirth() {
		return dateOfBirth;
	}
}

package com.kkjavatutorials.model;

import java.time.LocalDate;

public class Person {

private String firstName;

private String lastName;

private Gender gender;

private LocalDate dateOfBirth;

public Person(String firstName, String lastName, Gender gender, LocalDate dateOfBirth) {

super();

this.firstName = firstName;

this.lastName = lastName;

this.gender = gender;

this.dateOfBirth = dateOfBirth;

}

public String getFirstName() {

return firstName;

}

public String getLastName() {

return lastName;

}

public Gender getGender() {

return gender;

}

public LocalDate getDateOfBirth() {

return dateOfBirth;

}

CsvToPerson.java

package com.kkjavatutorials;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.junit.jupiter.params.aggregator.AggregateWith;

import com.kkjavatutorials.ArgumentAggregationInParameterizedTest.PersonAggregator;

@Retention(value = RetentionPolicy.RUNTIME)
@Target(value = { ElementType.PARAMETER })
@AggregateWith(PersonAggregator.class)
public @interface CsvToPerson {
}

package com.kkjavatutorials;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

import org.junit.jupiter.params.aggregator.AggregateWith;

import com.kkjavatutorials.ArgumentAggregationInParameterizedTest.PersonAggregator;

@Retention(value = RetentionPolicy.RUNTIME)

@Target(value = { ElementType.PARAMETER })

@AggregateWith(PersonAggregator.class)

public @interface CsvToPerson {

}

ArgumentAggregationInParameterizedTest.java

package com.kkjavatutorials;

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

import java.time.LocalDate;

import org.junit.jupiter.api.extension.ParameterContext;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.aggregator.AggregateWith;
import org.junit.jupiter.params.aggregator.ArgumentsAccessor;
import org.junit.jupiter.params.aggregator.ArgumentsAggregator;
import org.junit.jupiter.params.provider.CsvSource;

import com.kkjavatutorials.model.Gender;
import com.kkjavatutorials.model.Person;

public class ArgumentAggregationInParameterizedTest {

	/**
	 * Argument Aggregation in ParameterizedTest
	 * @param argumentsAccessor
	 */
	@ParameterizedTest
	@CsvSource({ "Jane, Doe, F, 1995-05-20", "John, Doe, M, 1995-10-22" })
	void testWithArgumentsAccessor(ArgumentsAccessor argumentsAccessor) {
	    Person person = new Person(argumentsAccessor.getString(0),
	                               argumentsAccessor.getString(1),
	                               argumentsAccessor.get(2, Gender.class),
	                               argumentsAccessor.get(3, LocalDate.class));

	    if (person.getFirstName().equals("Jane")) {
	        assertEquals(Gender.F, person.getGender());
	    }
	    else {
	        assertEquals(Gender.M, person.getGender());
	    }
	    assertEquals("Doe", person.getLastName());
	    assertEquals(1995, person.getDateOfBirth().getYear());
	}
	
	/**
	 * Custom Aggregator in in ParameterizedTest
	 * @param person
	 */
	@ParameterizedTest
	@CsvSource({ "Jane, Doe, F, 1991-05-20", "John, Doe, M, 1991-10-22" })
	void testWithArgumentsAggregator(@AggregateWith(PersonAggregator.class) Person person) {
		assertEquals("Doe", person.getLastName());
		assertEquals(1991, person.getDateOfBirth().getYear());
	}
	
	/**
	 * Custom Aggregator & annotation in in ParameterizedTest
	 * @param person
	 */
	@ParameterizedTest
	@CsvSource({ "Jane, Doe, F, 1992-06-22", "John, Doe, M, 1992-10-25","Sean, Doe, M, 1992-01-20" })
	void testWithCustomAggregatorAnnotation(@CsvToPerson Person person) {
		assertEquals("Doe", person.getLastName());
		assertEquals(1992, person.getDateOfBirth().getYear());
	}
	
	/**
	 * @author KK JavaTutorials
	 * Custom Aggregator class
	 * You should Note that an implementation of ArgumentsAggregator class must be declared as either 
	 * a topmost class or as a static inner/nested class
	 */
	public static class PersonAggregator implements ArgumentsAggregator {
	    @Override
	    public Person aggregateArguments(ArgumentsAccessor argumentsAccessor, ParameterContext parameterContext) {
	        return new Person(argumentsAccessor.getString(0),
	                          argumentsAccessor.getString(1),
	                          argumentsAccessor.get(2, Gender.class),
	                          argumentsAccessor.get(3, LocalDate.class));
	    }
	}
}

package com.kkjavatutorials;

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

import java.time.LocalDate;

import org.junit.jupiter.api.extension.ParameterContext;

import org.junit.jupiter.params.ParameterizedTest;

import org.junit.jupiter.params.aggregator.AggregateWith;

import org.junit.jupiter.params.aggregator.ArgumentsAccessor;

import org.junit.jupiter.params.aggregator.ArgumentsAggregator;

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

import com.kkjavatutorials.model.Gender;

import com.kkjavatutorials.model.Person;

public class ArgumentAggregationInParameterizedTest {

/**

* Argument Aggregation in ParameterizedTest

* @param argumentsAccessor

@ParameterizedTest

@CsvSource({ "Jane, Doe, F, 1995-05-20", "John, Doe, M, 1995-10-22" })

void testWithArgumentsAccessor(ArgumentsAccessor argumentsAccessor) {

Person person = new Person(argumentsAccessor.getString(0),

argumentsAccessor.getString(1),

argumentsAccessor.get(2, Gender.class),

argumentsAccessor.get(3, LocalDate.class));

if (person.getFirstName().equals("Jane")) {

assertEquals(Gender.F, person.getGender());

}

else {

assertEquals(Gender.M, person.getGender());

}

assertEquals("Doe", person.getLastName());

assertEquals(1995, person.getDateOfBirth().getYear());

}

/**

* Custom Aggregator in in ParameterizedTest

* @param person

@ParameterizedTest

@CsvSource({ "Jane, Doe, F, 1991-05-20", "John, Doe, M, 1991-10-22" })

void testWithArgumentsAggregator(@AggregateWith(PersonAggregator.class) Person person) {

assertEquals("Doe", person.getLastName());

assertEquals(1991, person.getDateOfBirth().getYear());

}

/**

* Custom Aggregator & annotation in in ParameterizedTest

* @param person

@ParameterizedTest

@CsvSource({ "Jane, Doe, F, 1992-06-22", "John, Doe, M, 1992-10-25","Sean, Doe, M, 1992-01-20" })

void testWithCustomAggregatorAnnotation(@CsvToPerson Person person) {

assertEquals("Doe", person.getLastName());

assertEquals(1992, person.getDateOfBirth().getYear());

}

/**

* @author KK JavaTutorials

* Custom Aggregator class

* You should Note that an implementation of ArgumentsAggregator class must be declared as either

* a topmost class or as a static inner/nested class

public static class PersonAggregator implements ArgumentsAggregator {

@Override

public Person aggregateArguments(ArgumentsAccessor argumentsAccessor, ParameterContext parameterContext) {

return new Person(argumentsAccessor.getString(0),

argumentsAccessor.getString(1),

argumentsAccessor.get(2, Gender.class),

argumentsAccessor.get(3, LocalDate.class));

}

The output of the above project:

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