Use a custom SimpleArgumentConverter and annotate the parameter with @ConvertWith in a @ParameterizedTest to transform input values.

Java source and doc

public abstract class SimpleArgumentConverter {

    // Convert the supplied source object into the supplied target type.
    protected abstract Object convert(Object source, Class<?> targetType)
                                              throws ArgumentConversionException;

}

Example Project

package com.logicbig.example;

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.converter.ConvertWith;
import org.junit.jupiter.params.converter.SimpleArgumentConverter;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;

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

public class ParameterizedSimpleArgumentConverterTest {

    static class StringToLocalDateConverter extends SimpleArgumentConverter {
        @Override
        protected Object convert(Object source, Class<?> targetType) {
            if (source == null) return null;
            if (!LocalDate.class.equals(targetType)) {
                throw new IllegalArgumentException("Conversion target must be LocalDate");
            }
            return LocalDate.parse(source.toString(), DateTimeFormatter.ISO_LOCAL_DATE);
        }
    }

    @ParameterizedTest(name = "#{index} parsed date: {0}")
    @org.junit.jupiter.params.provider.ValueSource(strings = {"2024-01-01", "2025-12-04"})
    void convertStringToLocalDate(@ConvertWith(StringToLocalDateConverter.class) LocalDate date) {
        // verify round-trip formatting
        assertEquals(date, LocalDate.parse(date.toString()));
    }
}

mvn test -Dtest=ParameterizedSimpleArgumentConverterTest

Output

D:\example-projects\junit-5\junit-5-parameterized-tests\junit-5-parameterized-simpleargumentconverter>mvn test -Dtest=ParameterizedSimpleArgumentConverterTest
[INFO] Scanning for projects...
[INFO] 
[INFO] --< com.logicbig.example:junit-5-parameterized-simpleargumentconverter >--
[INFO] Building junit-5-parameterized-simpleargumentconverter 1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- resources:3.3.1:resources (default-resources) @ junit-5-parameterized-simpleargumentconverter ---
[INFO] skip non existing resourceDirectory D:\example-projects\junit-5\junit-5-parameterized-tests\junit-5-parameterized-simpleargumentconverter\src\main\resources
[INFO] 
[INFO] --- compiler:3.14.1:compile (default-compile) @ junit-5-parameterized-simpleargumentconverter ---
[INFO] No sources to compile
[INFO] 
[INFO] --- resources:3.3.1:testResources (default-testResources) @ junit-5-parameterized-simpleargumentconverter ---
[INFO] skip non existing resourceDirectory D:\example-projects\junit-5\junit-5-parameterized-tests\junit-5-parameterized-simpleargumentconverter\src\test\resources
[INFO] 
[INFO] --- compiler:3.14.1:testCompile (default-testCompile) @ junit-5-parameterized-simpleargumentconverter ---
[INFO] Recompiling the module because of changed source code.
[INFO] Compiling 1 source file with javac [debug target 25] to target\test-classes
[INFO] 
[INFO] --- surefire:3.5.0:test (default-test) @ junit-5-parameterized-simpleargumentconverter ---
[INFO] Using auto detected provider org.apache.maven.surefire.junitplatform.JUnitPlatformProvider
[INFO] 
[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] +--com.logicbig.example.ParameterizedSimpleArgumentConverterTest - 0.209 ss
[INFO] |  +-- [OK] convertStringToLocalDate(LocalDate) #1 parsed date: "2024-01-01" - 0.070 ss
[INFO] |  '-- [OK] convertStringToLocalDate(LocalDate) #2 parsed date: "2025-12-04" - 0.003 ss
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 2, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  3.387 s
[INFO] Finished at: 2025-12-04T15:04:16+08:00
[INFO] ------------------------------------------------------------------------

Example Project

Dependencies and Technologies Used:

• junit-jupiter-engine 6.0.1 (Module "junit-jupiter-engine" of JUnit)
   Version Compatibility: 5.0.0 - 6.0.1Version List
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  Version compatibilities of junit-jupiter-engine with this example:

  • 5.0.0
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  • 5.1.1
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  • 5.14.0
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  • 6.0.0
  • 6.0.1

  Versions in green have been tested.

• junit-jupiter-params 6.0.1 (Module "junit-jupiter-params" of JUnit)
  
• JDK 25
• Maven 3.9.11