ParameterResolver defines the API for Extensions that wish to dynamically resolve parameters at runtime for test constructors or methods.

Java source and doc

Definition of ParameterResolver

 package org.junit.jupiter.api.extension;
 @API(status = STABLE, since = "5.0")
 public interface ParameterResolver extends TestInstantiationAwareExtension {
     boolean supportsParameter(ParameterContext parameterContext, 1
                               ExtensionContext extensionContext)
                               throws ParameterResolutionException;
     Object resolveParameter(ParameterContext parameterContext, 2
                             ExtensionContext extensionContext)
                             throws ParameterResolutionException;
 }

We have already seen an example in our Introduction to JUnit Extension tutorial, let's see another example here.

Example

package com.logicbig.example;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.*;

@ExtendWith(ParameterResolverTest.CustomResolver.class)
public class ParameterResolverTest {

    @Test
    void testInjection(String data) {
        System.out.println("received: " + data);
    }

    static class CustomResolver implements ParameterResolver {
        @Override
        public boolean supportsParameter(ParameterContext pc, ExtensionContext ec) {
            return pc.getParameter().getType() == String.class;
        }
        @Override
        public Object resolveParameter(ParameterContext pc, ExtensionContext ec) {
            return "hello world";
        }
    }
}

Output

$ mvn test -Dtest=ParameterResolverTest
[INFO] Scanning for projects...
[INFO] 
[INFO] ------< com.logicbig.example:junit-5-parameter-resolver-example >-------
[INFO] Building junit-5-parameter-resolver-example 1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- resources:3.3.1:resources (default-resources) @ junit-5-parameter-resolver-example ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory D:\example-projects\junit-5\junit-5-extensions\junit-5-parameter-resolver-example\src\main\resources
[INFO] 
[INFO] --- compiler:3.13.0:compile (default-compile) @ junit-5-parameter-resolver-example ---
[INFO] No sources to compile
[INFO] 
[INFO] --- resources:3.3.1:testResources (default-testResources) @ junit-5-parameter-resolver-example ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory D:\example-projects\junit-5\junit-5-extensions\junit-5-parameter-resolver-example\src\test\resources
[INFO] 
[INFO] --- compiler:3.13.0:testCompile (default-testCompile) @ junit-5-parameter-resolver-example ---
[INFO] Recompiling the module because of changed source code.
[WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent!
[INFO] Compiling 1 source file with javac [debug target 1.8] to target\test-classes
[WARNING] bootstrap class path is not set in conjunction with -source 8
  not setting the bootstrap class path may lead to class files that cannot run on JDK 8
    --release 8 is recommended instead of -source 8 -target 1.8 because it sets the bootstrap class path automatically
[WARNING] source value 8 is obsolete and will be removed in a future release
[WARNING] target value 8 is obsolete and will be removed in a future release
[WARNING] To suppress warnings about obsolete options, use -Xlint:-options.
[INFO] 
[INFO] --- surefire:3.2.5:test (default-test) @ junit-5-parameter-resolver-example ---
[INFO] Using auto detected provider org.apache.maven.surefire.junitplatform.JUnitPlatformProvider
[INFO] 
[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running com.logicbig.example.ParameterResolverTest
received: hello world
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.058 s -- in com.logicbig.example.ParameterResolverTest
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  3.037 s
[INFO] Finished at: 2025-12-30T16:04:42+08:00
[INFO] ------------------------------------------------------------------------

The successful execution of the test shows that a String value was injected directly into the test method signature. This proves that ParameterResolver allows for powerful, type-based dependency injection, enabling tests to receive required data or services without manual instantiation.

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
  ×

  Version compatibilities of junit-jupiter-engine with this example:

  • 5.0.0
  • 5.0.1
  • 5.0.2
  • 5.0.3
  • 5.1.0
  • 5.1.1
  • 5.2.0
  • 5.3.0
  • 5.3.1
  • 5.3.2
  • 5.4.0
  • 5.4.1
  • 5.4.2
  • 5.5.0
  • 5.5.1
  • 5.5.2
  • 5.6.0
  • 5.6.1
  • 5.6.2
  • 5.6.3
  • 5.7.0
  • 5.7.1
  • 5.7.2
  • 5.8.0
  • 5.8.1
  • 5.8.2
  • 5.9.0
  • 5.9.1
  • 5.9.2
  • 5.9.3
  • 5.10.0
  • 5.10.1
  • 5.10.2
  • 5.10.3
  • 5.10.4
  • 5.10.5
  • 5.11.0
  • 5.11.1
  • 5.11.2
  • 5.11.3
  • 5.11.4
  • 5.12.0
  • 5.12.1
  • 5.12.2
  • 5.13.0
  • 5.13.1
  • 5.13.2
  • 5.13.3
  • 5.13.4
  • 5.14.0
  • 5.14.1
  • 6.0.0
  • 6.0.1

  Versions in green have been tested.

• JDK 25
• Maven 3.9.11