Allow ArgumentsAggregator implementations to use constructor injection

Issue: #4018

Author: marcphilipp

junit-jupiter-params/src/main/java/org/junit/jupiter/params/ParameterizedTestMethodContext.java

@@ -32,7 +32,6 @@
 import org.junit.jupiter.params.converter.DefaultArgumentConverter;
 import org.junit.jupiter.params.support.AnnotationConsumerInitializer;
 import org.junit.platform.commons.support.AnnotationSupport;
-import org.junit.platform.commons.support.ReflectionSupport;
 import org.junit.platform.commons.util.StringUtils;
 
 /**
@@ -200,7 +199,7 @@ Resolver createResolver(ParameterContext parameterContext, ExtensionContext exte
 				try { // @formatter:off
 					return AnnotationSupport.findAnnotation(parameterContext.getParameter(), AggregateWith.class)
 							.map(AggregateWith::value)
-							.map(clazz -> (ArgumentsAggregator) ReflectionSupport.newInstance(clazz))
+							.map(clazz -> ParameterizedTestSpiInstantiator.instantiate(ArgumentsAggregator.class, clazz, extensionContext))
 							.map(Aggregator::new)
 							.orElse(Aggregator.DEFAULT);
 				} // @formatter:on

junit-jupiter-params/src/main/java/org/junit/jupiter/params/aggregator/ArgumentsAggregator.java

@@ -14,6 +14,7 @@
 
 import org.apiguardian.api.API;
 import org.junit.jupiter.api.extension.ParameterContext;
+import org.junit.jupiter.api.extension.ParameterResolver;
 
 /**
  * {@code ArgumentsAggregator} is an abstraction for the aggregation of arguments
@@ -33,10 +34,11 @@
  * in a CSV file into a domain object such as a {@code Person}, {@code Address},
  * {@code Order}, etc.
  *
- * <p>Implementations must provide a no-args constructor and should not make any
- * assumptions regarding when they are instantiated or how often they are called.
- * Since instances may potentially be cached and called from different threads,
- * they should be thread-safe and designed to be used as singletons.
+ * <p>Implementations must provide a no-args constructor or a single unambiguous
+ * constructor to use {@linkplain ParameterResolver parameter resolution}. They
+ * should not make any assumptions regarding when they are instantiated or how
+ * often they are called. Since instances may potentially be cached and called
+ * from different threads, they should be thread-safe.
  *
  * @since 5.2
  * @see AggregateWith

jupiter-tests/src/test/java/org/junit/jupiter/params/ParameterizedTestIntegrationTests.java

@@ -1225,6 +1225,13 @@ void injectsParametersIntoArgumentConverterConstructor() {
 					.testEvents() //
 					.assertStatistics(it -> it.succeeded(1));
 		}
+
+		@Test
+		void injectsParametersIntoArgumentsAggregatorConstructor() {
+			execute(SpiParameterInjectionTestCase.class, "argumentsAggregatorWithConstructorParameter", String.class) //
+					.testEvents() //
+					.assertStatistics(it -> it.succeeded(1));
+		}
 	}
 
 	// -------------------------------------------------------------------------
@@ -2176,6 +2183,13 @@ void argumentConverterWithConstructorParameter(
 			assertEquals("resolved value", argument);
 		}
 
+		@ParameterizedTest
+		@ValueSource(strings = "value")
+		void argumentsAggregatorWithConstructorParameter(
+				@AggregateWith(ArgumentsAggregatorWithConstructorParameter.class) String argument) {
+			assertEquals("resolved value", argument);
+		}
+
 		record ArgumentsProviderWithConstructorParameter(String value) implements ArgumentsProvider {
 
 			@Override
@@ -2191,6 +2205,15 @@ public Object convert(Object source, ParameterContext context) throws ArgumentCo
 				return value;
 			}
 		}
+
+		record ArgumentsAggregatorWithConstructorParameter(String value) implements ArgumentsAggregator {
+
+			@Override
+			public Object aggregateArguments(ArgumentsAccessor accessor, ParameterContext context)
+					throws ArgumentsAggregationException {
+				return value;
+			}
+		}
 	}
 
 	private static class TwoSingleStringArgumentsProvider implements ArgumentsProvider {