Test status quo for void function references in SpEL

spring-expression/src/test/java/org/springframework/expression/spel/SpelCompilationCoverageTests.java

@@ -29,6 +29,8 @@ import java.util.Set;
 import java.util.StringTokenizer;
 
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 import org.springframework.asm.MethodVisitor;
 import org.springframework.expression.AccessException;
@@ -55,6 +57,7 @@ import static org.assertj.core.api.InstanceOfAssertFactories.BOOLEAN;
  * Checks SpelCompiler behavior. This should cover compilation all compiled node types.
  *
  * @author Andy Clement
+ * @author Sam Brannen
  * @since 4.1
  */
 public class SpelCompilationCoverageTests extends AbstractExpressionTests {
@@ -997,6 +1000,60 @@ public class SpelCompilationCoverageTests extends AbstractExpressionTests {
 		assertThat(expression.getValue(ctx).toString()).isEqualTo("4.0");
 	}
 
+	@ParameterizedTest
+	@ValueSource(strings = {"voidMethod", "voidWrapperMethod"})
+	public void voidFunctionReference(String method) throws Exception {
+		assertVoidFunctionReferenceBehavior(method);
+	}
+
+	private void assertVoidFunctionReferenceBehavior(String methodName) throws Exception {
+		Method method = getClass().getDeclaredMethod(methodName, String.class);
+
+		EvaluationContext ctx = new StandardEvaluationContext();
+		ctx.setVariable("voidMethod", method);
+
+		expression = parser.parseExpression("#voidMethod('a')");
+
+		voidMethodInvokedWith = null;
+		expression.getValue(ctx);
+		assertThat(voidMethodInvokedWith).isEqualTo("a");
+		assertCanCompile(expression);
+
+		voidMethodInvokedWith = null;
+		expression.getValue(ctx);
+		assertThat(voidMethodInvokedWith).isEqualTo("a");
+		assertCanCompile(expression);
+
+		voidMethodInvokedWith = null;
+		expression.getValue(ctx);
+		assertThat(voidMethodInvokedWith).isEqualTo("a");
+		assertCanCompile(expression);
+
+		expression = parser.parseExpression("#voidMethod(#a)");
+		ctx.setVariable("a", "foo");
+
+		voidMethodInvokedWith = null;
+		expression.getValue(ctx);
+		assertThat(voidMethodInvokedWith).isEqualTo("foo");
+		assertCanCompile(expression);
+
+		voidMethodInvokedWith = null;
+		expression.getValue(ctx);
+		assertThat(voidMethodInvokedWith).isEqualTo("foo");
+		assertCanCompile(expression);
+	}
+
+	private static String voidMethodInvokedWith;
+
+	public static Void voidWrapperMethod(String str) {
+		voidMethodInvokedWith = str;
+		return null;
+	}
+
+	public static void voidMethod(String str) {
+		voidMethodInvokedWith = str;
+	}
+
 	@Test
 	public void functionReferenceVisibility_SPR12359() throws Exception {
 		// Confirms visibility of what is being called.