Add first visitor test for Java runtime API

runtime-testsuite/pom.xml

@@ -39,7 +39,7 @@
 			<groupId>org.antlr</groupId>
 			<artifactId>antlr4-runtime</artifactId>
 			<version>${project.version}</version>
-			<scope>test</scope>
+			<scope>compile</scope>
 		</dependency>
 		<dependency>
 			<groupId>org.antlr</groupId>
@@ -118,6 +118,22 @@
 					</execution>
 				</executions>
 			</plugin>
+			<plugin>
+				<groupId>org.antlr</groupId>
+				<artifactId>antlr4-maven-plugin</artifactId>
+				<version>${project.version}</version>
+				<executions>
+					<execution>
+						<goals>
+							<goal>antlr4</goal>
+						</goals>
+						<configuration>
+							<sourceDirectory>${basedir}/test</sourceDirectory>
+							<visitor>true</visitor>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
 		</plugins>
 	</build>
 

runtime-testsuite/test/org/antlr/v4/test/runtime/java/api/TestVisitors.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2012-2016 The ANTLR Project. All rights reserved.
+ * Use of this file is governed by the BSD 3-clause license that
+ * can be found in the LICENSE.txt file in the project root.
+ */
+package org.antlr.v4.test.runtime.java.api;
+
+import org.antlr.v4.runtime.ANTLRInputStream;
+import org.antlr.v4.runtime.CommonTokenStream;
+import org.antlr.v4.runtime.tree.AbstractParseTreeVisitor;
+import org.antlr.v4.runtime.tree.TerminalNode;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class TestVisitors {
+
+	/**
+	 * This test verifies the basic behavior of visitors, with an emphasis on
+	 * {@link AbstractParseTreeVisitor#visitTerminal}.
+	 */
+	@Test
+	public void testVisitTerminalNode() {
+		String input = "A";
+		VisitorBasicLexer lexer = new VisitorBasicLexer(new ANTLRInputStream(input));
+		VisitorBasicParser parser = new VisitorBasicParser(new CommonTokenStream(lexer));
+
+		VisitorBasicParser.SContext context = parser.s();
+		Assert.assertEquals("(s A <EOF>)", context.toStringTree(parser));
+
+		VisitorBasicVisitor<String> listener = new VisitorBasicBaseVisitor<String>() {
+			@Override
+			public String visitTerminal(TerminalNode node) {
+				return node.getSymbol().toString() + "\n";
+			}
+
+			@Override
+			protected String defaultResult() {
+				return "";
+			}
+
+			@Override
+			protected String aggregateResult(String aggregate, String nextResult) {
+				return aggregate + nextResult;
+			}
+		};
+
+		String result = listener.visit(context);
+		String expected =
+			"[@0,0:0='A',<1>,1:0]\n" +
+			"[@1,1:0='<EOF>',<-1>,1:1]\n";
+		Assert.assertEquals(expected, result);
+	}
+
+}

runtime-testsuite/test/org/antlr/v4/test/runtime/java/api/VisitorBasic.g4

@@ -0,0 +1,5 @@
+grammar VisitorBasic;
+
+s
+	:	'A' EOF
+	;