add a brief test of the subtree output tool

test/src/edu/stanford/nlp/trees/OutputSubtreesTest.java

@@ -0,0 +1,48 @@
+package edu.stanford.nlp.trees;
+
+import static org.junit.Assert.assertArrayEquals;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import edu.stanford.nlp.io.IOUtils;
+
+public class OutputSubtreesTest {
+  public Path tmpDir;
+
+  @Before
+  public void makeTmpDir() throws IOException {
+    tmpDir = Files.createTempDirectory("output");
+    tmpDir.toFile().deleteOnExit();
+  }
+
+  String[] EXPECTED = {"1   In this case zero .",
+                       "2   In this",
+                       "2   In",
+                       "2   this",
+                       "1   case zero .",
+                       "2   case",
+                       "1   zero .",
+                       "1   zero",
+                       "2   ."};
+
+
+  @Test
+  public void testSingleTree() throws IOException {
+    String inputFilename = tmpDir + File.separator + "input.txt";
+    IOUtils.writeStringToFile("(1 (2 (2 In) (2 this)) (1 (2 case) (1 (1 zero) (2 .))))", inputFilename, "utf-8");
+
+    String outputFilename = tmpDir + File.separator + "output.txt";    
+    String[] args = {"-input", inputFilename, "-output", outputFilename};
+    OutputSubtrees.main(args);
+
+    String[] results = IOUtils.slurpFile(outputFilename).trim().split("\n");
+    assertArrayEquals(EXPECTED, results);
+  }
+}