ORC-1632: Add test for count command

### What changes were proposed in this pull request?
Add unit test for `count` command of `orc-tools`.

### Why are the changes needed?
Improve code test coverage and avoid regressions.

### How was this patch tested?
Add UT.

### Was this patch authored or co-authored using generative AI tooling?
No

Closes #1817 from cxzl25/ORC-1632.

Authored-by: sychen <sychen@ctrip.com>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

java/tools/src/test/org/apache/orc/tools/count/TestRowCount.java

@@ -0,0 +1,94 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.orc.tools.count;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hive.ql.exec.vector.LongColumnVector;
+import org.apache.hadoop.hive.ql.exec.vector.VectorizedRowBatch;
+import org.apache.orc.OrcFile;
+import org.apache.orc.TypeDescription;
+import org.apache.orc.Writer;
+import org.apache.orc.tools.RowCount;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Paths;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class TestRowCount {
+  private Path workDir = new Path(
+      Paths.get(System.getProperty("test.tmp.dir"), "orc-test-count").toString());
+  private Configuration conf;
+  private FileSystem fs;
+
+  @BeforeEach
+  public void openFileSystem() throws Exception {
+    conf = new Configuration();
+    fs = FileSystem.getLocal(conf);
+    fs.setWorkingDirectory(workDir);
+    fs.mkdirs(workDir);
+    fs.deleteOnExit(workDir);
+  }
+
+  @Test
+  public void testCount() throws Exception {
+    TypeDescription schema = TypeDescription.fromString("struct<x:int>");
+    Map<String, Integer> fileToRowCountMap = new LinkedHashMap<>();
+    fileToRowCountMap.put("test-count-1.orc", 10000);
+    fileToRowCountMap.put("test-count-2.orc", 20000);
+    for (Map.Entry<String, Integer> fileToRowCount : fileToRowCountMap.entrySet()) {
+      Writer writer = OrcFile.createWriter(new Path(fileToRowCount.getKey()),
+          OrcFile.writerOptions(conf)
+              .setSchema(schema));
+      VectorizedRowBatch batch = schema.createRowBatch();
+      LongColumnVector x = (LongColumnVector) batch.cols[0];
+      for (int r = 0; r < fileToRowCount.getValue(); ++r) {
+        int row = batch.size++;
+        x.vector[row] = r;
+        if (batch.size == batch.getMaxSize()) {
+          writer.addRowBatch(batch);
+          batch.reset();
+        }
+      }
+      if (batch.size != 0) {
+        writer.addRowBatch(batch);
+      }
+      writer.close();
+    }
+
+    PrintStream origOut = System.out;
+    ByteArrayOutputStream myOut = new ByteArrayOutputStream();
+    // replace stdout and run command
+    System.setOut(new PrintStream(myOut, false, StandardCharsets.UTF_8));
+    RowCount.main(conf, new String[]{workDir.toString()});
+    System.out.flush();
+    System.setOut(origOut);
+    String output = myOut.toString(StandardCharsets.UTF_8);
+    assertTrue(output.contains(" 10000"));
+    assertTrue(output.contains(" 20000"));
+  }
+}