[IO- 889] Add test for Tailer close() (#842)

* [IO-856] Try test on all OSs for GitHub CI

* [IO-889] Tailer.close() does not guarantee file close

- Add test class
- Green on macOS locally

* [IO-889] Tailer.close() does not guarantee file close

- Add test class
- Green on macOS locally
- Fails on Windows on GH CI

Author: garydgregory

src/test/java/org/apache/commons/io/input/TailerCloseTest.java

@@ -0,0 +1,98 @@
+/*
+ * 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
+ *
+ *      https://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.commons.io.input;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.DisabledOnOs;
+import org.junit.jupiter.api.condition.OS;
+
+/**
+ * Tests {@link Tailer} for <a href=https://issues.apache.org/jira/browse/IO-889">IO-889</a>.
+ */
+public class TailerCloseTest {
+
+    private class TailerTestListener extends TailerListenerAdapter {
+
+        @Override
+        public void handle(final Exception ex) {
+            super.handle(ex);
+            result.completeExceptionally(ex);
+        }
+
+        @Override
+        public void handle(final String line) {
+            super.handle(line);
+            result.complete(line);
+        }
+    }
+
+    private static Thread newDaemonThread(final Runnable runnable) {
+        final Thread thread = new Thread(runnable, "commons-io-tailer");
+        thread.setDaemon(true);
+        return thread;
+    }
+
+    private ExecutorService executorService;
+    private Path path;
+    private final CompletableFuture<String> result = new CompletableFuture<>();
+
+    @AfterEach
+    public void tearDown() throws Exception {
+        // wait for the tailer task and delete log file if previous delete failed
+        if (executorService != null) {
+            executorService.shutdown();
+            executorService.awaitTermination(60, TimeUnit.SECONDS);
+        }
+        if (path != null && Files.exists(path)) {
+            Files.delete(path);
+        }
+    }
+
+    @DisabledOnOs(value = OS.WINDOWS)
+    @Test
+    public void testCloseTailer() throws Exception {
+        path = Files.createTempFile("TailerTestFile", ".log");
+        // same as default Tailer executor
+        executorService = Executors.newSingleThreadExecutor(TailerCloseTest::newDaemonThread);
+        try (
+        // @formatter:off
+            Tailer tailer = Tailer
+                    .builder()
+                    .setExecutorService(executorService)
+                    .setTailerListener(new TailerTestListener())
+                    .setFile(path.toFile())
+                    .get()) {
+            // @formatter:on
+            Files.write(path, "aaa\n".getBytes());
+            // wait for the background thread to open the file
+            assertEquals("aaa", result.get(60, TimeUnit.SECONDS));
+        }
+        // delete file after closing Tailer
+        Files.delete(path);
+    }
+}