Improve test robustness

Signed-off-by: Matt Sicker <boards@gmail.com>

core/src/test/java/jenkins/util/io/PathRemoverTest.java

@@ -34,7 +34,14 @@ import org.junit.rules.Timeout;
 import java.io.File;
 import java.io.FileWriter;
 import java.io.IOException;
+import java.io.UncheckedIOException;
 import java.nio.file.Files;
+import java.nio.file.NoSuchFileException;
+import java.nio.file.Path;
+import java.nio.file.attribute.PosixFileAttributes;
+import java.nio.file.attribute.PosixFilePermission;
+import java.util.Arrays;
+import java.util.Set;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -78,18 +85,35 @@ public class PathRemoverTest {
 
     @Test
     public void testForceRemoveFile_ReadOnly() throws IOException {
-        File dir = tmp.newFolder();
-        File file = new File(dir, "file.tmp");
-        touchWithFileName(file);
-        file.setWritable(false);
-        dir.setWritable(false);
-        assertFalse("Unable to make file read-only: " + file, Files.isWritable(file.toPath()));
-        assertFalse("Unable to make directory read-only: " + dir, Files.isWritable(dir.toPath()));
+        Path dir = Files.createTempDirectory("remover");
+        Path file = dir.resolve("file.tmp");
+        touchWithFileName(file.toFile());
+        makeReadOnly(file);
+        makeReadOnly(dir);
+        assertFalse("Unable to make file read-only: " + file, Files.isWritable(file));
+        assertFalse("Unable to make directory read-only: " + dir, Files.isWritable(dir));
 
         PathRemover remover = PathRemover.newSimpleRemover();
-        remover.forceRemoveFile(file.toPath());
+        remover.forceRemoveFile(file);
 
-        assertFalse("Unable to delete file: " + file, file.exists());
+        assertTrue("Unable to delete file: " + file, Files.notExists(file));
+    }
+
+    private static void makeReadOnly(Path path) {
+        try {
+            PosixFileAttributes attrs = Files.readAttributes(path, PosixFileAttributes.class);
+            Set<PosixFilePermission> permissions = attrs.permissions();
+            permissions.removeAll(Arrays.asList(PosixFilePermission.OWNER_WRITE, PosixFilePermission.GROUP_WRITE, PosixFilePermission.OTHERS_WRITE));
+            Files.setPosixFilePermissions(path, permissions);
+        } catch (NoSuchFileException ignored) {
+            return;
+        } catch (UnsupportedOperationException ignored) {
+            // retry with setWritable
+        } catch (IOException e) {
+            throw new UncheckedIOException(e);
+        }
+        // fallback method for filesystems that don't support POSIX attributes
+        path.toFile().setWritable(false);
     }
 
     @Test