chimera: fix unit tests

Two unit tests are racy because they assume at least 1 ms has elapsed
between two calls to stat.  This patch has the testing thread sleep
for a millisecond to ensure this is true.

The patch also alters how the directory listing helper handles invalid
situations, with it throwing an exception rather than logging an error.
This allows the unit-test that checks this behaviour to do so without
logging the error.

Target: master
Request: 2.10
Request: 2.9
Request: 2.8
Request: 2.7
Request: 2.6

Conflicts:
	modules/chimera/src/main/java/org/dcache/chimera/DirectoryStreamHelper.java
	modules/chimera/src/test/java/org/dcache/chimera/DirectoryStreamHelperTest.java

modules/chimera/src/main/java/org/dcache/chimera/DirectoryStreamHelper.java

@@ -30,7 +30,15 @@ public class DirectoryStreamHelper {
      */
     public static List<HimeraDirectoryEntry> listOf(FsInode inode) throws IOException, IOHimeraFsException {
 
-        List<HimeraDirectoryEntry> directoryList = new ArrayList<>(inode.statCache().getNlink());
+        List<HimeraDirectoryEntry> directoryList;
+
+        int estimatedListSize = inode.statCache().getNlink();
+        if (estimatedListSize < 0) {
+            throw new RuntimeException("Invalid nlink count for directory: " + inode);
+        } else {
+            directoryList = new ArrayList<>(estimatedListSize);
+        }
+
         try (DirectoryStreamB<HimeraDirectoryEntry> dirStream =
                 inode.newDirectoryStream()) {
             for (HimeraDirectoryEntry e : dirStream) {

modules/chimera/src/test/java/org/dcache/chimera/BasicTest.java

@@ -171,6 +171,8 @@ public void testDeleteFile() throws Exception {
         base.create("testCreateFile", 0, 0, 0644);
         Stat stat = base.stat();
 
+        Thread.sleep(1); // ensure updated directory mtime is distinct from creation mtime
+
         base.remove("testCreateFile");
 
         assertEquals("remove have to decrease parents link count", base.stat().getNlink(), stat.getNlink() - 1);
@@ -186,6 +188,8 @@ public void testDeleteDir() throws Exception {
         base.create("testCreateDir", 0, 0, 0644);
         Stat stat = base.stat();
 
+        Thread.sleep(1); // ensure updated directory mtime is distinct from creation mtime
+
         base.remove("testCreateDir");
 
         assertEquals("remove have to decrease parents link count", base.stat().getNlink(), stat.getNlink() - 1);

modules/chimera/src/test/java/org/dcache/chimera/DirectoryStreamHelperTest.java

@@ -0,0 +1,54 @@
+/*
+ * This library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this program (see the file COPYING.LIB for more
+ * details); if not, write to the Free Software Foundation, Inc.,
+ * 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+package org.dcache.chimera;
+
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.Collections;
+import java.util.Iterator;
+
+import org.dcache.chimera.posix.Stat;
+
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.*;
+
+public class DirectoryStreamHelperTest {
+
+    @Test(expected=RuntimeException.class)
+    public void testNegativeNlink() throws ChimeraFsException, IOException {
+
+        FsInode inode = mock(FsInode.class);
+        Stat stat = mock(Stat.class);
+
+        given(stat.getNlink()).willReturn(-7);
+        given(inode.stat()).willReturn(stat);
+        given(inode.statCache()).willReturn(stat);
+        given(inode.newDirectoryStream()).willReturn( new DirectoryStreamB<HimeraDirectoryEntry>() {
+
+            @Override
+            public Iterator<HimeraDirectoryEntry> iterator() {
+                return Collections.emptyIterator();
+            }
+
+            @Override
+            public void close() throws IOException {}
+        });
+        DirectoryStreamHelper.listOf(inode);
+    }
+
+}