adding test for HostQueue crawl stack

- simulating problem with zero length stack file (but not fixing it)
- adding test data clean to maven pom

pom.xml

@@ -99,6 +99,18 @@
                 </configuration>
             </plugin>
 
+            <plugin>
+                <artifactId>maven-clean-plugin</artifactId>
+                <version>2.5</version>
+                <configuration>
+                    <filesets>
+                        <fileset>
+                            <directory>test/DATA</directory>
+                        </fileset>
+                    </filesets>
+                </configuration>
+            </plugin>
+            
             <plugin>
                 <artifactId>maven-assembly-plugin</artifactId>
                 <version>2.4</version>

test/net/yacy/crawler/HostQueueTest.java

@@ -0,0 +1,62 @@
+
+package net.yacy.crawler;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.MalformedURLException;
+import net.yacy.cora.document.id.DigestURL;
+import net.yacy.cora.util.SpaceExceededException;
+import net.yacy.crawler.retrieval.Request;
+import static org.junit.Assert.*;
+import org.junit.Test;
+
+/**
+* test HostQueue
+* directorylayout is
+*
+*   stackDir                      (dir)
+*      +-- hostDir                (dir)
+*           +-- crawldepth.stack  (file)
+*/
+public class HostQueueTest {
+    final String stackDir = "test/DATA/INDEX/QUEUE/CrawlerCoreStacks";
+
+    /**
+     * Test of clear method, of class HostQueue.
+     */
+    @Test
+    public void testClear() throws MalformedURLException, IOException, SpaceExceededException {
+        File stackDirFile = new File(stackDir);
+        String hostDir = "a.com";
+        int hostPort = 80;
+
+        // open queue
+        HostQueue testhq = new HostQueue(stackDirFile, hostDir, hostPort, true, true);
+
+        // add a url
+        String urlstr = "http://" + hostDir + "/test.html";
+        DigestURL url = new DigestURL(urlstr);
+        Request req = new Request(url, null);
+        testhq.push(req, null, null);
+
+        int sizeA = testhq.size();
+        assertTrue (sizeA > 0);
+
+        testhq.clear(); // clear the complete host queue (should delete all files in stackDir)
+
+        int sizeB = testhq.size();
+        assertEquals (0,sizeB);
+
+        // verify stackDir empty (double check)
+        String[] filelist = stackDirFile.list();
+        assertEquals ("host files in queue dir",0,filelist.length);
+
+        testhq.close();
+
+        // verify stackDir empty
+        filelist = stackDirFile.list();
+        assertEquals ("host files in queue dir",0,filelist.length);
+
+    }
+
+}