prepare a IndexSegment test case for RWI index testing

+ prevent NPE in Segment.clear() on missing embedded solr instance.

source/net/yacy/search/index/Fulltext.java

@@ -226,8 +226,8 @@ public final class Fulltext {
                 for (String name: instance.getCoreNames()) {
                     this.solrInstances.getEmbeddedConnector(name).clear();
                 }
+                this.commit(false);
             }
-            this.commit(false);
             this.solrInstances.clearCaches();
         }
     }

test/java/net/yacy/search/index/SegmentTest.java

@@ -0,0 +1,79 @@
+package net.yacy.search.index;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.MalformedURLException;
+import net.yacy.cora.document.encoding.UTF8;
+import net.yacy.cora.document.id.DigestURL;
+import net.yacy.cora.document.id.MultiProtocolURL;
+import net.yacy.cora.util.ConcurrentLog;
+import net.yacy.cora.util.SpaceExceededException;
+import net.yacy.crawler.retrieval.Response;
+import net.yacy.kelondro.data.word.Word;
+import net.yacy.kelondro.data.word.WordReferenceRow;
+import net.yacy.kelondro.util.Bitfield;
+import org.junit.AfterClass;
+import static org.junit.Assert.assertTrue;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class SegmentTest {
+
+    static Segment index;
+
+    /**
+     * Setup RWI index
+     * @throws IOException
+     */
+    @BeforeClass
+    public static void setUpClass() throws IOException {
+        // setup a index segment
+        index = new Segment(new ConcurrentLog("SegmentTest"),
+                new File("test/DATA/INDEX/webportal/SEGMENTS"),
+                new File("test/DATA/INDEX/webportal/ARCHIVE"),
+                null, null);
+
+        // connect RWI index
+        index.connectRWI(10, 1024);
+    }
+
+    @AfterClass
+    public static void tearDownClass() {
+        index.close();
+        ConcurrentLog.shutdown();
+    }
+
+    /**
+     * Test of clear method (for RWI), of class Segment.
+     */
+    @Test
+    public void testClear() throws MalformedURLException, IOException, SpaceExceededException {
+        DigestURL url = new DigestURL("http://test.org/test.html");
+        int urlComps = MultiProtocolURL.urlComps(url.toNormalform(true)).length;
+        int urlLength = url.toNormalform(true).length();
+
+        byte[] termHash = Word.word2hash("test");
+        Word word = new Word(1, 1, 1);
+        word.flags = new Bitfield(4); // flags must not be null
+
+        WordReferenceRow ientry = new WordReferenceRow(
+                url.hash(), urlLength, urlComps, 0, 1, 1,
+                System.currentTimeMillis(), System.currentTimeMillis(),
+                UTF8.getBytes("en"), Response.DT_TEXT, 0, 0);
+        ientry.setWord(word);
+
+        // add a dummy Word and WordReference
+        index.termIndex.add(termHash, ientry);
+
+        // check index count
+        long cnt = index.RWICount();
+        assertTrue(cnt > 0);
+
+        index.clear();
+
+        // check index count after clear
+        cnt = index.RWICount();
+        assertTrue(cnt == 0);
+    }
+
+}