LUCENE-5433: test of BooleanQuery.rewrite's single clause optimization

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1594330 13f79535-47bb-0310-9956-ffa450edef68

lucene/core/src/test/org/apache/lucene/search/TestBooleanQuery.java

@@ -352,4 +352,42 @@ public class TestBooleanQuery extends LuceneTestCase {
     dir.close();
   }
 
+  public void testOneClauseRewriteOptimization() throws Exception {
+    final float BOOST = 3.5F;
+    final String FIELD = "content";
+    final String VALUE = "foo";
+      
+    Directory dir = newDirectory();
+    (new RandomIndexWriter(random(), dir)).shutdown();
+    IndexReader r = DirectoryReader.open(dir);
+
+    TermQuery expected = new TermQuery(new Term(FIELD, VALUE));
+    expected.setBoost(BOOST);
+
+    final int numLayers = atLeast(3);
+    boolean needBoost = true;
+    Query actual = new TermQuery(new Term(FIELD, VALUE));
+
+    for (int i = 0; i < numLayers; i++) {
+      if (needBoost && 0 == TestUtil.nextInt(random(),0,numLayers)) {
+        needBoost = false;
+        actual.setBoost(BOOST);
+      }
+
+      BooleanQuery bq = new BooleanQuery();
+      bq.add(actual, random().nextBoolean() 
+             ? BooleanClause.Occur.SHOULD : BooleanClause.Occur.MUST);
+      actual = bq;
+    }
+    if (needBoost) {
+      actual.setBoost(BOOST);
+    }
+
+    assertEquals(numLayers + ": " + actual.toString(),
+                 expected, actual.rewrite(r));
+
+    r.close();
+    dir.close();
+  }
+
 }