Index: lucene/src/test/org/apache/lucene/util/automaton/fst/TestFSTs.java
===================================================================
--- lucene/src/test/org/apache/lucene/util/automaton/fst/TestFSTs.java	(revision 1095068)
+++ lucene/src/test/org/apache/lucene/util/automaton/fst/TestFSTs.java	(working copy)
@@ -941,16 +941,15 @@
     }
 
     final LineFileDocs docs = new LineFileDocs(random);
-    final int RUN_TIME_SEC = LuceneTestCase.TEST_NIGHTLY ? 100 : 1;
     final IndexWriterConfig conf = newIndexWriterConfig(TEST_VERSION_CURRENT, new MockAnalyzer(random)).setMaxBufferedDocs(-1).setRAMBufferSizeMB(64);
     final File tempDir = _TestUtil.getTempDir("fstlines");
-    final MockDirectoryWrapper dir = new MockDirectoryWrapper(random, FSDirectory.open(tempDir));
+    final MockDirectoryWrapper dir = newFSDirectory(tempDir);
     final IndexWriter writer = new IndexWriter(dir, conf);
     writer.setInfoStream(VERBOSE ? System.out : null);
-    final long stopTime = System.currentTimeMillis() + RUN_TIME_SEC * 1000;
+    final long stopDocs = LuceneTestCase.TEST_NIGHTLY ? _TestUtil.nextInt(random, 100000, 500000) : _TestUtil.nextInt(random, 1000, 5000);
     Document doc;
     int docCount = 0;
-    while((doc = docs.nextDoc()) != null && System.currentTimeMillis() < stopTime) {
+    while((doc = docs.nextDoc()) != null && docCount < stopDocs) {
       writer.addDocument(doc);
       docCount++;
     }