improve test

Author: martijnvg

server/src/test/java/org/elasticsearch/index/store/FsDirectoryFactoryTests.java

@@ -70,6 +70,9 @@ public void testPreload() throws IOException {
             assertFalse(FsDirectoryFactory.HybridDirectory.useDelegate("foo.kdi", Store.READONCE_CHECKSUM));
             assertTrue(FsDirectoryFactory.HybridDirectory.useDelegate("foo.tmp", newIOContext(random())));
             assertFalse(FsDirectoryFactory.HybridDirectory.useDelegate("foo.fdt__0.tmp", newIOContext(random())));
+            assertFalse(FsDirectoryFactory.HybridDirectory.useDelegate("_0.fdt__1.tmp", newIOContext(random())));
+            assertTrue(FsDirectoryFactory.HybridDirectory.useDelegate("_0.fdm__0.tmp", newIOContext(random())));
+            assertTrue(FsDirectoryFactory.HybridDirectory.useDelegate("_0.fdx__4.tmp", newIOContext(random())));
             MMapDirectory delegate = hybridDirectory.getDelegate();
             assertThat(delegate, Matchers.instanceOf(MMapDirectory.class));
             var func = fsDirectoryFactory.preLoadFuncMap.get(delegate);