### Question:
FilePathBuilder { public FilePathBuilder append(final String path) { if (path == null || path.isEmpty()) { return this; } this.path.append(File.separator); insert(path); return this; } FilePathBuilder(final String path); FilePathBuilder append(final String path); @Override String toString();  }### Answer:
@Test public void testAppend() throws Exception { String path1 = "org", path2 = "bonita", path3 = "web/service"; FilePathBuilder path = new FilePathBuilder(path1).append(path2).append(path3); assertEquals(buildExpectedPath(path1, path2, path3), path.toString()); }