### Question:
ImportFileUtils { public Collection<File> listImportFiles(String importDir) { Preconditions.checkState(importDir != null); return FileUtils.listFiles(new File(StringUtils.appendIfMissing(importDir, "/")), eligibleFileExtensions, true); }  Collection<File> listImportFiles(String importDir); Reader getReader(File file); void setEligibleFileExtensions(String[] eligibleFileExtensions); void setFileCharset(String fileCharset);  }### Answer:
@Test public void listImportFiles() { importFileUtils.setEligibleFileExtensions(new String[]{"json.gz", "json"}); Collection<File> files = importFileUtils.listImportFiles(importDir.getAbsolutePath()); assertEquals(2, files.size()); assertTrue(files.contains(importFileJsonGz)); assertTrue(files.contains(importFileJson)); }