public static String appendPathSeparatorIfMissing(String path) {
        return StringUtils.appendIfMissing(path, "/", "/");
    }
@Test
    void appendPathSeparatorIfMissing() {
        String s = PathUtils.appendPathSeparatorIfMissing("a");
        assertThat(s).isEqualTo("a/");

        s = PathUtils.appendPathSeparatorIfMissing("a/");
        assertThat(s).isEqualTo("a/");

        s = PathUtils.appendPathSeparatorIfMissing(null);
        assertThat(s).isEqualTo(null);
    }