### Question:
CSSDataURLHelper { public static boolean isDataURL (@Nullable final String sURL) { if (sURL == null) return false; final String sRealURL = sURL.trim (); if (sRealURL.length () < PREFIX_DATA_URL.length ()) return false; return sRealURL.substring (0, PREFIX_DATA_URL.length ()).toLowerCase (Locale.US).equals (PREFIX_DATA_URL); } private  CSSDataURLHelper(); static boolean isDataURL(@Nullable final String sURL); @Nullable static CSSDataURL parseDataURL(@Nullable final String sDataURL); static final Charset DEFAULT_CHARSET; static final IMimeType DEFAULT_MIME_TYPE; static final String PREFIX_DATA_URL; static final String BASE64_MARKER; static final char SEPARATOR_CONTENT; static final EMimeQuoting MIME_QUOTING; }### Answer:
@Test public void testIsDataURL () { assertFalse (CSSDataURLHelper.isDataURL (null)); assertFalse (CSSDataURLHelper.isDataURL ("")); assertFalse (CSSDataURLHelper.isDataURL ("data")); assertFalse (CSSDataURLHelper.isDataURL (" data")); assertTrue (CSSDataURLHelper.isDataURL ("data:")); assertTrue (CSSDataURLHelper.isDataURL (" data:")); assertTrue (CSSDataURLHelper.isDataURL (" data: ")); assertTrue (CSSDataURLHelper.isDataURL (" data:,")); assertTrue (CSSDataURLHelper.isDataURL ("data:any")); assertTrue (CSSDataURLHelper.isDataURL (" data:any")); assertTrue (CSSDataURLHelper.isDataURL ("daTA:")); assertTrue (CSSDataURLHelper.isDataURL (" daTA:")); assertTrue (CSSDataURLHelper.isDataURL (" daTA: ")); assertTrue (CSSDataURLHelper.isDataURL (" daTA:,")); assertTrue (CSSDataURLHelper.isDataURL ("daTA:any")); assertTrue (CSSDataURLHelper.isDataURL (" daTA:any")); for (final String sValid : VALID_PLAIN) assertTrue (CSSDataURLHelper.isDataURL (sValid)); for (final String sValid : VALID_BASE64) assertTrue (CSSDataURLHelper.isDataURL (sValid)); }