### Question:
AS2HttpHelper { @Nullable public static String getCleanContentType (@Nullable final String sContentType) { final ContentType aCT = parseContentType (sContentType); return aCT != null ? aCT.toString () : null; } private  AS2HttpHelper(); @Nullable static ContentType parseContentType(@Nullable final String sContentType); @Nullable static String getCleanContentType(@Nullable final String sContentType); @Nonnull static InternetHeaders getAsInternetHeaders(@Nonnull final HttpHeaderMap aHeaders);  }### Answer:
@Test public void testGetCleanContentType () { assertNull (AS2HttpHelper.getCleanContentType (null)); assertNull (AS2HttpHelper.getCleanContentType ("")); assertNull (AS2HttpHelper.getCleanContentType (" ")); assertNull (AS2HttpHelper.getCleanContentType ("abc")); assertNull (AS2HttpHelper.getCleanContentType ("abc/")); assertEquals ("abc/def", AS2HttpHelper.getCleanContentType ("abc/def")); assertEquals ("abc/def; a=b", AS2HttpHelper.getCleanContentType ("abc/def; a=b")); assertEquals ("abc/def; a=b", AS2HttpHelper.getCleanContentType (" abc/def ; a = b ")); assertEquals ("abc/def; a=b; c=d", AS2HttpHelper.getCleanContentType ("abc/def; a=b; c=d")); assertEquals ("abc/def; a=b; c=d", AS2HttpHelper.getCleanContentType (" abc/def ; a = b ; c = d ")); }