### Question:
AccessTokenValidator { protected static String extractAccessToken(String header) { Matcher m = AUTH_BEARER_PATTERN.matcher(header); if (m.find()) { return m.group(2); } return null; }    }### Answer:
@Test public void when_header_extract_access_token() throws Exception { String header = "Bearer ab1f63c52d1bb435f1d9c97c805b6a04d62cbbad7f1876038cd9f5362c37ac5a1"; String accessToken = AccessTokenValidator.extractAccessToken(header); assertEquals(accessToken, "ab1f63c52d1bb435f1d9c97c805b6a04d62cbbad7f1876038cd9f5362c37ac5a1"); }