### Question:
OAuth2Template implements OAuth2Operations { public AccessGrant authenticateClient() { return authenticateClient(null); } OAuth2Template(String clientId, String clientSecret, String authorizeUrl, String accessTokenUrl);  OAuth2Template(String clientId, String clientSecret, String authorizeUrl, String authenticateUrl, String accessTokenUrl); void setUseParametersForClientAuthentication(boolean useParametersForClientAuthentication); void setRequestFactory(ClientHttpRequestFactory requestFactory); String buildAuthorizeUrl(OAuth2Parameters parameters); String buildAuthorizeUrl(GrantType grantType, OAuth2Parameters parameters); String buildAuthenticateUrl(OAuth2Parameters parameters); String buildAuthenticateUrl(GrantType grantType, OAuth2Parameters parameters); AccessGrant exchangeForAccess(String authorizationCode, String redirectUri, MultiValueMap<String, String> additionalParameters); AccessGrant exchangeCredentialsForAccess(String username, String password, MultiValueMap<String, String> additionalParameters); @Deprecated AccessGrant refreshAccess(String refreshToken, String scope, MultiValueMap<String, String> additionalParameters); AccessGrant refreshAccess(String refreshToken, MultiValueMap<String, String> additionalParameters); AccessGrant authenticateClient(); AccessGrant authenticateClient(String scope);  }### Answer:
@Test public void authenticateClient() { AccessGrant accessGrant = clientCredentials("accessToken_noUser.json"); assertEquals("8d0a88a5c4f1ae4937ad864cafa8e857", accessGrant.getAccessToken()); long approximateExpirationTime = System.currentTimeMillis() + 40735000; long actualExpirationTime = (long) accessGrant.getExpireTime(); assertTrue(approximateExpirationTime - actualExpirationTime < 1000); assertEquals("read,write", accessGrant.getScope()); }