### Question:
OAuth2Template implements OAuth2Operations { public void setRequestFactory(ClientHttpRequestFactory requestFactory) { Assert.notNull(requestFactory, "The requestFactory property cannot be null"); getRestTemplate().setRequestFactory(requestFactory); } 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(expected = IllegalArgumentException.class) public void setRequestFactory_null() { oAuth2Template.setRequestFactory(null); }