### Question:
OAuth1Template implements OAuth1Operations { public void setRequestFactory(ClientHttpRequestFactory requestFactory) { Assert.notNull(requestFactory, "The requestFactory property cannot be null"); restTemplate.setRequestFactory(requestFactory); } OAuth1Template(String consumerKey, String consumerSecret, String requestTokenUrl, String authorizeUrl, String accessTokenUrl);  OAuth1Template(String consumerKey, String consumerSecret, String requestTokenUrl, String authorizeUrl, String accessTokenUrl, OAuth1Version version);  OAuth1Template(String consumerKey, String consumerSecret, String requestTokenUrl, String authorizeUrl, String authenticateUrl, String accessTokenUrl);  OAuth1Template(String consumerKey, String consumerSecret, String requestTokenUrl, String authorizeUrl, String authenticateUrl, String accessTokenUrl, OAuth1Version version); void setRequestFactory(ClientHttpRequestFactory requestFactory); OAuth1Version getVersion(); OAuthToken fetchRequestToken(String callbackUrl, MultiValueMap<String, String> additionalParameters); String buildAuthorizeUrl(String requestToken, OAuth1Parameters parameters); String buildAuthenticateUrl(String requestToken, OAuth1Parameters parameters); OAuthToken exchangeForAccessToken(AuthorizedRequestToken requestToken, MultiValueMap<String, String> additionalParameters);  }### Answer:
@Test(expected = IllegalArgumentException.class) public void setRequestFactory_null() { oauth10a.setRequestFactory(null); }