### Question:
OpenIDConnectClientImpl implements OpenIDConnectClient { public TokenSet refreshTokens(String refreshToken) { if (log.isInfoEnabled()) log.info("Refreshing tokens for client "+clientId); if (log.isDebugEnabled()) log.debug("Using refresh token " + refreshToken); if (refreshToken == null || refreshToken.trim().isEmpty()) throw new IllegalArgumentException("refreshToken must not be null or empty"); refreshToken = refreshToken.trim(); List<NameValuePair> params = new ArrayList<NameValuePair>(); params.add(new BasicNameValuePair("grant_type", "refresh_token")); params.add(new BasicNameValuePair("client_id", clientId)); params.add(new BasicNameValuePair("refresh_token", refreshToken)); return getTokenSetInner(params); } OpenIDConnectClientImpl(
			final String authorizeUrl,
			final String tokenUrl,
			final String clientId,
			final String clientSecret,
			final LoginFormAdapter loginFormAdapter); @Override URI getAuthorizeURI(String redirectUri); @Override URI getAuthorizeURI(String redirectUri, String scope); @Override String authorize(String username, String password, String redirectUri); @Override String authorize(String username, String password, String redirectUri, String scope); TokenSet getTokens(String authCode, String redirectUri); TokenSet refreshTokens(String refreshToken); static final String DEFAULT_SCOPE; }### Answer:
@Test public void testRefreshTokensNullToken() { thrown.expect(IllegalArgumentException.class); client.refreshTokens(null); }
@Test public void testRefreshTokensEmptyToken() { thrown.expect(IllegalArgumentException.class); client.refreshTokens(" "); }