### Question:
RequestProviderService { public String getOAuth2Token() { String headerValue = getHeader(HttpHeaders.AUTHORIZATION); return StringUtils.isEmpty(headerValue) ? null : headerValue.replace("Bearer ", ""); }  Optional<Boolean> resolveTppRedirectPreferred(); RequestData getRequestData(); PsuIdData getPsuIdData(); @NotNull UUID getInternalRequestId(); @Nullable String getInstanceId(); String getInternalRequestIdString(); UUID getRequestId(); String getRequestIdString(); boolean isRequestFromPsu(); boolean isRequestFromTPP(); String getPsuIpAddress(); String getTppRedirectURI(); String getTppNokRedirectURI(); String getOAuth2Token(); String getTppRolesAllowedHeader(); @NotNull String getAcceptHeader(); String getContentTypeHeader(); String getEncodedTppQwacCert(); String getTppBrandLoggingInformationHeader(); Boolean getTppRejectionNoFundsPreferred();  }### Answer:
@Test void getOAuth2Token() { when(httpServletRequest.getHeader(HttpHeaders.AUTHORIZATION)).thenReturn(TOKEN); String actualAuthorisationHeader = requestProviderService.getOAuth2Token(); assertEquals(TOKEN, actualAuthorisationHeader); }