implement instances via one base URL per instance

Previously, instances were addressed in various ways depending on then
request (GET parameter, some instance_id in the POST body).  With this
commit, users of the merchant backend don't see the instance, they just
see another base URL.

18 files changed, 115 insertions, 226 deletions

diff --git a/src/lib/merchant_api_check_payment.c b/src/lib/merchant_api_check_payment.c
index 8c057072..8848686d 100644
--- a/src/lib/merchant_api_check_payment.c
+++ b/src/lib/merchant_api_check_payment.c
@@ -174,7 +174,6 @@ handle_check_payment_finished (void *cls,
  *
  * @param ctx execution context
  * @param backend_url base URL of the merchant backend
- * @param instance instance used for the transaction
  * @param order_id order id to identify the payment
  * @parem session_id sesion id for the payment (or NULL if the payment is not bound to a session) 
  * @param check_payment_cb callback which will work the response gotten from the backend
@@ -184,7 +183,6 @@ handle_check_payment_finished (void *cls,
 struct TALER_MERCHANT_CheckPaymentOperation *
 TALER_MERCHANT_check_payment (struct GNUNET_CURL_Context *ctx,
                               const char *backend_url,
-                              const char *instance,
                               const char *order_id,
                               const char *session_id,
                               TALER_MERCHANT_CheckPaymentCallback check_payment_cb,
@@ -194,15 +192,13 @@ TALER_MERCHANT_check_payment (struct GNUNET_CURL_Context *ctx,
   CURL *eh;
 
   GNUNET_assert (NULL != backend_url);
-  GNUNET_assert (NULL != instance);
   GNUNET_assert (NULL != order_id);
 
   cpo = GNUNET_new (struct TALER_MERCHANT_CheckPaymentOperation);
   cpo->ctx = ctx;
   cpo->cb = check_payment_cb;
   cpo->cb_cls = check_payment_cb_cls;
-  cpo->url = TALER_url_join (backend_url, "/check-payment",
-                             "instance", instance,
+  cpo->url = TALER_url_join (backend_url, "check-payment",
                              "order_id", order_id,
                              "session_id", session_id,
                              NULL);
diff --git a/src/lib/merchant_api_history.c b/src/lib/merchant_api_history.c
index bab8d82a..d1cbfcfa 100644
--- a/src/lib/merchant_api_history.c
+++ b/src/lib/merchant_api_history.c
@@ -153,7 +153,6 @@ history_raw_cb (void *cls,
  *
  * @param ctx execution context
  * @param backend_url base URL of the merchant backend
- * @param instance which merchant instance is performing this call
  * @param start return `delta` records starting from position `start`.
  *        If given as zero, then no initial skip of `start` records is done.
  * @param use_default_start do NOT include the 'start' argument in URL.
@@ -166,7 +165,6 @@ history_raw_cb (void *cls,
 static struct TALER_MERCHANT_HistoryOperation *
 TALER_MERCHANT_history2 (struct GNUNET_CURL_Context *ctx,
                          const char *backend_url,
-                         const char *instance,
                          unsigned long long start,
                          int use_default_start,
                          long long delta,
@@ -184,21 +182,19 @@ TALER_MERCHANT_history2 (struct GNUNET_CURL_Context *ctx,
   ho->cb = history_cb;
   ho->cb_cls = history_cb_cls;
   seconds = date.abs_value_us / 1000LL / 1000LL;
-  base = TALER_url_join (backend_url, "/history", NULL);
+  base = TALER_url_join (backend_url, "history", NULL);
 
   if (GNUNET_YES == use_default_start)
     GNUNET_asprintf (&ho->url,
-                     "%s?date=%llu&instance=%s&delta=%lld",
+                     "%s?date=%llu&delta=%lld",
                      base,
                      seconds,
-                     instance,
                      delta);
   else
     GNUNET_asprintf (&ho->url,
-                     "%s?date=%llu&instance=%s&delta=%lld&start=%llu",
+                     "%s?date=%llu&delta=%lld&start=%llu",
                      base,
                      seconds,
-                     instance,
                      delta,
                      start);
     
@@ -232,7 +228,6 @@ TALER_MERCHANT_history2 (struct GNUNET_CURL_Context *ctx,
  *
  * @param ctx execution context
  * @param backend_url base URL of the merchant backend
- * @param instance which merchant instance is performing this call
  * @param start return `delta` records starting from position
  *        `start`.  If given as zero, then no initial skip of
  *        `start` records is done.
@@ -249,7 +244,6 @@ struct TALER_MERCHANT_HistoryOperation *
 TALER_MERCHANT_history_default_start
   (struct GNUNET_CURL_Context *ctx,
    const char *backend_url,
-   const char *instance,
    long long delta,
    struct GNUNET_TIME_Absolute date,
    TALER_MERCHANT_HistoryOperationCallback history_cb,
@@ -257,7 +251,6 @@ TALER_MERCHANT_history_default_start
 {
   return TALER_MERCHANT_history2 (ctx,
                                   backend_url,
-                                  instance,
                 /* fake 'start' argument: will NOT be used */
                                   -1, 
                 /* Specifies "no start argument" in final URL */
@@ -274,7 +267,6 @@ TALER_MERCHANT_history_default_start
  *
  * @param ctx execution context
  * @param backend_url base URL of the merchant backend
- * @param instance which merchant instance is performing this call
  * @param start return `delta` records starting from position
  *        `start`.  If given as zero, then no initial skip of
  *        `start` records is done.
@@ -291,7 +283,6 @@ struct TALER_MERCHANT_HistoryOperation *
 TALER_MERCHANT_history
   (struct GNUNET_CURL_Context *ctx,
    const char *backend_url,
-   const char *instance,
    unsigned long long start,
    long long delta,
    struct GNUNET_TIME_Absolute date,
@@ -300,7 +291,6 @@ TALER_MERCHANT_history
 {
   return TALER_MERCHANT_history2 (ctx,
                                   backend_url,
-                                  instance,
                                   start,
                                   GNUNET_NO,
                                   delta,
diff --git a/src/lib/merchant_api_pay.c b/src/lib/merchant_api_pay.c
index 0505e950..c7919a04 100644
--- a/src/lib/merchant_api_pay.c
+++ b/src/lib/merchant_api_pay.c
@@ -598,7 +598,7 @@ request_pay_generic
   ph->abort_cb_cls = abort_cb_cls;
   ph->pay_cb = pay_cb;
   ph->pay_cb_cls = pay_cb_cls;
-  ph->url = TALER_url_join (merchant_url, "/public/pay", NULL);
+  ph->url = TALER_url_join (merchant_url, "public/pay", NULL);
   ph->num_coins = num_coins;
   ph->coins = GNUNET_new_array (num_coins,
                                 struct TALER_MERCHANT_PaidCoin);
@@ -639,8 +639,6 @@ request_pay_generic
  *
  * @param ctx the execution loop context
  * @param merchant_url base URL of the merchant's backend
- * @param instance which merchant instance will receive this
- *        payment
  * @param h_contract_terms hashcode of the proposal being paid
  * @param amount total value of the contract to be paid to the
  *        merchant
@@ -668,7 +666,6 @@ request_pay_generic
 static struct TALER_MERCHANT_Pay *
 prepare_pay_generic (struct GNUNET_CURL_Context *ctx,
                      const char *merchant_url,
-                     const char *instance,
                      const struct GNUNET_HashCode *h_contract_terms,
                      const struct TALER_Amount *amount,
                      const struct TALER_Amount *max_fee,
@@ -774,7 +771,6 @@ prepare_pay_generic (struct GNUNET_CURL_Context *ctx,
  *
  * @param ctx the execution loop context
  * @param merchant_url base URL of the merchant's backend
- * @param instance which merchant instance will receive this payment
  * @param h_contract_terms hashcode of the proposal being paid
  * @param amount total value of the contract to be paid to the merchant
  * @param max_fee maximum fee covered by the merchant (according to the contract)
@@ -794,7 +790,6 @@ prepare_pay_generic (struct GNUNET_CURL_Context *ctx,
 struct TALER_MERCHANT_Pay *
 TALER_MERCHANT_pay_wallet (struct GNUNET_CURL_Context *ctx,
                            const char *merchant_url,
-                           const char *instance,
                            const struct GNUNET_HashCode *h_contract_terms,
                            const struct TALER_Amount *amount,
                            const struct TALER_Amount *max_fee,
@@ -812,7 +807,6 @@ TALER_MERCHANT_pay_wallet (struct GNUNET_CURL_Context *ctx,
 {
   return prepare_pay_generic (ctx,
                               merchant_url,
-                              instance,
                               h_contract_terms,
                               amount,
                               max_fee,
@@ -839,7 +833,6 @@ TALER_MERCHANT_pay_wallet (struct GNUNET_CURL_Context *ctx,
  *
  * @param ctx execution context
  * @param merchant_url base URL of the merchant
- * @param instance which merchant instance will receive this payment
  * @param h_wire hash of the merchant’s account details
  * @param h_contract hash of the contact of the merchant with the customer
  * @param transaction_id transaction id for the transaction between merchant and customer
@@ -860,7 +853,6 @@ TALER_MERCHANT_pay_wallet (struct GNUNET_CURL_Context *ctx,
 struct TALER_MERCHANT_Pay *
 TALER_MERCHANT_pay_abort (struct GNUNET_CURL_Context *ctx,
                           const char *merchant_url,
-                          const char *instance,
                           const struct GNUNET_HashCode *h_contract,
                           const struct TALER_Amount *amount,
                           const struct TALER_Amount *max_fee,
@@ -880,7 +872,6 @@ TALER_MERCHANT_pay_abort (struct GNUNET_CURL_Context *ctx,
 
   ph = prepare_pay_generic (ctx,
                             merchant_url,
-                            instance,
                             h_contract,
                             amount,
                             max_fee,
diff --git a/src/lib/merchant_api_proposal.c b/src/lib/merchant_api_proposal.c
index 25552bc0..83371eda 100644
--- a/src/lib/merchant_api_proposal.c
+++ b/src/lib/merchant_api_proposal.c
@@ -229,7 +229,7 @@ TALER_MERCHANT_order_put
   po->ctx = ctx;
   po->cb = proposal_cb;
   po->cb_cls = proposal_cb_cls;
-  po->url = TALER_url_join (backend_url, "/order", NULL);
+  po->url = TALER_url_join (backend_url, "order", NULL);
   req = json_pack ("{s:O}",
                    "order", (json_t *) order);
   eh = curl_easy_init ();
@@ -366,7 +366,6 @@ struct TALER_MERCHANT_ProposalLookupOperation *
 TALER_MERCHANT_proposal_lookup (struct GNUNET_CURL_Context *ctx,
                                 const char *backend_url,
                                 const char *order_id,
-                                const char *instance,
                                 const struct
                                 GNUNET_CRYPTO_EddsaPublicKey *nonce,
                                 TALER_MERCHANT_ProposalLookupOperationCallback
@@ -375,38 +374,25 @@ TALER_MERCHANT_proposal_lookup (struct GNUNET_CURL_Context *ctx,
 {
   struct TALER_MERCHANT_ProposalLookupOperation *plo;
   CURL *eh;
-  char *base;
+  char *nonce_str = NULL;
 
   plo = GNUNET_new (struct TALER_MERCHANT_ProposalLookupOperation);
   plo->ctx = ctx;
   plo->cb = plo_cb;
   plo->cb_cls = plo_cb_cls;
-  base = TALER_url_join (backend_url, "/public/proposal", NULL);
   if (NULL != nonce)
   {
-    char *nonce_str;
     plo->has_nonce = GNUNET_YES;
     plo->nonce = *nonce;
     nonce_str = GNUNET_STRINGS_data_to_string_alloc (nonce, sizeof (struct
                                                                     GNUNET_CRYPTO_EddsaPublicKey));
-    GNUNET_assert (NULL != nonce_str);
-    GNUNET_asprintf (&plo->url,
-                     "%s?order_id=%s&instance=%s&nonce=%s",
-                     base,
-                     order_id,
-                     instance,
-                     nonce_str);
-    GNUNET_free (nonce_str);
   }
-  else
-  {
-    GNUNET_asprintf (&plo->url,
-                     "%s?order_id=%s&instance=%s",
-                     base,
-                     order_id,
-                     instance);
-  }
-  GNUNET_free (base);
+  plo->url = TALER_url_join (backend_url, "public/proposal",
+                             "order_id",
+                             order_id,
+                             "nonce",
+                             nonce_str,
+                             NULL);
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "looking up proposal from %s\n",
               plo->url);
diff --git a/src/lib/merchant_api_refund.c b/src/lib/merchant_api_refund.c
index 76a01e5d..3f888099 100644
--- a/src/lib/merchant_api_refund.c
+++ b/src/lib/merchant_api_refund.c
@@ -190,7 +190,6 @@ TALER_MERCHANT_refund_increase_cancel (struct TALER_MERCHANT_RefundIncreaseOpera
  * @param order_id id of the order whose refund is to be increased
  * @param refund amount to which increase the refund
  * @param reason human-readable reason justifying the refund
- * @param instance id of the merchant instance issuing the request
  * @param cb callback processing the response from /refund
  * @param cb_cls closure for cb
  */
@@ -200,7 +199,6 @@ TALER_MERCHANT_refund_increase (struct GNUNET_CURL_Context *ctx,
                                 const char *order_id,
                                 const struct TALER_Amount *refund,
                                 const char *reason,
-                                const char *instance,
                                 TALER_MERCHANT_RefundIncreaseCallback cb,
                                 void *cb_cls)
 {
@@ -212,12 +210,11 @@ TALER_MERCHANT_refund_increase (struct GNUNET_CURL_Context *ctx,
   rio->ctx = ctx;
   rio->cb = cb;
   rio->cb_cls = cb_cls;
-  rio->url = TALER_url_join (backend_url, "/refund", NULL);
-  req = json_pack ("{s:o, s:s, s:s, s:s}",
+  rio->url = TALER_url_join (backend_url, "refund", NULL);
+  req = json_pack ("{s:o, s:s, s:s}",
                    "refund", TALER_JSON_from_amount (refund),
                    "order_id", order_id,
-                   "reason", reason,
-                   "instance", instance);
+                   "reason", reason);
   eh = curl_easy_init ();
 
   if (GNUNET_OK != TALER_curl_easy_post (&rio->post_ctx,
@@ -333,26 +330,18 @@ struct TALER_MERCHANT_RefundLookupOperation *
 TALER_MERCHANT_refund_lookup (struct GNUNET_CURL_Context *ctx,
                               const char *backend_url,
                               const char *order_id,
-                              const char *instance,
                               TALER_MERCHANT_RefundLookupCallback cb,
                               void *cb_cls)
 {
   struct TALER_MERCHANT_RefundLookupOperation *rlo;
   CURL *eh;
-  char *base;
 
   rlo = GNUNET_new (struct TALER_MERCHANT_RefundLookupOperation);
   rlo->ctx = ctx;
   rlo->cb = cb;
   rlo->cb_cls = cb_cls;
 
-  base = TALER_url_join (backend_url, "/public/refund", NULL);
-  GNUNET_asprintf (&rlo->url,
-                   "%s?instance=%s&order_id=%s",
-                   base,
-                   instance,
-                   order_id);
-  GNUNET_free (base);
+  rlo->url = TALER_url_join (backend_url, "public/refund", "order_id", order_id, NULL);
   eh = curl_easy_init ();
   if (CURLE_OK != curl_easy_setopt (eh,
                                     CURLOPT_URL,
diff --git a/src/lib/merchant_api_tip_authorize.c b/src/lib/merchant_api_tip_authorize.c
index f79064a6..582c9a4e 100644
--- a/src/lib/merchant_api_tip_authorize.c
+++ b/src/lib/merchant_api_tip_authorize.c
@@ -179,7 +179,6 @@ handle_tip_authorize_finished (void *cls,
  * @param pickup_url frontend URL for where the tip can be picked up
  * @param next_url where the browser should proceed after picking up the tip
  * @param amount amount to be handed out as a tip
- * @param instance which backend instance should create the tip (identifies the reserve and exchange)
  * @param justification which justification should be stored (human-readable reason for the tip)
  * @param authorize_cb callback which will work the response gotten from the backend
  * @param authorize_cb_cls closure to pass to @a authorize_cb
@@ -191,7 +190,6 @@ TALER_MERCHANT_tip_authorize (struct GNUNET_CURL_Context *ctx,
                               const char *pickup_url,
                               const char *next_url,
                               const struct TALER_Amount *amount,
-                              const char *instance,
                               const char *justification,
                               TALER_MERCHANT_TipAuthorizeCallback authorize_cb,
                               void *authorize_cb_cls)
@@ -204,16 +202,14 @@ TALER_MERCHANT_tip_authorize (struct GNUNET_CURL_Context *ctx,
   tao->ctx = ctx;
   tao->cb = authorize_cb;
   tao->cb_cls = authorize_cb_cls;
-  tao->url = TALER_url_join (backend_url, "/tip-authorize", NULL);
+  tao->url = TALER_url_join (backend_url, "tip-authorize", NULL);
   te_obj = json_pack ("{"
                       " s:o," /* amount */
-                      " s:s," /* instance */
                       " s:s," /* justification */
                       " s:s," /* pickup_url */
                       " s:s," /* next_url */
                       "}",
                       "amount", TALER_JSON_from_amount (amount),
-                      "instance", instance,
                       "justification", justification,
                       "pickup_url", pickup_url,
                       "next_url", next_url);
diff --git a/src/lib/merchant_api_tip_pickup.c b/src/lib/merchant_api_tip_pickup.c
index e49151bc..116b994c 100644
--- a/src/lib/merchant_api_tip_pickup.c
+++ b/src/lib/merchant_api_tip_pickup.c
@@ -288,7 +288,7 @@ TALER_MERCHANT_tip_pickup (struct GNUNET_CURL_Context *ctx,
   tpo->cb_cls = pickup_cb_cls;
 
   tpo->url = TALER_url_join (backend_url,
-                             "/public/tip-pickup",
+                             "public/tip-pickup",
                              NULL);
   eh = curl_easy_init ();
   if (GNUNET_OK != TALER_curl_easy_post (&tpo->post_ctx,
diff --git a/src/lib/merchant_api_tip_query.c b/src/lib/merchant_api_tip_query.c
index d02de8b1..3887390b 100644
--- a/src/lib/merchant_api_tip_query.c
+++ b/src/lib/merchant_api_tip_query.c
@@ -187,13 +187,11 @@ handle_tip_query_finished (void *cls,
  *
  * @param ctx execution context
  * @param backend_url base URL of the merchant backend
- * @param instance instance to query
  * @return handle for this operation, NULL upon errors
  */
 struct TALER_MERCHANT_TipQueryOperation *
 TALER_MERCHANT_tip_query (struct GNUNET_CURL_Context *ctx,
                           const char *backend_url,
-                          const char *instance,
                           TALER_MERCHANT_TipQueryCallback query_cb,
                           void *query_cb_cls)
 {
@@ -204,8 +202,7 @@ TALER_MERCHANT_tip_query (struct GNUNET_CURL_Context *ctx,
   tqo->ctx = ctx;
   tqo->cb = query_cb;
   tqo->cb_cls = query_cb_cls;
-  tqo->url = TALER_url_join (backend_url, "/tip-query",
-                             "instance", instance,
+  tqo->url = TALER_url_join (backend_url, "tip-query",
                              NULL);
 
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
diff --git a/src/lib/merchant_api_track_transaction.c b/src/lib/merchant_api_track_transaction.c
index 32393ece..e5cac2bb 100644
--- a/src/lib/merchant_api_track_transaction.c
+++ b/src/lib/merchant_api_track_transaction.c
@@ -134,7 +134,6 @@ handle_track_transaction_finished (void *cls,
  *
  * @param ctx execution context
  * @param backend_url base URL of the backend
- * @param instance which merchant instance is going to be tracked
  * @param order_id order id pointing to the transaction being tracked
  * @param track_transaction_cb the callback to call when a reply for this request is available
  * @param track_transaction_cb_cls closure for @a track_transaction_cb
@@ -143,26 +142,19 @@ handle_track_transaction_finished (void *cls,
 struct TALER_MERCHANT_TrackTransactionHandle *
 TALER_MERCHANT_track_transaction (struct GNUNET_CURL_Context *ctx,
                                   const char *backend_url,
-                                  const char *instance,
                                   const char *order_id,
                                   TALER_MERCHANT_TrackTransactionCallback track_transaction_cb,
                                   void *track_transaction_cb_cls)
 {
   struct TALER_MERCHANT_TrackTransactionHandle *tdo;
   CURL *eh;
-  char *base;
 
   tdo = GNUNET_new (struct TALER_MERCHANT_TrackTransactionHandle);
   tdo->ctx = ctx;
   tdo->cb = track_transaction_cb;
   tdo->cb_cls = track_transaction_cb_cls;
-  base = TALER_url_join (backend_url, "/track/transaction", NULL);
-  GNUNET_asprintf (&tdo->url,
-                   "%s?order_id=%s&instance=%s",
-                   base,
-                   order_id,
-                   instance);
-  GNUNET_free (base);
+  tdo->url = TALER_url_join (backend_url, "track/transaction",
+                             "order_id", order_id, NULL);
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "Requesting URL '%s'\n",
               tdo->url);
diff --git a/src/lib/merchant_api_track_transfer.c b/src/lib/merchant_api_track_transfer.c
index b5105c54..df303b1b 100644
--- a/src/lib/merchant_api_track_transfer.c
+++ b/src/lib/merchant_api_track_transfer.c
@@ -219,7 +219,6 @@ handle_track_transfer_finished (void *cls,
  *
  * @param ctx execution context
  * @param backend_url base URL of the backend
- * @param instance which merchant instance is going to be tracked
  * @param wire_method wire method used for the wire transfer
  * @param wtid base32 string indicating a wtid
  * @param exchange_url base URL of the exchange in charge of returning the wanted information
@@ -230,7 +229,6 @@ handle_track_transfer_finished (void *cls,
 struct TALER_MERCHANT_TrackTransferHandle *
 TALER_MERCHANT_track_transfer (struct GNUNET_CURL_Context *ctx,
                                const char *backend_url,
-                               const char *instance,
                                const char *wire_method,
                                const struct
                                TALER_WireTransferIdentifierRawP *wtid,
@@ -250,10 +248,9 @@ TALER_MERCHANT_track_transfer (struct GNUNET_CURL_Context *ctx,
   tdo->ctx = ctx;
   tdo->cb = track_transfer_cb; // very last to be called
   tdo->cb_cls = track_transfer_cb_cls;
-  tdo->url = TALER_url_join (backend_url, "/track/transfer",
+  tdo->url = TALER_url_join (backend_url, "track/transfer",
                              "wtid", wtid_str,
                              "exchange", exchange_url,
-                             "instance", instance,
                              "wire_method", wire_method,
                              NULL);
   GNUNET_free (wtid_str);
diff --git a/src/lib/test_merchant_api.c b/src/lib/test_merchant_api.c
index 67df2b93..fa7a385d 100644
--- a/src/lib/test_merchant_api.c
+++ b/src/lib/test_merchant_api.c
@@ -62,6 +62,26 @@ static char *fakebank_url;
 static char *merchant_url;
 
 /**
+ * Merchant base URL for the tipping instance.
+ */
+static char *merchant_tip_instance_url;
+
+/**
+ * Merchant base URL for the tipping instance.
+ */
+static char *merchant_tip_instance_2_url;
+
+/**
+ * Merchant base URL for the tipping instance.
+ */
+static char *merchant_tip_instance_nulltip_url;
+
+/**
+ * Merchant base URL for a non-existent instance.
+ */
+static char *merchant_tip_unknown_instance_url;
+
+/**
  * Merchant process.
  */
 static struct GNUNET_OS_Process *merchantd;
@@ -212,8 +232,7 @@ run (void *cls,
         \"summary\": \"merchant-lib testcase\",\
         \"fulfillment_url\": \"https://example.com/\",\
         \"products\": [ {\"description\":\"ice cream\",\
-                         \"value\":\"{EUR:5}\"} ] }",
-        NULL),
+                         \"value\":\"{EUR:5}\"} ] }"),
 
     TALER_TESTING_cmd_check_payment ("check-payment-1",
                                      merchant_url,
@@ -287,8 +306,7 @@ run (void *cls,
         \"summary\": \"useful product\",\
         \"fulfillment_url\": \"https://example.com/\",\
         \"products\": [ {\"description\":\"ice cream\",\
-                         \"value\":\"{EUR:5}\"} ] }",
-        NULL),
+                         \"value\":\"{EUR:5}\"} ] }"),
 
     TALER_TESTING_cmd_proposal_lookup ("fetch-proposal-2",
                                        merchant_url,
@@ -485,8 +503,7 @@ run (void *cls,
         \"summary\": \"useful product\",\
         \"fulfillment_url\": \"https://example.com/\",\
         \"products\": [ {\"description\":\"ice cream\",\
-                         \"value\":\"{EUR:5}\"} ] }",
-        NULL),
+                         \"value\":\"{EUR:5}\"} ] }"),
 
     /* Try to increase a non paid proposal.  */
     TALER_TESTING_cmd_refund_increase
@@ -551,8 +568,7 @@ run (void *cls,
         \"summary\": \"merchant-lib testcase\",\
         \"fulfillment_url\": \"https://example.com/\",\
         \"products\": [ {\"description\":\"ice cream\",\
-                         \"value\":\"{EUR:5}\"} ] }",
-        NULL),
+                         \"value\":\"{EUR:5}\"} ] }"),
 
     TALER_TESTING_cmd_pay ("pay-unincreased-proposal",
                            merchant_url,
@@ -613,18 +629,16 @@ run (void *cls,
        "EUR:20.04", USER_ACCOUNT_NO, EXCHANGE_ACCOUNT_NO),
 
     TALER_TESTING_cmd_tip_authorize ("authorize-tip-1",
-                                     merchant_url,
+                                     merchant_tip_instance_url,
                                      exchange_url,
                                      MHD_HTTP_OK,
-                                     "tip",
                                      "tip 1",
                                      "EUR:5.01"),
 
     TALER_TESTING_cmd_tip_authorize ("authorize-tip-2",
-                                     merchant_url,
+                                     merchant_tip_instance_url,
                                      exchange_url,
                                      MHD_HTTP_OK,
-                                     "tip",
                                      "tip 2",
                                      "EUR:5.01"),
 
@@ -635,51 +649,46 @@ run (void *cls,
      * actually create a reserve.  */
     TALER_TESTING_cmd_tip_authorize_with_ec
       ("authorize-tip-null",
-       merchant_url,
+       merchant_tip_instance_nulltip_url,
        exchange_url,
        MHD_HTTP_NOT_FOUND,
-       "nulltip",
        "tip 2",
        "EUR:5.01",
        TALER_EC_RESERVE_STATUS_UNKNOWN),
 
     TALER_TESTING_cmd_tip_query ("query-tip-1",
-                                 merchant_url,
-                                 MHD_HTTP_OK,
-                                 "tip"),
+                                 merchant_tip_instance_url,
+                                 MHD_HTTP_OK),
 
     TALER_TESTING_cmd_tip_query_with_amounts ("query-tip-2",
-                                              merchant_url,
+                                              merchant_tip_instance_url,
                                               MHD_HTTP_OK,
-                                              "tip",
                                               "EUR:0.0", // picked
                                               "EUR:10.02", // auth
                                               "EUR:20.04"),// ava
 
     TALER_TESTING_cmd_tip_pickup ("pickup-tip-1",
-                                  merchant_url,
+                                  merchant_tip_instance_url,
                                   MHD_HTTP_OK,
                                   "authorize-tip-1",
                                   pickup_amounts_1),
 
     TALER_TESTING_cmd_tip_query_with_amounts ("query-tip-3",
-                                              merchant_url,
+                                              merchant_tip_instance_url,
                                               MHD_HTTP_OK,
-                                              "tip",
                                               "EUR:5.01", // picked
                                               NULL, // auth
                                               "EUR:15.03"),// ava
 
     TALER_TESTING_cmd_tip_pickup ("pickup-tip-2",
-                                  merchant_url,
+                                  merchant_tip_instance_url,
                                   MHD_HTTP_OK,
                                   "authorize-tip-2",
                                   pickup_amounts_1),
 
     TALER_TESTING_cmd_tip_query_with_amounts ("query-tip-4",
-                                              merchant_url,
+                                              merchant_tip_instance_url,
                                               MHD_HTTP_OK,
-                                              "tip",
                                               "EUR:10.02", // pick
                                               "EUR:10.02", // auth
                                               "EUR:10.02"), // ava
@@ -708,20 +717,18 @@ run (void *cls,
 
     TALER_TESTING_cmd_tip_authorize_with_ec
       ("authorize-tip-3-insufficient-funds",
-       merchant_url,
+       merchant_tip_instance_2_url,
        exchange_url,
        MHD_HTTP_PRECONDITION_FAILED,
-       "dtip",
        "tip 3",
        "EUR:2.02",
        TALER_EC_TIP_AUTHORIZE_INSUFFICIENT_FUNDS),
 
     TALER_TESTING_cmd_tip_authorize_with_ec
       ("authorize-tip-4-unknown-instance",
-       merchant_url,
+       merchant_tip_unknown_instance_url,
        exchange_url,
        MHD_HTTP_NOT_FOUND,
-       "unknown",
        "tip 4",
        "EUR:5.01",
        TALER_EC_TIP_AUTHORIZE_INSTANCE_UNKNOWN),
@@ -731,14 +738,13 @@ run (void *cls,
        merchant_url,
        exchange_url,
        MHD_HTTP_NOT_FOUND,
-       "default",
        "tip 5",
        "EUR:5.01",
        TALER_EC_TIP_AUTHORIZE_INSTANCE_DOES_NOT_TIP),
 
     TALER_TESTING_cmd_tip_pickup_with_ec
       ("pickup-tip-3-too-much",
-       merchant_url,
+       merchant_tip_instance_url,
        MHD_HTTP_CONFLICT,
        "authorize-tip-1",
        pickup_amounts_1,
@@ -749,7 +755,7 @@ run (void *cls,
 
     TALER_TESTING_cmd_tip_pickup_with_ec
       ("pickup-non-existent-id",
-       merchant_url,
+       merchant_tip_instance_url,
        MHD_HTTP_NOT_FOUND,
        "fake-tip-authorization",
        pickup_amounts_1,
@@ -757,7 +763,7 @@ run (void *cls,
 
     TALER_TESTING_cmd_proposal
       ("create-proposal-tip-1",
-       merchant_url,
+       merchant_tip_instance_url,
        MHD_HTTP_OK,
        "{\"max_fee\":\
           {\"currency\":\"EUR\",\
@@ -773,11 +779,10 @@ run (void *cls,
         \"summary\": \"useful product\",\
         \"fulfillment_url\": \"https://example.com/\",\
         \"products\": [ {\"description\":\"ice cream\",\
-                         \"value\":\"{EUR:5}\"} ] }",
-        NULL),
+                         \"value\":\"{EUR:5}\"} ] }"),
 
     TALER_TESTING_cmd_pay ("deposit-tip-simple",
-                           merchant_url,
+                           merchant_tip_instance_url,
                            MHD_HTTP_OK,
                            "create-proposal-tip-1",
                            "pickup-tip-1",
@@ -849,8 +854,7 @@ run (void *cls,
         \"summary\": \"merchant-lib testcase\",\
         \"fulfillment_url\": \"https://example.com/\",\
         \"products\": [ {\"description\":\"ice cream\",\
-                         \"value\":\"{EUR:10}\"} ] }",
-        NULL),
+                         \"value\":\"{EUR:10}\"} ] }"),
 
     TALER_TESTING_cmd_pay ("pay-fail-partial-double-10",
                            merchant_url,
@@ -929,8 +933,7 @@ run (void *cls,
         \"summary\": \"merchant-lib testcase\",\
         \"fulfillment_url\": \"https://example.com/\",\
         \"products\": [ {\"description\":\"ice cream\",\
-                         \"value\":\"{EUR:10}\"} ] }",
-        NULL),
+                         \"value\":\"{EUR:10}\"} ] }"),
 
     TALER_TESTING_cmd_pay ("pay-fail-partial-double-11-good",
                            merchant_url,
@@ -1008,7 +1011,7 @@ run (void *cls,
        merchant_url,
        MHD_HTTP_OK,
        GNUNET_TIME_UNIT_ZERO_ABS,
-       5, /* Expected number of records */
+       4, /* Expected number of records */
        -100), /* Delta */
     /**
      * End the suite.  Fixme: better to have a label for this
@@ -1043,6 +1046,19 @@ main (int argc,
       (merchant_url = TALER_TESTING_prepare_merchant (CONFIG_FILE)))
     return 77;
 
+  merchant_tip_instance_url = TALER_url_join (merchant_url,
+                                              "instances/tip/",
+                                              NULL);
+  merchant_tip_instance_2_url = TALER_url_join (merchant_url,
+                                                "instances/dtip/",
+                                                NULL);
+  merchant_tip_instance_nulltip_url = TALER_url_join (merchant_url,
+                                                      "instances/nulltip/",
+                                                      NULL);
+  merchant_tip_unknown_instance_url = TALER_url_join (merchant_url,
+                                                      "instances/foo/",
+                                                      NULL);
+
   TALER_TESTING_cleanup_files (CONFIG_FILE);
 
   switch (TALER_TESTING_prepare_exchange (CONFIG_FILE,
diff --git a/src/lib/test_merchant_api_twisted.c b/src/lib/test_merchant_api_twisted.c
index 43f3ef6f..901823f4 100644
--- a/src/lib/test_merchant_api_twisted.c
+++ b/src/lib/test_merchant_api_twisted.c
@@ -75,6 +75,16 @@ static char *twister_exchange_url;
 static char *twister_merchant_url;
 
 /**
+ * Twister URL that proxies the merchant.
+ */
+static char *twister_merchant_url_instance_nonexistent;
+
+/**
+ * Twister URL that proxies the merchant.
+ */
+static char *twister_merchant_url_instance_tor;
+
+/**
  * URL of the fakebank.  Obtained from CONFIG_FILE's
  * "exchange-wire-test:BANK_URI" option.
  */
@@ -238,8 +248,7 @@ run (void *cls,
            \"fraction\":0},\
         \"summary\": \"merchant-lib testcase\",\
         \"products\": [ {\"description\":\"triggering bug 5719\",\
-                         \"value\":\"{EUR:1}\"} ] }",
-        NULL),
+                         \"value\":\"{EUR:1}\"} ] }"),
 
     /**
      * Instruct the Twister to malform the response given by
@@ -285,8 +294,7 @@ run (void *cls,
            \"fraction\":0},\
         \"summary\": \"merchant-lib testcase\",\
         \"products\": [ {\"description\":\"ice cream\",\
-                         \"value\":\"{EUR:3}\"} ] }",
-       NULL),
+                         \"value\":\"{EUR:3}\"} ] }"),
 
     /* Need any response code != 200.  */
     TALER_TESTING_cmd_hack_response_code
@@ -344,8 +352,7 @@ run (void *cls,
        MHD_HTTP_BAD_REQUEST,
        /* giving a valid JSON to not make it fail before
         * data reaches the merchant.  */
-       "{\"not\": \"used\"}",
-       NULL),
+       "{\"not\": \"used\"}"),
   
     TALER_TESTING_cmd_hack_response_code
       ("proposal-500",
@@ -360,8 +367,7 @@ run (void *cls,
        MHD_HTTP_INTERNAL_SERVER_ERROR,
        /* giving a valid JSON to not make it fail before
         * data reaches the merchant.  */
-       "{\"not\": \"used\"}",
-       NULL),
+       "{\"not\": \"used\"}"),
   
     /**
      * Cause the PUT /proposal callback to be called
@@ -390,8 +396,7 @@ run (void *cls,
            \"fraction\":0},\
         \"summary\": \"merchant-lib testcase\",\
         \"products\": [ {\"description\":\"ice cream\",\
-                         \"value\":\"{EUR:5}\"} ] }",
-        NULL),
+                         \"value\":\"{EUR:5}\"} ] }"),
     /**
      * Cause proposal to be invalid: this is achieved
      * by deleting the "order_id" field of it.
@@ -417,20 +422,18 @@ run (void *cls,
             \"fraction\":0},\
          \"summary\": \"merchant-lib testcase\",\
          \"products\": [ {\"description\":\"ice cream\",\
-                          \"value\":\"{EUR:5}\"} ] }",
-         NULL),
+                          \"value\":\"{EUR:5}\"} ] }"),
     /**
      * Cause a 404 Not Found response code,
      * due to a non existing merchant instance.
      */
     TALER_TESTING_cmd_proposal
       ("create-proposal-4",
-       twister_merchant_url,
+       twister_merchant_url_instance_nonexistent,
        MHD_HTTP_NOT_FOUND,
        "{\"amount\":\"EUR:5\",\
          \"fulfillment_url\": \"https://example.com/\",\
-         \"summary\": \"merchant-lib testcase\"}",
-       "non-existent-instance"),
+         \"summary\": \"merchant-lib testcase\"}"),
 
     /* Cause a 404 Not Found from /proposal/lookup,
      * due to a non existing order id being queried.  */
@@ -476,8 +479,7 @@ run (void *cls,
         \"fulfillment_url\": \"https://example.com/\",\
         \"summary\": \"merchant-lib testcase\",\
         \"products\": [ {\"description\":\"ice cream\",\
-                         \"value\":\"{EUR:5}\"} ] }",
-        NULL),
+                         \"value\":\"{EUR:5}\"} ] }"),
 
     /* Remove expected field.  */
     TALER_TESTING_cmd_delete_object ("remove-contract-terms",
@@ -569,7 +571,11 @@ run (void *cls,
 
     TALER_TESTING_cmd_proposal
       ("create-proposal-unaggregation",
-       twister_merchant_url,
+       /* Need a fresh instance in order to associate this
+        * proposal with a fresh h_wire;  this way, this proposal
+        * won't get hooked by the aggregator gathering same-H_wire'd
+        * transactions.  */
+       twister_merchant_url_instance_tor,
        MHD_HTTP_OK,
        "{\"max_fee\":\
           {\"currency\":\"EUR\",\
@@ -578,7 +584,6 @@ run (void *cls,
         \"refund_deadline\":\"\\/Date(2)\\/\",\
         \"pay_deadline\":\"\\/Date(1)\\/\",\
         \"wire_transfer_delay\":\"\\/Delay(30000)\\/\",\
-        \"instance\":\"tor\",\
         \"amount\":\
           {\"currency\":\"EUR\",\
            \"value\":5,\
@@ -586,12 +591,7 @@ run (void *cls,
         \"summary\": \"unaggregated product\",\
         \"fulfillment_url\": \"https://example.com/\",\
         \"products\": [ {\"description\":\"unaggregated cream\",\
-                         \"value\":\"{EUR:5}\"} ] }",
-        /* Need a fresh instance in order to associate this
-         * proposal with a fresh h_wire;  this way, this proposal
-         * won't get hooked by the aggregator gathering same-H_wire'd
-         * transactions.  */
-        "tor"),
+                         \"value\":\"{EUR:5}\"} ] }"),
 
     TALER_TESTING_cmd_pay
       ("pay-unaggregation",
@@ -652,8 +652,7 @@ run (void *cls,
            \"fraction\":0},\
         \"summary\": \"merchant-lib testcase\",\
         \"products\": [ {\"description\":\"ice cream\",\
-                         \"value\":\"{EUR:2}\"} ] }",
-        NULL),
+                         \"value\":\"{EUR:2}\"} ] }"),
     TALER_TESTING_cmd_pay ("deposit-simple-5383",
                            twister_merchant_url,
                            MHD_HTTP_OK,
@@ -744,8 +743,7 @@ run (void *cls,
            \"fraction\":0},\
         \"summary\": \"merchant-lib testcase\",\
         \"products\": [ {\"description\":\"ice cream\",\
-                         \"value\":\"{EUR:3}\"} ] }",
-        NULL),
+                         \"value\":\"{EUR:3}\"} ] }"),
 
     TALER_TESTING_cmd_check_payment ("check-payment-1",
                                      twister_merchant_url,
@@ -862,8 +860,7 @@ run (void *cls,
            \"fraction\":0},\
         \"summary\": \"merchant-lib testcase\",\
         \"products\": [ {\"description\":\"ice cream\",\
-                         \"value\":\"{EUR:3}\"} ] }",
-        NULL),
+                         \"value\":\"{EUR:3}\"} ] }"),
 
     /* Will only pay _half_ the supposed price,
      * so we'll then have the right to abort.  */
@@ -948,8 +945,7 @@ run (void *cls,
            \"value\":1,\
            \"fraction\":0},\
         \"summary\": \"merchant-lib testcase\",\
-        \"products\": [ {\"description\": \"will succeed\"}] }",
-        NULL),
+        \"products\": [ {\"description\": \"will succeed\"}] }"),
 
     TALER_TESTING_cmd_proposal
       ("create-proposal-double-spend-1",
@@ -968,8 +964,7 @@ run (void *cls,
            \"value\":1,\
            \"fraction\":0},\
         \"summary\": \"merchant-lib testcase\",\
-        \"products\": [ {\"description\": \"will fail\"}] }",
-        NULL),
+        \"products\": [ {\"description\": \"will fail\"}] }"),
 
     TALER_TESTING_cmd_withdraw_amount
       ("withdraw-coin-double-spend",
@@ -1087,6 +1082,9 @@ main (int argc,
       (PROXY_MERCHANT_CONFIG_FILE)))
     return 77;
 
+  twister_merchant_url_instance_nonexistent = TALER_url_join (twister_exchange_url, "instances/foo/", NULL);
+  twister_merchant_url_instance_tor = TALER_url_join (twister_exchange_url, "instances/tor/", NULL);
+
   TALER_TESTING_cleanup_files (CONFIG_FILE);
 
   switch (TALER_TESTING_prepare_exchange (CONFIG_FILE,
diff --git a/src/lib/testing_api_cmd_history.c b/src/lib/testing_api_cmd_history.c
index c9792680..6704fb93 100644
--- a/src/lib/testing_api_cmd_history.c
+++ b/src/lib/testing_api_cmd_history.c
@@ -43,11 +43,6 @@ struct HistoryState
   unsigned int http_status;
 
   /**
-   * The merchant instance executing this CMD.
-   */
-  const char *instance;
-
-  /**
    * URL of the merchant backend serving the /history request.
    */
   const char *merchant_url;
@@ -272,7 +267,6 @@ history_run (void *cls,
     hs->ho = TALER_MERCHANT_history_default_start
       (is->ctx,
        hs->merchant_url,
-       "default",
        hs->nrows,
        hs->time,
        &history_cb,
@@ -282,7 +276,6 @@ history_run (void *cls,
     case GNUNET_NO:
     hs->ho = TALER_MERCHANT_history (is->ctx,
                                      hs->merchant_url,
-                                     "default",
                                      hs->start,
                                      hs->nrows,
                                      hs->time,
diff --git a/src/lib/testing_api_cmd_pay.c b/src/lib/testing_api_cmd_pay.c
index 7f1c82a7..3be5d8dd 100644
--- a/src/lib/testing_api_cmd_pay.c
+++ b/src/lib/testing_api_cmd_pay.c
@@ -386,7 +386,6 @@ check_payment_run (void *cls,
   cps->cpo = TALER_MERCHANT_check_payment
                (is->ctx,
                cps->merchant_url,
-               "default", // only default instance for now.
                order_id,
                NULL,
                check_payment_cb,
@@ -854,7 +853,6 @@ _pay_run (const char *merchant_url,
 
   ret = api_func (is->ctx,
                   merchant_url,
-                  "default", // instance
                   h_proposal,
                   &total_amount,
                   &max_fee,
diff --git a/src/lib/testing_api_cmd_proposal.c b/src/lib/testing_api_cmd_proposal.c
index f095f38f..f5e282c9 100644
--- a/src/lib/testing_api_cmd_proposal.c
+++ b/src/lib/testing_api_cmd_proposal.c
@@ -79,11 +79,6 @@ struct ProposalState
   struct GNUNET_CRYPTO_EddsaPublicKey nonce;
 
   /**
-   * The merchant instance.
-   */
-  const char *instance;
-
-  /**
    * URL of the merchant backend.
    */
   const char *merchant_url;
@@ -318,7 +313,6 @@ proposal_cb (void *cls,
                    (ps->is->ctx,
                    ps->merchant_url,
                    ps->order_id,
-                   ps->instance,
                    &ps->nonce,
                    &proposal_lookup_initial_cb,
                    ps)))
@@ -376,18 +370,6 @@ proposal_run (void *cls,
     (GNUNET_CRYPTO_QUALITY_WEAK,
     &ps->nonce,
     sizeof (struct GNUNET_CRYPTO_EddsaPublicKey));
-  if (NULL != ps->instance)
-  {
-    json_t *merchant;
-
-    merchant = json_object ();
-    json_object_set_new (merchant,
-                         "instance",
-                         json_string (ps->instance));
-    json_object_set_new (order,
-                         "merchant",
-                         merchant);
-  }
 
   ps->po = TALER_MERCHANT_order_put (is->ctx,
                                      ps->merchant_url,
@@ -468,7 +450,6 @@ proposal_lookup_cleanup (void *cls,
  *        the proposal request.
  * @param http_status expected HTTP status.
  * @param order the order to PUT to the merchant.
- * @param instance merchant instance performing the operation.
  *
  * @return the command
  */
@@ -476,8 +457,7 @@ struct TALER_TESTING_Command
 TALER_TESTING_cmd_proposal (const char *label,
                             const char *merchant_url,
                             unsigned int http_status,
-                            const char *order,
-                            const char *instance)
+                            const char *order)
 {
   struct ProposalState *ps;
 
@@ -485,7 +465,6 @@ TALER_TESTING_cmd_proposal (const char *label,
   ps->order = order;
   ps->http_status = http_status;
   ps->merchant_url = merchant_url;
-  ps->instance = (NULL == instance) ? "default" : instance;
 
   struct TALER_TESTING_Command cmd = {
     .cls = ps,
@@ -580,7 +559,6 @@ proposal_lookup_run (void *cls,
   pls->plo = TALER_MERCHANT_proposal_lookup (is->ctx,
                                              pls->merchant_url,
                                              order_id,
-                                             "default",
                                              nonce,
                                              &proposal_lookup_cb,
                                              pls);
diff --git a/src/lib/testing_api_cmd_refund.c b/src/lib/testing_api_cmd_refund.c
index abe68f8e..f0ee31b5 100644
--- a/src/lib/testing_api_cmd_refund.c
+++ b/src/lib/testing_api_cmd_refund.c
@@ -221,7 +221,6 @@ refund_increase_run (void *cls,
                                              ris->order_id,
                                              &refund_amount,
                                              ris->reason,
-                                             "default",
                                              &refund_increase_cb,
                                              ris);
   GNUNET_assert (NULL != ris->rio);
@@ -450,7 +449,6 @@ refund_lookup_run (void *cls,
   rls->rlo = TALER_MERCHANT_refund_lookup (is->ctx,
                                            rls->merchant_url,
                                            rls->order_id,
-                                           "default",
                                            &refund_lookup_cb,
                                            rls);
   GNUNET_assert (NULL != rls->rlo);
diff --git a/src/lib/testing_api_cmd_tip.c b/src/lib/testing_api_cmd_tip.c
index 652bd95d..a5bbf2a1 100644
--- a/src/lib/testing_api_cmd_tip.c
+++ b/src/lib/testing_api_cmd_tip.c
@@ -139,11 +139,6 @@ struct TipQueryState
   unsigned int http_status;
 
   /**
-   * Which merchant instance is running this CMD.
-   */
-  const char *instance;
-
-  /**
    * The handle to the current /tip-query request.
    */
   struct TALER_MERCHANT_TipQueryOperation *tqo;
@@ -188,11 +183,6 @@ struct TipAuthorizeState
   unsigned int http_status;
 
   /**
-   * Merchant instance running this CMD.
-   */
-  const char *instance;
-
-  /**
    * Human-readable justification for the
    * tip authorization carried on by this CMD.
    */
@@ -345,7 +335,6 @@ tip_authorize_run (void *cls,
      "http://merchant.com/pickup",
      "http://merchant.com/continue",
      &amount,
-     tas->instance,
      tas->justification,
      tip_authorize_cb,
      tas);
@@ -411,7 +400,6 @@ tip_authorize_cleanup (void *cls,
  *        the reserve from which the tip is going to be gotten.
  * @param http_status the HTTP response code which is expected
  *        for this operation.
- * @param instance which merchant instance is running this CMD.
  * @param justification human-readable justification for this
  *        tip authorization.
  * @param amount the amount to authorize for tipping.
@@ -423,7 +411,6 @@ TALER_TESTING_cmd_tip_authorize_with_ec
    const char *merchant_url,
    const char *exchange_url,
    unsigned int http_status,
-   const char *instance,
    const char *justification,
    const char *amount,
    enum TALER_ErrorCode ec)
@@ -432,7 +419,6 @@ TALER_TESTING_cmd_tip_authorize_with_ec
 
   tas = GNUNET_new (struct TipAuthorizeState);
   tas->merchant_url = merchant_url;
-  tas->instance = instance;
   tas->justification = justification;
   tas->amount = amount;
   tas->http_status = http_status;
@@ -461,7 +447,6 @@ TALER_TESTING_cmd_tip_authorize_with_ec
  *        the reserve from which the tip is going to be gotten.
  * @param http_status the HTTP response code which is expected
  *        for this operation.
- * @param instance which merchant instance is running this CMD.
  * @param justification human-readable justification for this
  *        tip authorization.
  * @param amount the amount to authorize for tipping.
@@ -471,7 +456,6 @@ TALER_TESTING_cmd_tip_authorize (const char *label,
                                  const char *merchant_url,
                                  const char *exchange_url,
                                  unsigned int http_status,
-                                 const char *instance,
                                  const char *justification,
                                  const char *amount)
 {
@@ -479,7 +463,6 @@ TALER_TESTING_cmd_tip_authorize (const char *label,
 
   tas = GNUNET_new (struct TipAuthorizeState);
   tas->merchant_url = merchant_url;
-  tas->instance = instance;
   tas->justification = justification;
   tas->amount = amount;
   tas->http_status = http_status;
@@ -631,7 +614,6 @@ tip_query_run (void *cls,
   tqs->is = is;
   tqs->tqo = TALER_MERCHANT_tip_query (is->ctx,
                                        tqs->merchant_url,
-                                       tqs->instance,
                                        &tip_query_cb,
                                        tqs);
   GNUNET_assert (NULL != tqs->tqo);
@@ -646,7 +628,6 @@ tip_query_run (void *cls,
  *        server the /tip-query request.
  * @param http_status expected HTTP response code for the
  *        /tip-query request.
- * @param instance the merchant instance running this CMD.
  * @param expected_amount_picked_up expected amount already
  *        picked up.
  * @param expected_amount_authorized expected amount that was
@@ -660,7 +641,6 @@ TALER_TESTING_cmd_tip_query_with_amounts
   (const char *label,
    const char *merchant_url,
    unsigned int http_status,
-   const char *instance,
    const char *expected_amount_picked_up,
    const char *expected_amount_authorized,
    const char *expected_amount_available)
@@ -669,7 +649,6 @@ TALER_TESTING_cmd_tip_query_with_amounts
 
   tqs = GNUNET_new (struct TipQueryState);
   tqs->merchant_url = merchant_url;
-  tqs->instance = instance;
   tqs->http_status = http_status;
   tqs->expected_amount_picked_up = expected_amount_picked_up;
   tqs->expected_amount_authorized = expected_amount_authorized;
@@ -694,19 +673,16 @@ TALER_TESTING_cmd_tip_query_with_amounts
  *        server the /tip-query request.
  * @param http_status expected HTTP response code for the
  *        /tip-query request.
- * @param instance the merchant instance running this CMD.
  */
 struct TALER_TESTING_Command
 TALER_TESTING_cmd_tip_query (const char *label,
                              const char *merchant_url,
-                             unsigned int http_status,
-                             const char *instance)
+                             unsigned int http_status)
 {
   struct TipQueryState *tqs;
 
   tqs = GNUNET_new (struct TipQueryState);
   tqs->merchant_url = merchant_url;
-  tqs->instance = instance;
   tqs->http_status = http_status;
 
   struct TALER_TESTING_Command cmd = {
diff --git a/src/lib/testing_api_cmd_track.c b/src/lib/testing_api_cmd_track.c
index 9cd4803b..1f1596a4 100644
--- a/src/lib/testing_api_cmd_track.c
+++ b/src/lib/testing_api_cmd_track.c
@@ -373,7 +373,6 @@ track_transfer_run (void *cls,
     TALER_TESTING_FAIL (is);
   tts->tth = TALER_MERCHANT_track_transfer (is->ctx,
                                             tts->merchant_url,
-                                            "default",
                                             "x-taler-bank",
                                             wtid,
                                             exchange_url,
@@ -412,7 +411,6 @@ track_transaction_run (void *cls,
   tts->tth = TALER_MERCHANT_track_transaction
     (is->ctx,
      tts->merchant_url,
-     "default",
      order_id,
      &track_transaction_cb,
      tts);