diff --git a/flex_marketplace/src/lib.cairo b/flex_marketplace/src/lib.cairo
index aaae449..17d8e2a 100644
--- a/flex_marketplace/src/lib.cairo
+++ b/flex_marketplace/src/lib.cairo
@@ -1,8 +1,9 @@
 use core::fmt::{Display, Error, Formatter, Debug};
+use starknet::contract_address_to_felt252;
 
 impl DisplayContractAddress of Display<starknet::ContractAddress> {
     fn fmt(self: @starknet::ContractAddress, ref f: Formatter) -> Result<(), Error> {
-        write!(f, "{}", *self)
+        write!(f, "{}", contract_address_to_felt252(*self))
     }
 }
 
diff --git a/flex_marketplace/src/marketplace/transfer_selector_NFT.cairo b/flex_marketplace/src/marketplace/transfer_selector_NFT.cairo
index b1b776d..cdb4130 100644
--- a/flex_marketplace/src/marketplace/transfer_selector_NFT.cairo
+++ b/flex_marketplace/src/marketplace/transfer_selector_NFT.cairo
@@ -1,5 +1,6 @@
 use starknet::ContractAddress;
 
+
 #[starknet::interface]
 trait ITransferSelectorNFT<TState> {
     fn initializer(
@@ -123,7 +124,7 @@ mod TransferSelectorNFT {
             let transfer_manager = self.transfer_manager_selector_for_collection.read(collection);
             assert!(
                 !transfer_manager.is_zero(),
-                "TransferSelectorNFT: invalid transfer manager {}",
+                "TransferSelectorNFT: tried to remove an invalid transfer manager: {}",
                 transfer_manager
             );
             self
@@ -138,10 +139,12 @@ mod TransferSelectorNFT {
         }
 
         fn update_TRANSFER_MANAGER_ERC721(ref self: ContractState, manager: ContractAddress) {
+            self.ownable.assert_only_owner();
             self.TRANSFER_MANAGER_ERC721.write(manager);
         }
 
         fn update_TRANSFER_MANAGER_ERC1155(ref self: ContractState, manager: ContractAddress) {
+            self.ownable.assert_only_owner();
             self.TRANSFER_MANAGER_ERC1155.write(manager);
         }
 
diff --git a/flex_marketplace/tests/transfer_selector_nft_test.cairo b/flex_marketplace/tests/transfer_selector_nft_test.cairo
index 1e4644f..023f424 100644
--- a/flex_marketplace/tests/transfer_selector_nft_test.cairo
+++ b/flex_marketplace/tests/transfer_selector_nft_test.cairo
@@ -1,58 +1,107 @@
-use tests::utils::{setup, initialize_test};
+use starknet::{ContractAddress, contract_address_const};
+use snforge_std::{start_prank, CheatTarget};
+use flex::marketplace::transfer_selector_NFT::{
+    TransferSelectorNFT, ITransferSelectorNFTDispatcher, ITransferSelectorNFTDispatcherTrait
+};
+use tests::utils::{setup, initialize_test, OWNER, ZERO_ADDRESS, ACCOUNT1};
+
+fn COLLECTION() -> ContractAddress {
+    contract_address_const::<'COLLECTION'>()
+}
 
 #[test]
 fn test_add_collection_transfer_manager_success() {
     let dsp = setup();
     initialize_test(dsp);
-// TODO
+    start_prank(CheatTarget::One(dsp.transfer_selector.contract_address), OWNER());
+    dsp
+        .transfer_selector
+        .add_collection_transfer_manager(
+            COLLECTION(), dsp.transfer_manager_erc721.contract_address
+        );
+
+    let actual_transfer_manager = dsp
+        .transfer_selector
+        .get_transfer_manager_selector_for_collection(COLLECTION());
+    assert!(
+        actual_transfer_manager == dsp.transfer_manager_erc721.contract_address,
+        "Wrong transfer manager set"
+    );
 }
 
 #[test]
-#[should_panic()]
+#[should_panic(expected: ("TransferSelectorNFT: invalid collection 0",))]
 fn test_add_collection_transfer_manager_fails_invalid_collection() {
     let dsp = setup();
     initialize_test(dsp);
-    assert(false, '');
-// TODO
+
+    start_prank(CheatTarget::One(dsp.transfer_selector.contract_address), OWNER());
+    dsp
+        .transfer_selector
+        .add_collection_transfer_manager(
+            ZERO_ADDRESS(), dsp.transfer_manager_erc721.contract_address
+        );
 }
 
 #[test]
-#[should_panic()]
+#[should_panic(expected: ("TransferSelectorNFT: invalid transfer manager 0",))]
 fn test_add_collection_transfer_manager_fails_invalid_transfer_manager() {
     let dsp = setup();
     initialize_test(dsp);
-    assert(false, '');
-// TODO
+
+    start_prank(CheatTarget::One(dsp.transfer_selector.contract_address), OWNER());
+    dsp.transfer_selector.add_collection_transfer_manager(COLLECTION(), ZERO_ADDRESS());
 }
 
 #[test]
 fn test_remove_collection_transfer_manager_success() {
     let dsp = setup();
     initialize_test(dsp);
-// TODO
+
+    start_prank(CheatTarget::One(dsp.transfer_selector.contract_address), OWNER());
+    dsp
+        .transfer_selector
+        .add_collection_transfer_manager(
+            COLLECTION(), dsp.transfer_manager_erc721.contract_address
+        );
+
+    dsp.transfer_selector.remove_collection_transfer_manager(COLLECTION());
+    let actual_transfer_manager = dsp
+        .transfer_selector
+        .get_transfer_manager_selector_for_collection(COLLECTION());
+    assert!(actual_transfer_manager == ZERO_ADDRESS(), "Wrong transfer manager removed");
 }
 
 #[test]
-#[should_panic()]
+#[should_panic(expected: ("TransferSelectorNFT: tried to remove an invalid transfer manager: 0",))]
 fn test_remove_collection_transfer_manager_fails_invalid_transfer_manager() {
     let dsp = setup();
     initialize_test(dsp);
-    assert(false, '');
-// TODO
+
+    start_prank(CheatTarget::One(dsp.transfer_selector.contract_address), OWNER());
+    dsp.transfer_selector.remove_collection_transfer_manager(COLLECTION());
 }
 
 #[test]
 fn test_update_TRANSFER_MANAGER_ERC721_success() {
     let dsp = setup();
     initialize_test(dsp);
-// TODO
+
+    start_prank(CheatTarget::One(dsp.transfer_selector.contract_address), OWNER());
+    dsp.transfer_selector.update_TRANSFER_MANAGER_ERC721(ACCOUNT1());
+    let new_manager = dsp.transfer_selector.get_TRANSFER_MANAGER_ERC721();
+    assert(new_manager == ACCOUNT1(), 'wrong new manager');
 }
 
 #[test]
 fn test_update_TRANSFER_MANAGER_ERC1155_success() {
     let dsp = setup();
     initialize_test(dsp);
-// TODO
+
+    start_prank(CheatTarget::One(dsp.transfer_selector.contract_address), OWNER());
+    dsp.transfer_selector.update_TRANSFER_MANAGER_ERC1155(ACCOUNT1());
+    let new_manager = dsp.transfer_selector.get_TRANSFER_MANAGER_ERC1155();
+    assert(new_manager == ACCOUNT1(), 'wrong new manager');
 }
 
 // TESTS VIEWS
@@ -60,36 +109,32 @@ fn test_update_TRANSFER_MANAGER_ERC1155_success() {
 fn test_get_INTERFACE_ID_ERC721() {
     let dsp = setup();
     initialize_test(dsp);
-// TODO
+
+    assert!(dsp.transfer_selector.get_INTERFACE_ID_ERC721() == 0x80ac58cd, "wrong interface 721");
 }
+
 #[test]
 fn test_get_INTERFACE_ID_ERC1155() {
     let dsp = setup();
     initialize_test(dsp);
-// TODO
-}
-#[test]
-fn test_get_TRANSFER_MANAGER_ERC721() {
-    let dsp = setup();
-    initialize_test(dsp);
-// TODO
-}
-#[test]
-fn test_get_TRANSFER_MANAGER_ERC1155() {
-    let dsp = setup();
-    initialize_test(dsp);
-// TODO
-}
-#[test]
-fn test_get_transfer_manager_selector_for_collection() {
-    let dsp = setup();
-    initialize_test(dsp);
-// TODO
+
+    assert!(dsp.transfer_selector.get_INTERFACE_ID_ERC1155() == 0xd9b67a26, "wrong interface 1155");
 }
+
 #[test]
 fn test_check_transfer_manager_for_token() {
     let dsp = setup();
     initialize_test(dsp);
-// TODO
+    start_prank(CheatTarget::One(dsp.transfer_selector.contract_address), OWNER());
+    dsp
+        .transfer_selector
+        .add_collection_transfer_manager(
+            COLLECTION(), dsp.transfer_manager_erc721.contract_address
+        );
+
+    let actual_manager = dsp.transfer_selector.check_transfer_manager_for_token(COLLECTION());
+    assert(
+        actual_manager == dsp.transfer_manager_erc721.contract_address, 'wrong transfer manager'
+    );
 }
 
diff --git a/flex_marketplace/tests/utils.cairo b/flex_marketplace/tests/utils.cairo
index 045e2e2..ecf1b5f 100644
--- a/flex_marketplace/tests/utils.cairo
+++ b/flex_marketplace/tests/utils.cairo
@@ -71,6 +71,9 @@ fn ACCOUNT4() -> ContractAddress {
 fn PROXY_ADMIN() -> ContractAddress {
     contract_address_const::<'PROXY_ADMIN'>()
 }
+fn ZERO_ADDRESS() -> ContractAddress {
+    contract_address_const::<0>()
+}
 
 fn setup() -> Dispatchers {
     let contract = declare('MarketPlace');
@@ -143,9 +146,9 @@ fn initialize_test(dsp: Dispatchers) {
     dsp
         .transfer_selector
         .initializer(
-            PROXY_ADMIN(),
             dsp.transfer_manager_erc721.contract_address,
-            dsp.transfer_manager_erc1155.contract_address
+            dsp.transfer_manager_erc1155.contract_address,
+            OWNER(),
         );
     // Initialise TransferManagerNFT
     dsp