diff --git a/src/proto_alpha/lib_protocol/test/helpers/dummy_zk_rollup.ml b/src/proto_alpha/lib_protocol/test/helpers/dummy_zk_rollup.ml
index 070d69de6c603d06ab5eb31d640a0fbf9ffc251d..9dbb1ba55ba8e8cd49ba094e15a89039d5ba94b8 100644
--- a/src/proto_alpha/lib_protocol/test/helpers/dummy_zk_rollup.ml
+++ b/src/proto_alpha/lib_protocol/test/helpers/dummy_zk_rollup.ml
@@ -274,11 +274,13 @@ module V (L : LIB) = struct
       ~rollup_id op =
     let* old_state = input ~public:true @@ Input.bool old_state in
     let* new_state = input ~public:true @@ Input.bool new_state in
-    let* _fee =
+    let* (_fee : scalar repr) =
       input ~public:true
       @@ E.((fee_encoding ~safety:Bounded_e.Unsafe).input) fee
     in
-    let* _exit_validity = input ~public:true @@ Input.bool exit_validity in
+    let* (_exit_validity : bool repr) =
+      input ~public:true @@ Input.bool exit_validity
+    in
     let* rollup_id =
       input ~public:true @@ E.(tezos_pkh_encoding.input) rollup_id
     in
@@ -291,7 +293,7 @@ module V (L : LIB) = struct
   let predicate_batch ~old_state ~new_state ~fees ~rollup_id ops =
     let* old_state = input ~public:true @@ Input.bool old_state in
     let* new_state = input ~public:true @@ Input.bool new_state in
-    let* _fees =
+    let* (_fees : scalar repr) =
       input ~public:true
       @@ E.((amount_encoding ~safety:Bounded_e.Unsafe).input) fees
     in
@@ -312,7 +314,7 @@ module V (L : LIB) = struct
   let predicate_fees ~old_state ~new_state ~fees =
     let* old_state = input ~public:true @@ Input.bool old_state in
     let* new_state = input ~public:true @@ Input.bool new_state in
-    let* _fees =
+    let* (_fees : scalar repr) =
       input ~public:true
       @@ E.((amount_encoding ~safety:Bounded_e.Unsafe).input) fees
     in
diff --git a/src/proto_alpha/lib_protocol/test/helpers/incremental.ml b/src/proto_alpha/lib_protocol/test/helpers/incremental.ml
index da83665012c41cc6d45f10a8bb77e49d68b3650a..506b8e617094e7ac389e87c8ac91b1180687fb39 100644
--- a/src/proto_alpha/lib_protocol/test/helpers/incremental.ml
+++ b/src/proto_alpha/lib_protocol/test/helpers/incremental.ml
@@ -277,5 +277,5 @@ let finalize_block st =
 let assert_validate_operation_fails expect_failure op block =
   let open Lwt_result_syntax in
   let* i = begin_construction block in
-  let* _i = validate_operation ~expect_failure i op in
+  let* (_i : incremental) = validate_operation ~expect_failure i op in
   return_unit
diff --git a/src/proto_alpha/lib_protocol/test/integration/consensus/test_seed.ml b/src/proto_alpha/lib_protocol/test/integration/consensus/test_seed.ml
index c284eb3552aaab8f039658b62f8137fd6394e276..170b01f9c602b9fd8d30d830a2bdb860f56700c6 100644
--- a/src/proto_alpha/lib_protocol/test/integration/consensus/test_seed.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/consensus/test_seed.ml
@@ -92,7 +92,7 @@ let test_seed_no_commitment () =
       ()
   in
   let* b = check_seed b initial_seed in
-  let* _ = bake_and_check_seed b seeds in
+  let* (_ : Block.t) = bake_and_check_seed b seeds in
   return_unit
 
 (** Baking [blocks_per_commitment] blocks without a [seed_nonce_hash]
diff --git a/src/proto_alpha/lib_protocol/test/integration/michelson/test_patched_contracts.ml b/src/proto_alpha/lib_protocol/test/integration/michelson/test_patched_contracts.ml
index 8d6916166c85212366482d7f334fe35e921b5948..d5f13a418b5c3a990d10f24f01174f983eb3fd25 100644
--- a/src/proto_alpha/lib_protocol/test/integration/michelson/test_patched_contracts.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/michelson/test_patched_contracts.ml
@@ -165,7 +165,7 @@ module Legacy_patch_test (Patches : LEGACY_SCRIPT_PATCHES) :
     let* block, _contracts = Context.init3 () in
     let* inc = Incremental.begin_construction block in
     let ctxt = Incremental.alpha_ctxt inc in
-    let* _ =
+    let* _code, _ctxt =
       Lwt.map Environment.wrap_tzresult
       @@ Script_ir_translator.parse_code
            ~elab_conf:Script_ir_translator_config.(make ~legacy:false ())
diff --git a/src/proto_alpha/lib_protocol/test/integration/michelson/test_ticket_manager.ml b/src/proto_alpha/lib_protocol/test/integration/michelson/test_ticket_manager.ml
index 711a6974ec7a05869e3fa190f6614fd3073a7afe..37103dd9ebcd5422a3bc26d3fd22446951d702c3 100644
--- a/src/proto_alpha/lib_protocol/test/integration/michelson/test_ticket_manager.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/michelson/test_ticket_manager.ml
@@ -717,7 +717,7 @@ let test_create_contract_and_send_tickets () =
   (* Add a green ticket to the lazy storage at index 1 and send it to the green
      ticket-receiver *)
   let* b = test b @@ TM.add_lazy ~index:1 ~content:"Green" ~amount:10 in
-  let* _b =
+  let* (_b : Block.t) =
     test b @@ TM.send_lazy ~index:1 ~recipient:ticket_receiver_green_2
   in
   return ()
@@ -737,7 +737,9 @@ let test_add_remove_from_lazy_storage () =
   (* Remove the big-map. *)
   let* b = tm b TM.remove_all_lazy in
   (* Add back a ticket at index 1. *)
-  let* _b = tm b @@ TM.add_lazy ~index:1 ~content:"Red" ~amount:10 in
+  let* (_b : Block.t) =
+    tm b @@ TM.add_lazy ~index:1 ~content:"Red" ~amount:10
+  in
   return ()
 
 (** Test send to self and replace big-map. *)
@@ -750,7 +752,7 @@ let test_send_self_replace_big_map () =
   let* b = tm b @@ TM.add_lazy ~index:3 ~content:"Blue" ~amount:1 in
   let* b = tm b @@ TM.send_self_replace_big_map in
   let* b = tm b @@ TM.send_self_replace_big_map in
-  let* _b = tm b @@ TM.send_self_replace_big_map in
+  let* (_b : Block.t) = tm b @@ TM.send_self_replace_big_map in
   return ()
 
 (** Test add to and remove from strict storage. *)
@@ -766,7 +768,7 @@ let test_add_remove_strict () =
 
   (* Remove strict tickets *)
   let* b = tm b @@ TM.remove_strict in
-  let* _b = tm b @@ TM.add_strict ~content:"Red" ~amount:1 in
+  let* (_b : Block.t) = tm b @@ TM.add_strict ~content:"Red" ~amount:1 in
   return ()
 
 (** Test mixed operations. *)
@@ -782,7 +784,7 @@ let test_mixed_operations () =
   let* b = tm b @@ TM.add_lazy ~index:3 ~content:"Blue" ~amount:1 in
   (* Remove strict and lazy *)
   let* b = tm b @@ TM.remove_strict in
-  let* _b = tm b @@ TM.remove_all_lazy in
+  let* (_b : Block.t) = tm b @@ TM.remove_all_lazy in
   return ()
 
 let tests =
diff --git a/src/proto_alpha/lib_protocol/test/integration/operations/test_origination.ml b/src/proto_alpha/lib_protocol/test/integration/operations/test_origination.ml
index e7c455a04999b7b9664901dc9a5b1b0fe5e84362..03feece5006bf870751de7766371dadeb7131794 100644
--- a/src/proto_alpha/lib_protocol/test/integration/operations/test_origination.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/operations/test_origination.ml
@@ -255,7 +255,7 @@ let test_unparsable_script () =
   in
   (* Ensure that the application fails with [Ill_typed_contract]. *)
   let* i = Incremental.begin_construction b in
-  let* _i =
+  let* (_i : Incremental.t) =
     Incremental.add_operation
       ~expect_apply_failure:(function
         | Environment.Ecoproto_error (Script_tc_errors.Ill_typed_contract _)
@@ -296,7 +296,7 @@ let test_unparsable_script () =
   in
   (* Ensure that the operation is valid but the application fails with
      [Lazy_script_decode]. *)
-  let* _i =
+  let* (_i : Incremental.t) =
     Incremental.add_operation
       ~expect_apply_failure:(function
         | [Environment.Ecoproto_error Script.Lazy_script_decode] -> return_unit
diff --git a/src/proto_alpha/lib_protocol/test/integration/operations/test_paid_storage_increase.ml b/src/proto_alpha/lib_protocol/test/integration/operations/test_paid_storage_increase.ml
index 6d574b5af9e92843024ad466633894f45d03cc99..f233834607ebff63d2fe98d6d1434a332ff656c3 100644
--- a/src/proto_alpha/lib_protocol/test/integration/operations/test_paid_storage_increase.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/operations/test_paid_storage_increase.ml
@@ -233,7 +233,7 @@ let test_effectiveness () =
       contract_dst
       Tez.zero
   in
-  let+ _inc = Incremental.add_operation inc op in
+  let+ (_inc : Incremental.t) = Incremental.add_operation inc op in
   ()
 
 let tests =
diff --git a/src/proto_alpha/lib_protocol/test/integration/operations/test_sc_rollup.ml b/src/proto_alpha/lib_protocol/test/integration/operations/test_sc_rollup.ml
index 70ce655b20d152ef159ad878fd7c3a7fa2c5337c..c979c297afa3a84064f0440c27388d2d0f8c038b 100644
--- a/src/proto_alpha/lib_protocol/test/integration/operations/test_sc_rollup.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/operations/test_sc_rollup.ml
@@ -691,7 +691,9 @@ let test_publish_fails_on_backtrack () =
         return_unit
     | _ -> failwith "It should have failed with [Sc_rollup_staker_backtracked]"
   in
-  let* _ = Incremental.add_operation ~expect_apply_failure i operation2 in
+  let* (_ : Incremental.t) =
+    Incremental.add_operation ~expect_apply_failure i operation2
+  in
   return_unit
 
 (** [test_cement_fails_on_conflict] creates a rollup and then publishes
@@ -729,7 +731,9 @@ let test_cement_fails_on_conflict () =
         return_unit
     | _ -> failwith "It should have failed with [Sc_rollup_disputed]"
   in
-  let* _ = Incremental.add_operation ~expect_apply_failure i cement_op in
+  let* (_ : Incremental.t) =
+    Incremental.add_operation ~expect_apply_failure i cement_op
+  in
   return_unit
 
 let commit_and_cement_after_n_bloc ?expect_apply_failure block contract rollup n
@@ -744,7 +748,9 @@ let commit_and_cement_after_n_bloc ?expect_apply_failure block contract rollup n
   let* i = Incremental.begin_construction b in
   let* i, hash = hash_commitment i commitment in
   let* cement_op = Op.sc_rollup_cement (I i) contract rollup hash in
-  let* _ = Incremental.add_operation ?expect_apply_failure i cement_op in
+  let* (_ : Incremental.t) =
+    Incremental.add_operation ?expect_apply_failure i cement_op
+  in
   return_unit
 
 (** [test_challenge_window_period_boundaries] checks that cementing a commitment
@@ -1536,7 +1542,9 @@ let test_inbox_max_number_of_messages_per_commitment_period () =
           "It should have failed with \
            [Sc_rollup_max_number_of_messages_reached_for_commitment_period"
   in
-  let* _incr = Incremental.add_operation ~expect_apply_failure incr op in
+  let* (_incr : Incremental.t) =
+    Incremental.add_operation ~expect_apply_failure incr op
+  in
   return_unit
 
 let add_op block op =
@@ -1593,7 +1601,7 @@ let test_timeout () =
   let game_index = Sc_rollup.Game.Index.make pkh1 pkh2 in
   (* Testing to send a timeout before it's allowed. There is one block left
      before timeout is allowed, that is, the current block. *)
-  let* _incr =
+  let* (_incr : Incremental.t) =
     let expected_block_left = 0l in
     let expect_apply_failure = function
       | Environment.Ecoproto_error
@@ -1859,7 +1867,9 @@ let test_dissection_during_final_move () =
         return_unit
     | _ -> failwith "It should have failed with [Dissecting_during_final_move]"
   in
-  let* _incr = Incremental.add_operation ~expect_apply_failure incr p2_op in
+  let* (_incr : Incremental.t) =
+    Incremental.add_operation ~expect_apply_failure incr p2_op
+  in
   return_unit
 
 let init_arith_state ~boot_sector =
diff --git a/src/proto_alpha/lib_protocol/test/integration/operations/test_sc_rollup_transfer.ml b/src/proto_alpha/lib_protocol/test/integration/operations/test_sc_rollup_transfer.ml
index 18965a83f8bdd24ba9040e701bb20161b9fb79e4..7c7bcb3c799a4d7c5062506570970b6e124f494f 100644
--- a/src/proto_alpha/lib_protocol/test/integration/operations/test_sc_rollup_transfer.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/operations/test_sc_rollup_transfer.ml
@@ -168,7 +168,7 @@ let transfer ?expect_apply_failure b ~from ~to_ ~param ~entrypoint =
 let test_transfer_to_bad_sc_rollup_address () =
   let* b, c, contract, _rollup = context_init "unit" in
   let not_an_sc_rollup_address = {|"scr1HLXM32GacPNDrhHDLAssZG88eWqCUbyL"|} in
-  let* _b =
+  let* (_b : Block.t) =
     transfer
       b
       ~from:c
@@ -195,7 +195,7 @@ let test_transfer_to_bad_sc_rollup_address () =
 let test_transfer_to_unknown_sc_rollup_address () =
   let* b, c, contract, _rollup = context_init "unit" in
   let unknown_sc_rollup_address = {|"scr1HLXM32GacPNDrhHDLAssZG88eWqCUbyLF"|} in
-  let* _b =
+  let* (_b : Block.t) =
     transfer
       b
       ~from:c
@@ -219,7 +219,7 @@ let test_transfer_to_unknown_sc_rollup_address () =
 let test_transfer_to_wrongly_typed_sc_rollup () =
   let* b, c, contract, rollup = context_init "unit" in
   let param = Format.sprintf "%S" (Sc_rollup.Address.to_b58check rollup) in
-  let* _b =
+  let* (_b : Block.t) =
     transfer
       b
       ~from:c
@@ -243,7 +243,7 @@ let test_transfer_to_wrongly_typed_sc_rollup () =
 let test_transfer_non_zero_amount () =
   let* b, c, contract, rollup = context_init "int" in
   let param = Format.sprintf "%S" (Sc_rollup.Address.to_b58check rollup) in
-  let* _b =
+  let* (_b : Block.t) =
     transfer
       b
       ~from:c
@@ -270,7 +270,7 @@ let test_transfer_non_zero_amount_via_entrypoint () =
   let param =
     Format.sprintf "%S" (Sc_rollup.Address.to_b58check rollup ^ "%use_this_one")
   in
-  let* _b =
+  let* (_b : Block.t) =
     transfer
       b
       ~from:c
@@ -328,7 +328,7 @@ let test_transfer_works () =
 let test_transfer_zero_amount_ticket () =
   let* b, c, contract, rollup = context_init "ticket string" in
   let param = Format.sprintf "%S" (Sc_rollup.Address.to_b58check rollup) in
-  let* _b =
+  let* (_b : Block.t) =
     transfer
       b
       ~from:c
diff --git a/src/proto_alpha/lib_protocol/test/integration/operations/test_transfer.ml b/src/proto_alpha/lib_protocol/test/integration/operations/test_transfer.ml
index c31af4759b932cf1e9da7053e48b906c11e7d263..d1f81ea918d502193d51858a1055ffb3071103f3 100644
--- a/src/proto_alpha/lib_protocol/test/integration/operations/test_transfer.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/operations/test_transfer.ml
@@ -827,7 +827,9 @@ let test_storage_fees_and_internal_operation () =
   in
   (* Ensure success when the initial balance of the originated contract is
      sufficient to pay storage fees. *)
-  let+ _ = originate_and_call ~initial_state ~initial_amount:Tez.one_cent in
+  let+ (_ : State.t) =
+    originate_and_call ~initial_state ~initial_amount:Tez.one_cent
+  in
   ()
 
 let tests =
diff --git a/src/proto_alpha/lib_protocol/test/integration/operations/test_tx_rollup.ml b/src/proto_alpha/lib_protocol/test/integration/operations/test_tx_rollup.ml
index 69aea03cb08399b6e4847c46d9d7ea05273a09af..496d486b41703bb99efbb304c0b31a1bcf5a80b1 100644
--- a/src/proto_alpha/lib_protocol/test/integration/operations/test_tx_rollup.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/operations/test_tx_rollup.ml
@@ -3521,7 +3521,7 @@ module Rejection = struct
         l2_accounts
     in
     let time = time () in
-    let* _ = C.commit ~time store in
+    let* (_ : Context_hash.t) = C.commit ~time store in
     return store
 
   (** Regression test to ensure that we can reject a commitment where the
@@ -4034,7 +4034,9 @@ let test_state_message_storage_preallocation () =
   let ctxt = Incremental.alpha_ctxt i in
   let message, _ = Tx_rollup_message.make_batch "bogus" in
   let message_hash = Tx_rollup_message_hash.hash_uncarbonated message in
-  let _inbox_hash = Tx_rollup_inbox.Merkle.merklize_list [message_hash] in
+  let (_inbox_hash : Tx_rollup_inbox.Merkle.root) =
+    Tx_rollup_inbox.Merkle.merklize_list [message_hash]
+  in
   let state = Tx_rollup_state.initial_state ~pre_allocated_storage:Z.zero in
   let occupied_storage_before =
     Tx_rollup_state.Internal_for_tests.get_occupied_storage state
diff --git a/src/proto_alpha/lib_protocol/test/integration/operations/test_voting.ml b/src/proto_alpha/lib_protocol/test/integration/operations/test_voting.ml
index 8a2c400c9abab72b231b7f4f83eb82f0fa43819d..0f6d37978341f34fcdd74777f50b776682ac3d67 100644
--- a/src/proto_alpha/lib_protocol/test/integration/operations/test_voting.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/operations/test_voting.ml
@@ -1473,7 +1473,7 @@ let test_conflict_too_many_proposals () =
     Incremental.validate_operation current_block_state op_in_current_block
   in
   let* op = Op.proposals (B block) proposer [protos.(0)] in
-  let* _i =
+  let* (_i : Incremental.t) =
     Incremental.validate_operation
       ~expect_failure:(conflicting_proposals __LOC__)
       current_block_state
@@ -1493,7 +1493,7 @@ let test_conflicting_proposal () =
     Incremental.validate_operation current_block_state op_in_current_block
   in
   let* op = Op.proposals (B block) proposer [proposal] in
-  let* _i =
+  let* (_i : Incremental.t) =
     Incremental.validate_operation
       ~expect_failure:(conflicting_proposals __LOC__)
       current_block_state
@@ -1501,7 +1501,7 @@ let test_conflicting_proposal () =
   in
   let proposal' = protos.(1) in
   let* op' = Op.proposals (B block) proposer [proposal'] in
-  let* _i =
+  let* (_i : Incremental.t) =
     Incremental.validate_operation
       ~expect_failure:(conflicting_proposals __LOC__)
       current_block_state
@@ -1634,14 +1634,14 @@ let test_too_many_proposals_in_one_operation () =
   let open Lwt_result_syntax in
   let* b0, proposer0 = context_init1 () in
   let protos = Array.to_list protos in
-  let* _ =
-    try
-      let* _ = Op.proposals (B b0) proposer0 protos in
+  Lwt.catch
+    (fun () ->
+      let* (_ : packed_operation) = Op.proposals (B b0) proposer0 protos in
       failwith
-        "Encoding of proposals operation with too many proposals should fail"
-    with Data_encoding.Binary.(Write_error List_invalid_length) -> return_unit
-  in
-  return_unit
+        "Encoding of proposals operation with too many proposals should fail")
+    (function
+      | Data_encoding.Binary.(Write_error List_invalid_length) -> return_unit
+      | exn -> Lwt.fail exn)
 
 (* Bake blocks with various valid Proposals operations, and observe
    that their effects are correctly applied. *)
@@ -1838,7 +1838,7 @@ let test_conflicting_ballot () =
     Incremental.validate_operation current_block_state op_in_current_block
   in
   let* op = Op.ballot (B block) voter proposal Vote.Nay in
-  let* _i =
+  let* (_i : Incremental.t) =
     Incremental.validate_operation
       ~expect_failure:(conflicting_ballot __LOC__)
       current_block_state
diff --git a/src/proto_alpha/lib_protocol/test/integration/operations/test_zk_rollup.ml b/src/proto_alpha/lib_protocol/test/integration/operations/test_zk_rollup.ml
index e13d8fdd54a7bc648d281fdd2b7948a0939385a0..ce91e84403782b72d017300cc1e625f333e6bf3d 100644
--- a/src/proto_alpha/lib_protocol/test/integration/operations/test_zk_rollup.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/operations/test_zk_rollup.ml
@@ -97,7 +97,7 @@ let test_disable_feature_flag () =
       ~init_state:Operator.init_state
       ~nb_ops:1
   in
-  let* _i =
+  let* (_i : Incremental.t) =
     Incremental.add_operation
       ~expect_failure:
         (check_proto_error Validate_errors.Manager.Zk_rollup_feature_disabled)
@@ -183,7 +183,7 @@ let test_origination_negative_nb_ops () =
       ~nb_ops:(-1)
   in
   let* i = Incremental.begin_construction ctxt in
-  let* _i =
+  let* (_i : Incremental.t) =
     Incremental.add_operation
       ~expect_apply_failure:
         (check_proto_error Zk_rollup_apply.Zk_rollup_negative_nb_ops)
@@ -224,7 +224,7 @@ let test_originate_two_rollups () =
       ~init_state:Operator.init_state
       ~nb_ops:1
   in
-  let* _b = Block.bake ~operation ctxt in
+  let* (_b : Block.t) = Block.bake ~operation ctxt in
   assert (zk_rollup1 <> zk_rollup2) ;
   return_unit
 
@@ -265,7 +265,7 @@ let test_append_out_of_range_op_code () =
       ~zk_rollup
       ~ops:[no_ticket {l2_op with op_code = 1}]
   in
-  let* _i =
+  let* (_i : Incremental.t) =
     Incremental.add_operation
       ~expect_apply_failure:
         (check_proto_error (Zk_rollup_storage.Zk_rollup_invalid_op_code 1))
@@ -291,7 +291,7 @@ let test_append_external_deposit () =
       ~ops:
         [no_ticket {l2_op with price = {l2_op.price with amount = Z.of_int 10}}]
   in
-  let* _i =
+  let* (_i : Incremental.t) =
     Incremental.add_operation
       ~expect_apply_failure:
         (check_proto_error Zk_rollup.Errors.Deposit_as_external)
@@ -495,7 +495,7 @@ let test_append_errors () =
       ~zk_rollup
       ~ops:[({op with price}, Some ticket)]
   in
-  let* _i =
+  let* (_i : Incremental.t) =
     Incremental.add_operation
       ~expect_apply_failure:
         (check_proto_error Zk_rollup.Errors.Invalid_deposit_amount)
@@ -511,7 +511,7 @@ let test_append_errors () =
       ~zk_rollup
       ~ops:[no_ticket {op with price}]
   in
-  let* _i =
+  let* (_i : Incremental.t) =
     Incremental.add_operation
       ~expect_apply_failure:
         (check_proto_error Zk_rollup.Errors.Invalid_deposit_amount)
@@ -532,7 +532,7 @@ let test_append_errors () =
       ~zk_rollup
       ~ops:[({op with price}, Some ticket)]
   in
-  let* _i =
+  let* (_i : Incremental.t) =
     Incremental.add_operation
       ~expect_apply_failure:
         (check_proto_error Zk_rollup.Errors.Invalid_deposit_ticket)
@@ -725,7 +725,7 @@ let test_invalid_deposit () =
     let* constants = Context.get_constants (I i) in
     constants.parametric.tx_rollup.max_ticket_payload_size |> return
   in
-  let* _i =
+  let* (_i : Incremental.t) =
     let payload_size = Saturation_repr.safe_int (contents_size + 216) in
     Incremental.add_operation
       ~expect_apply_failure:
diff --git a/src/proto_alpha/lib_protocol/test/integration/test_sc_rollup_wasm.ml b/src/proto_alpha/lib_protocol/test/integration/test_sc_rollup_wasm.ml
index 46369c9f3f8062712f1cf6f63a03b548efcd72cf..7c39adddd6a6e47fedf603921bd2902b328156ce 100644
--- a/src/proto_alpha/lib_protocol/test/integration/test_sc_rollup_wasm.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/test_sc_rollup_wasm.ml
@@ -85,7 +85,9 @@ module WASM_P :
   let produce_proof context tree step =
     let open Lwt_syntax in
     let* context = Context_binary.add_tree context [] tree in
-    let _hash = Context_binary.commit ~time:Time.Protocol.epoch context in
+    let* (_hash : Context_hash.t) =
+      Context_binary.commit ~time:Time.Protocol.epoch context
+    in
     let index = Context_binary.index context in
     match Context_binary.Tree.kinded_key tree with
     | Some k ->
@@ -215,7 +217,7 @@ let should_boot_computation_kernel () =
     checked_set_input ~loc:__LOC__ context (arbitrary_input 0 "test") s
   in
   (* running until waiting for input *)
-  let* _s = eval_until_set_input context s in
+  let* (_s : Prover.state) = eval_until_set_input context s in
   return_unit
 
 let tests =
diff --git a/src/proto_alpha/lib_protocol/test/integration/test_storage.ml b/src/proto_alpha/lib_protocol/test/integration/test_storage.ml
index 60ed66fbc0c54cbff3ea9563776d8455a5b6e994..03485707c3ef3eb2c078f4f36e3aa618a8ec01e0 100644
--- a/src/proto_alpha/lib_protocol/test/integration/test_storage.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/test_storage.ml
@@ -128,7 +128,7 @@ let create_indexed_subcontext_int64
 
 let must_failwith f_prog error =
   try
-    let _ = f_prog () in
+    let () = f_prog () in
     Alcotest.fail "Unexpected successful result"
   with exc ->
     if exc = error then Lwt.return_unit
@@ -141,8 +141,12 @@ let must_failwith f_prog error =
 let test_register_single_data () =
   let f_prog () =
     let context = create_context "context1" in
-    let _single_data = create_single_data_storage "single_data" context in
-    create_single_data_storage "single_data" context
+    (create_single_data_storage "single_data" context
+      :> (module Single_data_storage))
+    |> ignore ;
+    (create_single_data_storage "single_data" context
+      :> (module Single_data_storage))
+    |> ignore
   in
   let error =
     Invalid_argument
@@ -159,9 +163,13 @@ let test_register_named_subcontext () =
   let f_prog () =
     let context = create_context "context2" in
     let subcontext = create_subcontext "sub_context" context in
-    let _single_data = create_single_data_storage "error_register" subcontext in
+    (create_single_data_storage "error_register" subcontext
+      :> (module Single_data_storage))
+    |> ignore ;
     let subcontext = create_subcontext "error_register" subcontext in
-    create_single_data_storage "single_data2" subcontext
+    (create_single_data_storage "single_data2" subcontext
+      :> (module Single_data_storage))
+    |> ignore
   in
   let error =
     Invalid_argument
@@ -177,8 +185,11 @@ let test_register_named_subcontext () =
 let test_register_indexed_subcontext () =
   let f_prog () =
     let context = create_context "context3" in
-    let _ = create_single_data_storage "single_value" context in
-    create_indexed_subcontext_int32 context
+    (create_single_data_storage "single_value" context
+      :> (module Single_data_storage))
+    |> ignore ;
+    (create_indexed_subcontext_int32 context :> (module Data_set_storage))
+    |> ignore
   in
   let error =
     Invalid_argument
@@ -195,8 +206,10 @@ let test_register_indexed_subcontext () =
 let test_register_indexed_subcontext_2 () =
   let f_prog () =
     let context = create_context "context4" in
-    let _ = create_indexed_subcontext_int32 context in
-    create_indexed_subcontext_int64 context
+    (create_indexed_subcontext_int32 context :> (module Data_set_storage))
+    |> ignore ;
+    (create_indexed_subcontext_int64 context :> (module Data_set_storage))
+    |> ignore
   in
   let error =
     Invalid_argument
diff --git a/src/proto_alpha/lib_protocol/test/integration/validate/manager_operation_helpers.ml b/src/proto_alpha/lib_protocol/test/integration/validate/manager_operation_helpers.ml
index 6f7af4cd1c5969fb19e6bc5116376cd7c2c71f13..ab2bd849f25b9cde5d68617f3778420f1a5c85d8 100644
--- a/src/proto_alpha/lib_protocol/test/integration/validate/manager_operation_helpers.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/validate/manager_operation_helpers.ml
@@ -327,7 +327,7 @@ let self_delegate block pkh =
   let* block = Block.bake block ~operation in
   let* del_opt_new = Context.Contract.delegate_opt (B block) contract in
   let* del = Assert.get_some ~loc:__LOC__ del_opt_new in
-  let+ _ = Assert.equal_pkh ~loc:__LOC__ del pkh in
+  let+ () = Assert.equal_pkh ~loc:__LOC__ del pkh in
   block
 
 let delegation block source delegate =
@@ -344,7 +344,7 @@ let delegation block source delegate =
   let* block = Block.bake block ~operation in
   let* del_opt_new = Context.Contract.delegate_opt (B block) contract_source in
   let* del = Assert.get_some ~loc:__LOC__ del_opt_new in
-  let+ _ = Assert.equal_pkh ~loc:__LOC__ del delegate_pkh in
+  let+ () = Assert.equal_pkh ~loc:__LOC__ del delegate_pkh in
   block
 
 let originate_tx_rollup block rollup_account =
@@ -1385,7 +1385,7 @@ let observe ~only_validate ~mode ctxt_pre ctxt_post op =
       (if only_validate then "Balance update (=)" else "Balance update (<=)")
       Tez.pp
   in
-  let* _ = b_cmp b_out b_expected in
+  let* () = b_cmp b_out b_expected in
   let _ =
     Assert.equal
       Z.equal
@@ -1525,7 +1525,7 @@ let validate_ko_diagnostic ?(mode = Construction) (infos : infos) ops
           infos.ctxt.block
           ~mempool_mode:(mempool_mode_of mode)
       in
-      let* _ = add_operations ~expect_failure i ops in
+      let* (_ : Incremental.t) = add_operations ~expect_failure i ops in
       return_unit
   | Application -> (
       let*! res =
diff --git a/src/proto_alpha/lib_protocol/test/integration/validate/test_1m_restriction.ml b/src/proto_alpha/lib_protocol/test/integration/validate/test_1m_restriction.ml
index 1431e708f43eb61e27b595c446ed5dcfe1a56a87..2e5ef078bcc4ec7fd69ebb48f7c49acf05e71fda 100644
--- a/src/proto_alpha/lib_protocol/test/integration/validate/test_1m_restriction.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/validate/test_1m_restriction.ml
@@ -108,7 +108,7 @@ let positive_tests =
       let open Lwt_result_syntax in
       let* infos = init_ctxt ctxt_req in
       let* op = select_op operation_req infos in
-      let* _infos = wrap_mode ~only_validate:true infos [op] mode in
+      let* (_infos : infos) = wrap_mode ~only_validate:true infos [op] mode in
       return_true)
 
 (** Under 1M restriction, neither a block nor a prevalidator's valid
@@ -146,7 +146,7 @@ let two_op_from_same_manager_tests =
       let* infos = init_ctxt ctxt_req in
       let* op1 = select_op operation_req infos in
       let* op2 = select_op operation_req2 infos in
-      let* _ = validate_ko_diagnostic ~mode infos [op1; op2] expect_failure in
+      let* () = validate_ko_diagnostic ~mode infos [op1; op2] expect_failure in
       return_true)
 
 (** Under 1M restriction, a batch of two operations cannot be replaced
@@ -175,8 +175,8 @@ let batch_is_not_singles_tests =
       let* batch =
         Op.batch_operations ~source (B infos.ctxt.block) [op1; op2]
       in
-      let* _ = only_validate_diagnostic ~mode infos [batch] in
-      let* _ = validate_ko_diagnostic ~mode infos [op1; op2] expect_failure in
+      let* (_ : infos) = only_validate_diagnostic ~mode infos [batch] in
+      let* () = validate_ko_diagnostic ~mode infos [op1; op2] expect_failure in
       return_true)
 
 (** The applications of two covalid operations in a certain context
@@ -213,8 +213,8 @@ let conflict_free_tests =
         }
       in
       let* op2 = select_op operation_req' infos2 in
-      let* _ = only_validate_diagnostic ~mode infos [op1; op2] in
-      let* _ = only_validate_diagnostic ~mode infos [op2; op1] in
+      let* (_ : infos) = only_validate_diagnostic ~mode infos [op1; op2] in
+      let* (_ : infos) = only_validate_diagnostic ~mode infos [op2; op1] in
       return_true)
 
 open Lib_test.Qcheck2_helpers
diff --git a/src/proto_alpha/lib_protocol/test/integration/validate/test_covalidity.ml b/src/proto_alpha/lib_protocol/test/integration/validate/test_covalidity.ml
index 8e266096c096f6fecb619d94dbab5f5fed17c9d9..c2fb1e2a55b936ffe26e35579eb652f933e8ea8e 100644
--- a/src/proto_alpha/lib_protocol/test/integration/validate/test_covalidity.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/validate/test_covalidity.ml
@@ -112,7 +112,7 @@ let covalid_permutation_and_bake ks nb_bootstrap =
           |> List.rev_filter is_not_preendorsement
         in
         (* Ensure that we can validate and apply this permutation *)
-        let* _b =
+        let* (_b : Block.t) =
           Block.bake ~allow_manager_failures:true state.block ~operations
         in
         loop (pred n)
diff --git a/src/proto_alpha/lib_protocol/test/integration/validate/test_manager_operation_validation.ml b/src/proto_alpha/lib_protocol/test/integration/validate/test_manager_operation_validation.ml
index 2d16cdda3096dbee56cbfc4219d686c705a65727..d5e81108f4266c0124aad7ff958ac9c2f9fbe038 100644
--- a/src/proto_alpha/lib_protocol/test/integration/validate/test_manager_operation_validation.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/validate/test_manager_operation_validation.ml
@@ -437,7 +437,7 @@ let test_validate infos kind =
       }
       infos
   in
-  let* _ = validate_diagnostic infos [op] in
+  let* (_ : infos) = validate_diagnostic infos [op] in
   return_unit
 
 (** Fee payment that emptying a self_delegated implicit. *)
@@ -457,7 +457,7 @@ let test_emptying_self_delegate infos kind =
       }
       infos
   in
-  let* _ = only_validate_diagnostic infos [op] in
+  let* (_ : infos) = only_validate_diagnostic infos [op] in
   return_unit
 
 (** Minimum gas cost to pass the validation:
@@ -484,7 +484,7 @@ let test_empty_undelegate infos kind =
       }
       infos
   in
-  let* _ = only_validate_diagnostic infos [op] in
+  let* (_ : infos) = only_validate_diagnostic infos [op] in
   return_unit
 
 (** No gas consumer with the minimal gas limit for manager operations
@@ -558,14 +558,11 @@ let test_feature_flags infos kind =
       infos
   in
   let flags = infos.flags in
-  let* () =
-    if is_disabled flags kind then
-      validate_ko_diagnostic infos [op] (flag_expect_failure flags)
-    else
-      let* _ = validate_diagnostic infos [op] in
-      return_unit
-  in
-  return_unit
+  if is_disabled flags kind then
+    validate_ko_diagnostic infos [op] (flag_expect_failure flags)
+  else
+    let* (_ : infos) = validate_diagnostic infos [op] in
+    return_unit
 
 let tests =
   let mk_default () = default_init_ctxt () in
diff --git a/src/proto_alpha/lib_protocol/test/integration/validate/test_validation_batch.ml b/src/proto_alpha/lib_protocol/test/integration/validate/test_validation_batch.ml
index 4709f1fffb5052631dde4f407d426ab3caa9447e..beff404e811fc454f8d59e9d81107089a4128f9f 100644
--- a/src/proto_alpha/lib_protocol/test/integration/validate/test_validation_batch.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/validate/test_validation_batch.ml
@@ -298,11 +298,21 @@ let batch_incons_counters infos kind1 kind2 =
           err
   in
   let* i = Incremental.begin_construction infos.ctxt.block in
-  let* _ = Incremental.add_operation ~expect_failure i batch_same in
-  let* _ = Incremental.add_operation ~expect_failure i batch_in_the_future in
-  let* _ = Incremental.add_operation ~expect_failure i batch_missing_one in
-  let* _ = Incremental.add_operation ~expect_failure i batch_inverse in
-  let* _ = Incremental.add_operation ~expect_failure i batch_in_the_past in
+  let* (_ : Incremental.t) =
+    Incremental.add_operation ~expect_failure i batch_same
+  in
+  let* (_ : Incremental.t) =
+    Incremental.add_operation ~expect_failure i batch_in_the_future
+  in
+  let* (_ : Incremental.t) =
+    Incremental.add_operation ~expect_failure i batch_missing_one
+  in
+  let* (_ : Incremental.t) =
+    Incremental.add_operation ~expect_failure i batch_inverse
+  in
+  let* (_ : Incremental.t) =
+    Incremental.add_operation ~expect_failure i batch_in_the_past
+  in
   return_unit
 
 (** A batch that consumes all the balance for fees can only face the total
@@ -361,7 +371,9 @@ let batch_emptying_balance_in_the_middle infos kind1 kind2 =
           Error_monad.pp_print_trace
           err
   in
-  let* _ = Incremental.add_operation i case1 ~expect_failure in
+  let* (_ : Incremental.t) =
+    Incremental.add_operation i case1 ~expect_failure
+  in
   return_unit
 
 (** A batch that consumes all the balance for fees only at the end of
@@ -417,8 +429,8 @@ let batch_empty_at_end infos kind1 kind2 =
       (Context.B infos.ctxt.block)
       [reveal; op_case2; op2_case2]
   in
-  let* _ = validate_diagnostic infos [case2] in
-  let* _ = validate_diagnostic infos [case3] in
+  let* (_ : infos) = validate_diagnostic infos [case2] in
+  let* (_ : infos) = validate_diagnostic infos [case3] in
   return_unit
 
 (** Simple reveal followed by a transaction. *)
@@ -454,8 +466,8 @@ let batch_reveal_transaction infos =
       (Context.B infos.ctxt.block)
       [reveal; transaction]
   in
-  let* _i = Incremental.begin_construction infos.ctxt.block in
-  let* _ = validate_diagnostic infos [batch] in
+  let* (_i : Incremental.t) = Incremental.begin_construction infos.ctxt.block in
+  let* (_ : infos) = validate_diagnostic infos [batch] in
   return_unit
 
 (** A batch of manager operation must not exceed the initial available gas in the block. *)
@@ -539,9 +551,15 @@ let batch_exceeding_block_gas ~mempool_mode infos kind1 kind2 =
           Error_monad.pp_print_trace
           err
   in
-  let* _ = Incremental.add_operation i case1 ~expect_failure in
-  let* _ = Incremental.add_operation i case3 ~expect_failure in
-  let* _ = Incremental.add_operation i case2 ~expect_failure in
+  let* (_ : Incremental.t) =
+    Incremental.add_operation i case1 ~expect_failure
+  in
+  let* (_ : Incremental.t) =
+    Incremental.add_operation i case3 ~expect_failure
+  in
+  let* (_ : Incremental.t) =
+    Incremental.add_operation i case2 ~expect_failure
+  in
   return_unit
 
 let make_tztest_batched ?(fmt = Format.std_formatter) name test subjects
diff --git a/src/proto_alpha/lib_protocol/test/integration/validate/validate_helpers.ml b/src/proto_alpha/lib_protocol/test/integration/validate/validate_helpers.ml
index 7c399cf014af490e0f4c52c9fac04fbe1166ecb1..9515b72cfa0950362cd1bbdf8770b0fe30b26580 100644
--- a/src/proto_alpha/lib_protocol/test/integration/validate/validate_helpers.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/validate/validate_helpers.ml
@@ -384,7 +384,7 @@ let delegates_of_block block =
 let sequential_validate ?(mempool_mode = true) block operations =
   let open Lwt_result_syntax in
   let* inc = Incremental.begin_construction ~mempool_mode block in
-  let* _inc =
+  let* (_inc : Incremental.t) =
     List.fold_left_es
       (fun acc op -> Incremental.validate_operation acc op)
       inc
diff --git a/src/proto_alpha/lib_protocol/test/pbt/liquidity_baking_pbt.ml b/src/proto_alpha/lib_protocol/test/pbt/liquidity_baking_pbt.ml
index f17af60c8e9a932c039d4b3f2ea16609ba87f2a7..5c38346b763fb3aad4b451ac0315778778f1c54a 100644
--- a/src/proto_alpha/lib_protocol/test/pbt/liquidity_baking_pbt.ml
+++ b/src/proto_alpha/lib_protocol/test/pbt/liquidity_baking_pbt.ml
@@ -244,7 +244,9 @@ let machine_validation_tests =
         extract_qcheck_tzresult
           (let invariant = validate_consistency in
            let* state, env = ValidationMachine.build ~invariant specs in
-           let* _ = ValidationMachine.run ~invariant scenario env state in
+           let* (_ : ValidationMachine.t) =
+             ValidationMachine.run ~invariant scenario env state
+           in
            return_unit));
     QCheck2.Test.make
       ~count:10
@@ -255,7 +257,9 @@ let machine_validation_tests =
         extract_qcheck_tzresult
           (let invariant = validate_storage in
            let* state, env = ConcreteMachine.build ~invariant specs in
-           let* _ = ConcreteMachine.run ~invariant scenario env state in
+           let* (_ : Block.t) =
+             ConcreteMachine.run ~invariant scenario env state
+           in
            return_unit));
     QCheck2.Test.make
       ~count:50_000
@@ -266,7 +270,9 @@ let machine_validation_tests =
         extract_qcheck_tzresult
           (let invariant = positive_pools in
            let state, env = SymbolicMachine.build ~invariant specs in
-           let _ = SymbolicMachine.run ~invariant scenario env state in
+           let (_ : SymbolicMachine.t) =
+             SymbolicMachine.run ~invariant scenario env state
+           in
            return_unit));
   ]
 
@@ -282,7 +288,7 @@ let economic_tests =
       (Liquidity_baking_generator.gen_adversary_scenario 1_000_000 1_000_000 50)
       (fun (specs, attacker, scenario) ->
         let state, env = SymbolicMachine.build ~subsidy:0L specs in
-        let _ =
+        let (_ : SymbolicMachine.t) =
           run_and_check (one_balance_decreases attacker env) scenario env state
         in
         true);
@@ -293,7 +299,7 @@ let economic_tests =
       (Liquidity_baking_generator.gen_scenario 1_000_000 1_000_000 50)
       (fun (specs, scenario) ->
         let state, env = SymbolicMachine.build ~subsidy:0L specs in
-        let _ =
+        let (_ : SymbolicMachine.t) =
           run_and_check (is_remove_liquidity_consistent env) scenario env state
         in
         true);
@@ -304,13 +310,13 @@ let economic_tests =
       (Liquidity_baking_generator.gen_scenario 1_000_000 1_000_000 50)
       (fun (specs, scenario) ->
         let state, env = SymbolicMachine.build ~subsidy:0L specs in
-        let _ =
+        let (_ : SymbolicMachine.t) =
           run_and_check (is_share_price_increasing env) scenario env state
         in
         true);
   ]
 
-let _ =
+let () =
   let open Lib_test.Qcheck2_helpers in
   Alcotest.run
     "protocol > pbt > liquidity baking"
diff --git a/src/proto_alpha/lib_protocol/test/pbt/test_carbonated_map.ml b/src/proto_alpha/lib_protocol/test/pbt/test_carbonated_map.ml
index 119cc368292d8ce8ab022a1de70c56f892927575..6e6e7f756f72588da8175601cd48aec908d38849 100644
--- a/src/proto_alpha/lib_protocol/test/pbt/test_carbonated_map.ml
+++ b/src/proto_alpha/lib_protocol/test/pbt/test_carbonated_map.ml
@@ -327,7 +327,7 @@ let test_find_existing =
   int_map_test "Find all elements" @@ fun map ->
   let ctxt = unsafe_new_context () in
   let* kvs, _ = CM.to_list ctxt map in
-  let* _ =
+  let* (_ : CM.context) =
     List.fold_left_e
       (fun ctxt (k, v) ->
         let* v_opt, ctxt = CM.find ctxt k map in
diff --git a/src/proto_alpha/lib_protocol/test/pbt/test_refutation_game.ml b/src/proto_alpha/lib_protocol/test/pbt/test_refutation_game.ml
index 0d2c865622190cd893f71933438c512572eb816e..e0439f6b085ee8cfae6347cee969f314da2f47d3 100644
--- a/src/proto_alpha/lib_protocol/test/pbt/test_refutation_game.ml
+++ b/src/proto_alpha/lib_protocol/test/pbt/test_refutation_game.ml
@@ -838,7 +838,7 @@ module Tree_inbox = struct
   let commit_tree store key tree =
     let open Lwt_syntax in
     let* store = Store.add_tree store key tree in
-    let* _ = Store.commit ~time:Time.Protocol.epoch store in
+    let* (_ : Context_hash.t) = Store.commit ~time:Time.Protocol.epoch store in
     return ()
 
   let lookup_tree store hash =
diff --git a/src/proto_alpha/lib_protocol/test/unit/test_alpha_context.ml b/src/proto_alpha/lib_protocol/test/unit/test_alpha_context.ml
index fd5af2672971057e40b25079e9aedd79fe4f7df4..77cda1e31232ffc04f3431891dab8d44bd2e72c8 100644
--- a/src/proto_alpha/lib_protocol/test/unit/test_alpha_context.ml
+++ b/src/proto_alpha/lib_protocol/test/unit/test_alpha_context.ml
@@ -238,7 +238,7 @@ module Test_Big_map = struct
     let* kvs1 = check_key_values ~loc:__LOC__ ~num_elements:20 () in
     let* kvs2 = check_key_values ~loc:__LOC__ ~num_elements:20 ~length:100 () in
     let* () = assert_equal_key_values ~loc:__LOC__ kvs1 kvs2 in
-    let* _ =
+    let* (_ : _ list) =
       check_key_values ~loc:__LOC__ ~num_elements:100 ~offset:100 ~length:1 ()
     in
     (* Offset greater than the length. *)
diff --git a/src/proto_alpha/lib_protocol/test/unit/test_bond_id_repr.ml b/src/proto_alpha/lib_protocol/test/unit/test_bond_id_repr.ml
index 86b65ecf2b934f0eed9b5041ad17b4d9eccf92e8..4d1a15287756e1016f514738c6ecabd23b9bbb2a 100644
--- a/src/proto_alpha/lib_protocol/test/unit/test_bond_id_repr.ml
+++ b/src/proto_alpha/lib_protocol/test/unit/test_bond_id_repr.ml
@@ -53,13 +53,13 @@ let test_destruct_sc_bond_id_repr () =
     | Some id -> Ok (Bond_id_repr.Sc_rollup_bond_id id)
     | None -> Error "Not an sc address"
   in
-  let* _ =
+  let* () =
     assert_bond_id_result_equal
       ~loc:__LOC__
       (destruct sc_rollup_address1)
       (sc_bond sc_rollup_address1)
   in
-  let* _ =
+  let* () =
     assert_bond_id_result_equal
       ~loc:__LOC__
       (destruct sc_rollup_address2)
@@ -80,13 +80,13 @@ let test_destruct_tx_bond_id_repr () =
     | Some id -> Ok (Bond_id_repr.Tx_rollup_bond_id id)
     | None -> Error "Not a tx address"
   in
-  let* _ =
+  let* () =
     assert_bond_id_result_equal
       ~loc:__LOC__
       (destruct tx_rollup_address1)
       (tx_bond tx_rollup_address1)
   in
-  let* _ =
+  let* () =
     assert_bond_id_result_equal
       ~loc:__LOC__
       (destruct tx_rollup_address2)
@@ -101,7 +101,7 @@ let test_destruct_invalid_bond_id_repr () =
   let invalid_address = "asdfasdfasdf" in
   let empty_address = "" in
   let destruct = Bond_id_repr.Internal_for_test.destruct in
-  let* _ =
+  let* () =
     Assert.is_error ~loc:__LOC__ ~pp:Bond_id_repr.pp (destruct invalid_address)
   in
   Assert.is_error ~loc:__LOC__ ~pp:Bond_id_repr.pp (destruct empty_address)
@@ -124,9 +124,9 @@ let test_roundtrip () =
   let tx_rollup_address2 = "txr1YNMEtkj5Vkqsbdmt7xaxBTMRZjzS96UAi" in
   let sc_rollup_address1 = "scr1HLXM32GacPNDrhHDLAssZG88eWqCUbyLF" in
   let sc_rollup_address2 = "scr1Ew52VCdi6nF1JuokRGMqfmSeiAEXymW2m" in
-  let* _ = rountrip_test __LOC__ tx_rollup_address1 in
-  let* _ = rountrip_test __LOC__ tx_rollup_address2 in
-  let* _ = rountrip_test __LOC__ sc_rollup_address1 in
+  let* () = rountrip_test __LOC__ tx_rollup_address1 in
+  let* () = rountrip_test __LOC__ tx_rollup_address2 in
+  let* () = rountrip_test __LOC__ sc_rollup_address1 in
   rountrip_test __LOC__ sc_rollup_address2
 
 let tests =
diff --git a/src/proto_alpha/lib_protocol/test/unit/test_dal_slot_proof.ml b/src/proto_alpha/lib_protocol/test/unit/test_dal_slot_proof.ml
index fff2e8efbe5f26f24f2a4b79cd7da36c352d8d9f..d14a7f9035027e6d242fc48cbaaee2c4cd606f6e 100644
--- a/src/proto_alpha/lib_protocol/test/unit/test_dal_slot_proof.ml
+++ b/src/proto_alpha/lib_protocol/test/unit/test_dal_slot_proof.ml
@@ -88,7 +88,7 @@ struct
       ~mk_level:(fun id -> Raw_level_repr.succ id.H.published_level)
       ~mk_slot_index:(fun id -> id.H.index)
       ~check_result:(fun res ->
-        let* _skip_list = Assert.get_ok ~__LOC__ res in
+        let* (_skip_list : Hist.t) = Assert.get_ok ~__LOC__ res in
         return_unit)
 
   (** This test attempts to add a slot on top of genesis cell zero which satisfies
@@ -100,7 +100,7 @@ struct
       ~mk_level:(fun id -> id.H.published_level)
       ~mk_slot_index:(fun id -> succ_slot_index id.H.index)
       ~check_result:(fun res ->
-        let* _skip_list = Assert.get_ok ~__LOC__ res in
+        let* (_skip_list : Hist.t) = Assert.get_ok ~__LOC__ res in
         return_unit)
 
   (** This test attempts to add two slots on top of genesis cell zero which satisfies
@@ -119,7 +119,7 @@ struct
             Raw_level_repr.(succ (succ id.H.published_level)))
           ~mk_slot_index:(fun id -> id.H.index)
           ~check_result:(fun res ->
-            let* _skip_list = Assert.get_ok ~__LOC__ res in
+            let* (_skip_list : Hist.t) = Assert.get_ok ~__LOC__ res in
             return_unit))
 
   (* Tests of construct/verify proofs that confirm/unconfirm pages on top of
diff --git a/src/proto_alpha/lib_protocol/test/unit/test_merkle_list.ml b/src/proto_alpha/lib_protocol/test/unit/test_merkle_list.ml
index 207692cf643b2ae3536701193ee84e5b2a113799..af2b1149f73677eef95e3b373dc4a0bf60844da2 100644
--- a/src/proto_alpha/lib_protocol/test/unit/test_merkle_list.ml
+++ b/src/proto_alpha/lib_protocol/test/unit/test_merkle_list.ml
@@ -149,14 +149,12 @@ let test_check_path () =
   in
   let elements_array = Array.of_list elements in
   let t = List.fold_left snoc_tr nil elements in
-  let _ =
-    Stdlib.List.init n (fun pos ->
-        let* path = compute_path t pos in
-        let* b = check_path path pos elements_array.(pos) (ML.root t) in
-        assert b ;
-        return_unit)
-  in
-  return_unit
+  Stdlib.List.init n (fun pos ->
+      let* path = compute_path t pos in
+      let* b = check_path path pos elements_array.(pos) (ML.root t) in
+      assert b ;
+      return_unit)
+  |> Environment.Error_monad.Tzresult_syntax.join
 
 (* Check that a path is only valid for the position for which it
    was computed *)
@@ -169,13 +167,11 @@ let test_check_path_wrong_pos () =
   let elements_array = Array.of_list elements in
   let t = List.fold_left snoc_tr ML.nil elements in
   let* path = compute_path t (n - 1) in
-  let _ =
-    Stdlib.List.init (n - 2) (fun pos ->
-        let* b = check_path path pos elements_array.(pos) (ML.root t) in
-        assert (not b) ;
-        return_unit)
-  in
-  return_unit
+  Stdlib.List.init (n - 2) (fun pos ->
+      let* b = check_path path pos elements_array.(pos) (ML.root t) in
+      assert (not b) ;
+      return_unit)
+  |> Environment.Error_monad.Tzresult_syntax.join
 
 (* Check that a computed path is invalidated by a tree update  *)
 let test_check_invalidated_path () =
diff --git a/src/proto_alpha/lib_protocol/test/unit/test_raw_level_repr.ml b/src/proto_alpha/lib_protocol/test/unit/test_raw_level_repr.ml
index 9543efcdf22e1785e1b476afc9fe9026ae2d829f..4f12f21eba1d2357c2f495c2add57935de44cf10 100644
--- a/src/proto_alpha/lib_protocol/test/unit/test_raw_level_repr.ml
+++ b/src/proto_alpha/lib_protocol/test/unit/test_raw_level_repr.ml
@@ -84,7 +84,7 @@ module Test_raw_level_repr = struct
      | Error _ -> return_unit)
     >>=? fun () ->
     try
-      let _ = Raw_level_repr.of_int32_exn int32v in
+      let (_ : Raw_level_repr.t) = Raw_level_repr.of_int32_exn int32v in
       failwith "Negative int32s should not be coerced into raw_level"
     with Invalid_argument _ -> return_unit
 
diff --git a/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_arith.ml b/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_arith.ml
index 61ad98d29a117c170967bfbb9db5ec865128e6b0..4f49832e6e8eca6524547250d3088a52f891cbb4 100644
--- a/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_arith.ml
+++ b/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_arith.ml
@@ -81,7 +81,9 @@ module Arith_Context = struct
     (* FIXME: With on-disk context, we cannot commit the empty
        context. Is it also true in our case? *)
     let* context = Context_binary.add_tree context [] tree in
-    let* _hash = Context_binary.commit ~time:Time.Protocol.epoch context in
+    let* (_hash : Context_hash.t) =
+      Context_binary.commit ~time:Time.Protocol.epoch context
+    in
     let index = Context_binary.index context in
     match Context_binary.Tree.kinded_key tree with
     | Some k ->
diff --git a/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_inbox.ml b/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_inbox.ml
index d7289e4e6168e06312f86edd1a6db4d21a0f9c0c..fbcf756c65049202bad1aa1f175c590b39f4ffea 100644
--- a/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_inbox.ml
+++ b/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_inbox.ml
@@ -220,7 +220,7 @@ module Tree = struct
   let commit_tree context key tree =
     let open Lwt_syntax in
     let* ctxt = Tezos_context_memory.Context.add_tree context key tree in
-    let* _ = commit ~time:Time.Protocol.epoch ~message:"" ctxt in
+    let* (_ : value_key) = commit ~time:Time.Protocol.epoch ~message:"" ctxt in
     return ()
 
   let lookup_tree context hash =
diff --git a/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_storage.ml b/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_storage.ml
index 4187fc86380d765a805c8aade5d00cc1ed411a31..720132968a8d447b886a3fcad95ee467aba214c1 100644
--- a/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_storage.ml
+++ b/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_storage.ml
@@ -2478,7 +2478,7 @@ let test_limit_on_number_of_messages_during_commitment_period with_gap () =
   in
   if with_gap then
     (* Changing the commitment period is enough to accept that many messages... *)
-    let*? _r = add_too_many_messages in
+    let*? (_r : Raw_context.t) = add_too_many_messages in
     return ()
   else
     (* ... but if we stay in the same commitment period, it fails. *)
diff --git a/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_wasm.ml b/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_wasm.ml
index 31e6bdaba3caa19be7f66976a99f2ed0407e1efe..41bc79f67c51cd5bb2b2dd2ff1618601811ede56 100644
--- a/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_wasm.ml
+++ b/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_wasm.ml
@@ -66,7 +66,9 @@ module Wasm_context = struct
   let produce_proof context tree step =
     let open Lwt_syntax in
     let* context = Context.add_tree context [] tree in
-    let* _hash = Context.commit ~time:Time.Protocol.epoch context in
+    let* (_hash : Context_hash.t) =
+      Context.commit ~time:Time.Protocol.epoch context
+    in
     let index = Context.index context in
     match Context.Tree.kinded_key tree with
     | Some k ->
diff --git a/src/proto_alpha/lib_protocol/test/unit/test_tez_repr.ml b/src/proto_alpha/lib_protocol/test/unit/test_tez_repr.ml
index 6d94465845d65bc7da65a7d6602883a63a5caa10..9367d4a9a088ec59ebfb80cf759c092ee1a11009 100644
--- a/src/proto_alpha/lib_protocol/test/unit/test_tez_repr.ml
+++ b/src/proto_alpha/lib_protocol/test/unit/test_tez_repr.ml
@@ -126,7 +126,7 @@ module Test_tez_repr = struct
 
   let test_of_mutez_exn_negative () =
     try
-      let _ = Tez_repr.of_mutez_exn (-1000000L) in
+      let (_ : Tez_repr.t) = Tez_repr.of_mutez_exn (-1000000L) in
       failwith "should have failed to converted -1000000L to tez"
     with
     | Invalid_argument _ -> return_unit
diff --git a/src/proto_alpha/lib_protocol/test/unit/test_tx_rollup_l2.ml b/src/proto_alpha/lib_protocol/test/unit/test_tx_rollup_l2.ml
index b95ed7e35c17d1ff47b3017a1adc9c28cd0434f6..f0fd2133a596c16a529b82aa181cf9be7e6abe5a 100644
--- a/src/proto_alpha/lib_protocol/test/unit/test_tx_rollup_l2.ml
+++ b/src/proto_alpha/lib_protocol/test/unit/test_tx_rollup_l2.ml
@@ -402,15 +402,13 @@ module Test_Ticket_ledger = struct
       to an address. *)
   let test_credit_unknown_index () =
     let ctxt = empty_context in
-
-    let* _ctxt =
+    let* (_ctxt : t) =
       credit
         ctxt
         ticket_idx1
         (Indexable.index_exn 0l)
         (Tx_rollup_l2_qty.of_int64_exn 1L)
     in
-
     return_unit
 
   (** Test that spending a ticket from an index to another one behaves correctly *)