diff --git a/test/extensions_test.ml b/test/extensions_test.ml
index 63b2fd7c..806eba03 100644
--- a/test/extensions_test.ml
+++ b/test/extensions_test.ml
@@ -16,6 +16,7 @@ let%expect_test _ =
   let foo = Extensions.Foo.{ bar = Some 5; extensions' = Ocaml_protoc_plugin.Extensions.default } in
   let foo = Extensions.Baz'.set foo (Some 8) in
   let foo = Extensions.Baz'.set foo (Some 7) in
+  Test_lib.test_encode ~protoc:false (module Extensions.Foo) foo;
   let baz = Extensions.Baz'.get foo in
   print_endline ([%show: Extensions.Foo.t] foo);
   print_endline ([%show: Extensions.Baz.t Ocaml_protoc_plugin.Result.t] baz);
@@ -34,6 +35,8 @@ let%expect_test _ =
   let foo = Extensions.Baz'.set foo (Some 0) in
   let foo = Extensions.B2.set foo ([6;7;8]) in
   let foo = Extensions.B2.set foo ([]) in
+  Test_lib.test_encode ~protoc:false (module Extensions.Foo) foo;
+
   print_endline ([%show: Extensions.Foo.t] foo);
   ();
   [%expect {|
@@ -42,6 +45,8 @@ let%expect_test _ =
 let%expect_test _ =
   let foo = Extensions.Foo.{ bar = Some 5; extensions' = Ocaml_protoc_plugin.Extensions.default } in
   let foo = Extensions.Baz'.set foo (Some 7) in
+  Test_lib.test_encode ~protoc:false (module Extensions.Foo) foo;
+
   let foo' =
     Extensions.Foo.to_proto foo
     |> Ocaml_protoc_plugin.Writer.contents
@@ -61,6 +66,7 @@ let%expect_test _ =
 let%expect_test _ =
   let v = [6;7;8;9] in
   let foo = Extensions.Foo.{ bar = Some 5; extensions' = Ocaml_protoc_plugin.Extensions.default } in
+  Test_lib.test_encode ~protoc:false (module Extensions.Foo) foo;
   let foo = Extensions.R_baz.set foo v in
   let foo' =
     Extensions.Foo.to_proto foo
@@ -100,6 +106,7 @@ let%expect_test _ =
 
   let foo = Extensions.B.set foo 0 in
   Printf.printf "Set B = 0: %d\n" (Extensions.B.get foo |> Ocaml_protoc_plugin.Result.get ~msg:"No Value");
+  Test_lib.test_encode ~protoc:false (module Extensions.Foo) foo;
   print_endline ([%show: Extensions.Foo.t] foo);
   ();
   [%expect {|
diff --git a/test/large_test.ml b/test/large_test.ml
index d9b82437..d1185f12 100644
--- a/test/large_test.ml
+++ b/test/large_test.ml
@@ -1,19 +1,8 @@
 open Large
-open Ocaml_protoc_plugin
 
 let%expect_test "Test very large message type" =
   let large = Large.make ~x7:7 () in
-  let writer = Large.to_proto large in
-  let contents = Writer.contents writer in
-  Printf.printf "Size of large message: %d\n" (String.length contents);
-  let reader = Reader.create contents in
-  let large' = Large.from_proto_exn reader in
-  Printf.printf "Serialization works: %b\n" (large = large');
-  Printf.printf "x7: %d = %d\n" large.x7 large'.x7;
-  Printf.printf "x5: %d = %d\n" large.x5 large'.x5;
+  Test_lib.test_encode (module Large) large;
   ();
   [%expect {|
-    Size of large message: 2
-    Serialization works: true
-    x7: 7 = 7
-    x5: 0 = 0 |}]
+    x7: 7 |}]
diff --git a/test/merge_test.ml b/test/merge_test.ml
index 8f28e3b0..ef439fab 100644
--- a/test/merge_test.ml
+++ b/test/merge_test.ml
@@ -3,7 +3,6 @@ open Merge.Merge
 
 let test_merge (type t) (module T: Test_lib.T with type t = t) (init : t) (ts: t list) =
   let open Ocaml_protoc_plugin in
-
   let writer = Writer.init () in
   let expect =
     List.fold_left ~init ~f:(fun acc t ->
diff --git a/test/primitive_types_test.ml b/test/primitive_types_test.ml
index d1754183..b9acf60c 100644
--- a/test/primitive_types_test.ml
+++ b/test/primitive_types_test.ml
@@ -42,26 +42,8 @@ let%expect_test _ =
 
 let%expect_test _ =
   let module T = Primitive_types.Types in
-  let t =
-    T.
-      {
-        int64 = 0;
-        sint64 = 0;
-        uint64 = 0;
-        int32 = 0;
-        sint32 = 0;
-        uint32 = 0;
-        double = 0.0;
-        float = 0.0;
-        fixed64 = 0L;
-        fixed32 = 0l;
-        sfixed64 = 0L;
-        sfixed32 = 0l;
-        bool = false;
-        string = "";
-        bytes = Bytes.of_string "";
-      }
-  in
+  let t = T.make () in
+  Test_lib.test_encode (module T) t;
   let bin = T.to_proto t in
   Printf.printf "Size: %d%!" (Ocaml_protoc_plugin.Writer.contents bin |> String.length);
   [%expect {| Size: 0 |}]
diff --git a/test/proto2.proto b/test/proto2.proto
index fa046fd7..95e64dd3 100644
--- a/test/proto2.proto
+++ b/test/proto2.proto
@@ -9,6 +9,7 @@ message A {
 message Message {
   message Required {
     optional uint64 a = 1;
+    optional uint64 b = 2;
   }
   enum E {
     A = 0;
diff --git a/test/proto2_test.ml b/test/proto2_test.ml
index 3be69b0c..5f2b8b67 100644
--- a/test/proto2_test.ml
+++ b/test/proto2_test.ml
@@ -1,7 +1,12 @@
 open Proto2
+
 let%expect_test _ =
   let module T = Proto2.Message in
-  let t = T.{enum = Some E.B; i = 0; j = 5; required = Some 7; k = Some 5 } in
+  (* Verify signature that required messages are mapped as mandatory arguments *)
+  let make: ?enum:T.E.t -> ?i:int -> j:int -> required:T.Required.t -> ?k:int -> unit -> T.t = T.make in
+  let t' = make ~enum:T.E.B ~i:0 ~j:5 ~required:(T.Required.make ~a:7 ()) ~k:5 () in
+  let t = T.{enum = Some E.B; i = 0; j = 5; required = T.Required.make ~a:7 (); k = Some 5 } in
+  if (not (T.equal t t')) then Printf.eprintf "Error: Type does not match";
   Test_lib.test_encode (module T) t;
   [%expect {|
     enum: B