test(clerk): add minimal unit testing structure

build_system/ninja_utils.ml

@@ -11,7 +11,7 @@ module Expr = struct
   let rec to_string = function
     | Lit s -> s
     | Var s -> "$" ^ s
-    | Seq ls -> List.fold_left (fun acc s -> acc ^ " " ^ to_string s) "" ls
+    | Seq ls -> List.fold_left (fun acc s -> acc ^ " " ^ to_string s) " " ls
 
   let list_to_string ?(sep = " ") ls = ls |> List.map to_string |> String.concat sep
 end
@@ -46,13 +46,15 @@ module Build = struct
   let make_with_inputs ~outputs ~rule ~inputs =
     { outputs; rule; inputs = Option.some inputs; vars = [] }
 
+  let empty = make ~outputs:[ Expr.Lit "empty" ] ~rule:"phony"
+
   (** [unpath path] replaces all '/' occurences with '-' in [path] to avoid ninja writing the
       corresponding file. *)
   let unpath path = Re.Pcre.(substitute ~rex:(regexp "/") ~subst:(fun _ -> "-")) path
 
   let to_string build =
     Printf.sprintf "build %s: %s" (Expr.list_to_string build.outputs) build.rule
-    ^ (build.inputs |> Option.fold ~some:(fun ls -> Expr.list_to_string ls) ~none:"")
+    ^ (build.inputs |> Option.fold ~some:(fun ls -> " " ^ Expr.list_to_string ls) ~none:"")
     ^ "\n"
     ^ List.fold_left
         (fun acc (name, exp) -> acc ^ Printf.sprintf "  %s = %s\n" name (Expr.to_string exp))

build_system/ninja_utils.mli

@@ -36,6 +36,9 @@ module Build : sig
 
   val make_with_inputs : outputs:Expr.t list -> rule:string -> inputs:Expr.t list -> t
 
+  val empty : t
+  (** [empty] is the minimal ninja build. *)
+
   val unpath : string -> string
   (** [unpath path] replaces all '/' occurences with '-' in [path] to avoid ninja writing the
       corresponding file. *)

build_system/test/dune

@@ -0,0 +1,5 @@
+(dirs ..)
+
+(tests
+  (names ninja_utils)
+  (libraries alcotest ninja_utils))

build_system/test/ninja_utils.ml

@@ -0,0 +1,27 @@
+open Alcotest
+open Ninja_utils
+module B = Build
+module E = Expr
+
+module To_test = struct
+  let build_to_string = B.to_string
+end
+
+let test_empty_build () =
+  check string "Must be the same string" "build empty: phony\n" (To_test.build_to_string B.empty)
+
+let test_empty_build_w_inputs () =
+  check string "Must be the same string" "build output: rule in1 in2\n"
+    (To_test.build_to_string
+       (B.make_with_inputs ~outputs:[ E.Lit "output" ] ~rule:"rule"
+          ~inputs:[ E.Lit "in1"; E.Lit "in2" ]))
+
+let () =
+  run "Ninja builds"
+    [
+      ( "to_string",
+        [
+          test_case "Empty build" `Quick test_empty_build;
+          test_case "Empty build \\w inputs" `Quick test_empty_build_w_inputs;
+        ] );
+    ]