Add note about justfile in readme

.gitignore

@@ -0,0 +1,2 @@
+_build/
+_coverage/

.ocamlformat

@@ -0,0 +1,2 @@
+version=0.26.1
+profile=default

Justfile

@@ -0,0 +1,10 @@
+build:
+	@dune build
+
+test:
+	@dune test -f
+	@bisect-ppx-report html
+	@bisect-ppx-report summary --per-file
+
+fmt:
+	@dune build @fmt --auto-promote

README.md

@@ -40,6 +40,13 @@ watch_file **/*.nix
 use flake_env .
 ```
 
+## Developing
+
+This repo uses [just](https://just.systems/) to manage simple build jobs.
+After activating the development environment in the repo, run `just -l`  to list tasks.
+
+Please remember to format code before issuing patches.
+
 ## Credits
 
 This takes huge inspiration (and literal code-chunks) from nix-direnv. 

bin/dune

@@ -1,5 +1,14 @@
 (executable
  (name flake_env)
  (public_name flake_env)
-  (libraries core core_unix core_unix.filename_unix core_unix.sys_unix ppx_yojson_conv re sha lib)
+ (libraries
-  (preprocess (pps ppx_yojson_conv ppx_jane)))
+  core
+  core_unix
+  core_unix.filename_unix
+  core_unix.sys_unix
+  ppx_yojson_conv
+  re
+  sha
+  lib)
+ (preprocess
+  (pps ppx_yojson_conv ppx_jane)))

bin/flake_env.re

@@ -1,149 +1,57 @@
 open Core;
 module Unix = Core_unix;
 
+open Lib;
 
-let preflight = (layout_directory) => {
-  switch (Lib.Versions.preflight_versions(), Sys_unix.is_directory(layout_directory)) {
-    | (Ok(_), `Yes) => Ok()
-    | (Ok(_), _) => {
-      Unix.mkdir_p(layout_directory);
-      Ok()
-    }
-    | (err, _) => err
-  }
-}
-
-let hash_files = (filenames) => {
-  let ctx = Sha1.init();
-  let () = filenames
-  |> Array.filter(~f=f => switch (Sys_unix.file_exists(f)) {
-      | `Yes => true
-      | _ => false
-    })
-  |> Array.iter(~f=(f) => {
-    f |> In_channel.create |> In_channel.input_all |> Sha1.update_string(ctx);
-  });
-  Sha1.finalize(ctx) |> Sha1.to_hex
-};
-
-// TODO: Maybe make this more terse?
-let rec rmrf = (path) => {
-  switch (Unix.lstat(path).st_kind) {
-  | exception Unix.Unix_error(_, _, _) => ()
-  | S_REG => Unix.unlink(path)
-  | S_LNK => Unix.unlink(path)
-  | S_DIR => {
-      Sys_unix.readdir(path) |> Array.iter(~f=name => rmrf(Filename.concat(path, name)));
-      Unix.rmdir(path)
-    }
-  | S_CHR => Printf.eprintf("Don't know how to handle Character Device file\n")
-  | S_BLK => Printf.eprintf("Don't know how to handle Block Device file\n")
-  | S_FIFO => Printf.eprintf("Don't know how to handle FIFO file\n")
-  | S_SOCK => Printf.eprintf("Don't know how to handle Socket file\n")
-  }
-};
-
-let clean_old_gcroots = (layout_dir) => {
-  rmrf(layout_dir ++ "/flake-inputs/");
-  rmrf(layout_dir);
-  Unix.mkdir_p(layout_dir ++ "/flake-inputs/");
-};
-
-let print_cur_cache = (profile_rc) => {
-  In_channel.read_all(profile_rc) |> Printf.printf("%s")
-};
-
-let add_gcroot = (store_path, symlink) => {
-  switch (Lib.Util.nix(["build", "--out-link", symlink, store_path])) {
-  | (Ok(), _) => Ok()
-  | (err, _) => err
-  }
-}
-
-let freshen_cache = (layout_dir, hash, flake_specifier) => {
-  clean_old_gcroots(layout_dir);
-  let tmp_profile = layout_dir ++ "flake-tmp-profile."  ++ Core.Pid.to_string(Core_unix.getpid());
-  let (exit_code, stdout_content) = Lib.Util.nix(["print-dev-env", "--profile", tmp_profile, flake_specifier]);
-
-  let profile = layout_dir ++ "/flake-profile-" ++ hash;
-  let profile_rc = profile ++ ".rc";
-
-  switch (exit_code) {
-  | Ok() => {
-      Out_channel.with_file(~f=f=> Out_channel.output_string(f, stdout_content), profile_rc);
-      switch (add_gcroot(tmp_profile, profile)) {
-        | Ok() => {
-          Sys_unix.remove(tmp_profile);
-          let flake_input_cache_path = layout_dir ++ "/flake-inputs/"
-          let flake_inputs = Lib.Watches.get_input_paths();
-          flake_inputs |> List.iter(~f=(inpt) => {
-            switch (add_gcroot("/nix/store/" ++ inpt, flake_input_cache_path ++ inpt)) {
-            | Ok() => ()
-            | err => Printf.eprintf("Failed creating flake-input gcroot: %s\n", Core_unix.Exit_or_signal.to_string_hum(err));
-            };
-          });
-          print_cur_cache(profile_rc);
-        }
-        | err => {
-          Printf.eprintf("Failed creating gcroot: %s\n", Core_unix.Exit_or_signal.to_string_hum(err));
-          exit(1);
-        }
-      };
-    }
-  | err => {
-      Printf.eprintf("Failed evaluating flake: %s\n", Core_unix.Exit_or_signal.to_string_hum(err));
-      exit(1);
-    }
-  };
-
-};
-
-// TODO: Extend to add support for additional flags, maybe?
 let main = () => {
   let argv = Sys.get_argv();
-  switch (Array.length(argv)) {
+  switch (Util.get_args(argv)) {
-  | 3 => {
+  | Ok((layout_directory, flake_specifier, other_args)) =>
-      let flake_specifier = argv[1];
-      let layout_directory = argv[2];
     switch (preflight(layout_directory)) {
-        | Ok() => {
+    | Ok () =>
       switch (Lib.Watches.get()) {
-            | Ok(watches) => {
+      | Ok(watches) =>
         let paths = Array.map(~f=watch => watch.path, watches);
-                let hash = hash_files(paths);
+        let hash = Util.hash_files(paths);
         let profile = layout_directory ++ "/flake-profile-" ++ hash;
         let profile_rc = profile ++ ".rc";
 
-                switch ((Sys_unix.is_file(profile_rc), Sys_unix.is_file(profile))) {
+        switch (Sys_unix.is_file(profile_rc), Sys_unix.is_file(profile)) {
-                | (`Yes, `Yes) => {
+        | (`Yes, `Yes) =>
           let profile_rc_mtime = Unix.stat(profile_rc).st_mtime;
-                    let all_older= Array.map(~f=watch => watch.modtime, watches)
+          let all_older =
-                    |> Array.for_all(~f=watch_mtime => watch_mtime <= int_of_float(profile_rc_mtime))
+            Array.map(~f=watch => watch.modtime, watches)
-                    switch (all_older) {
+            |> Array.for_all(~f=watch_mtime =>
-                    | true => print_cur_cache(profile_rc)
+                 watch_mtime <= int_of_float(profile_rc_mtime)
-                    | false => freshen_cache(layout_directory, hash, flake_specifier)
+               );
-                    }
+          if (all_older) {
-                  }
+            print_cur_cache(profile_rc);
-                | _ => freshen_cache(layout_directory, hash, flake_specifier)
+          } else {
-                }
+            freshen_cache(
+              layout_directory,
+              hash,
+              flake_specifier,
+              other_args,
+            );
           };
-            | Error(e) => {
+        | _ =>
+          freshen_cache(layout_directory, hash, flake_specifier, other_args)
+        };
+      | Error(e) =>
         Printf.eprintf("%s\n", e);
         exit(1);
       }
-            }
+    | Error(e) =>
-          }
-      | Error(e) => {
       Printf.eprintf("%s\n", e);
       exit(1);
     }
-      };
+  | Error () =>
-    }
+    Printf.eprintf(
-  | _ => {
+      "%s  <layout_directory> <flake specifier> <...args>\n",
-      Printf.eprintf("%s <flake specifier> <layout_directory>\n", argv[0]);
+      argv[0],
+    );
     exit(1);
-      }
+  };
-  }
+};
-}
 
 let () = main();

direnvrc

@@ -41,7 +41,7 @@ use_flake_env() {
   local ld=$(direnv_layout_dir)
   export direnv
 
-  eval "$(@flake_env@ "$1" "$ld")"
+  eval "$(@flake_env@ "$ld" "$@")"
 
   export -n direnv
 

dune-project

@@ -1,18 +1,11 @@
-(lang dune 3.11)
+(lang dune 3.12)
 
 (name flake_env)
-
 (generate_opam_files true)
-
+(source (sourcehut bryan_bennett/flake_env))
-(source
- (sourcehut bryan_bennett/flake_env))
-
 (authors "Bryan Bennett")
-
 (maintainers "Bryan Bennett")
-
 (license MIT)
-
 (documentation https://git.sr.ht/~bryan_bennett/flake_env)
 
 (package

dune-workspace

@@ -0,0 +1,2 @@
+(lang dune 3.12)
+(instrument_with bisect_ppx)

flake.nix

@@ -29,6 +29,9 @@
           devShells.default = pkgs.mkShell {
             inputsFrom = [ self'.packages.default ];
             packages = [
+              pkgs.just
+              pkgs.ocamlPackages.alcotest
+              pkgs.ocamlPackages.bisect_ppx
               pkgs.ocamlPackages.dune_3
               pkgs.ocamlPackages.findlib
               pkgs.ocamlPackages.ocaml

flake_env.opam

@@ -10,7 +10,7 @@ doc: "https://git.sr.ht/~bryan_bennett/flake_env"
 bug-reports: "https://todo.sr.ht/~bryan_bennett/flake_env"
 depends: [
   "ocaml"
-  "dune" {>= "3.11"}
+  "dune" {>= "3.12"}
   "odoc" {with-doc}
 ]
 build: [

lib/dune

@@ -1,5 +1,15 @@
 (library
  (name lib)
  (public_name flake_env.lib)
-  (libraries core core_unix core_unix.filename_unix core_unix.sys_unix ppx_yojson_conv re sha)
+ (libraries
-  (preprocess (pps ppx_yojson_conv ppx_jane ppx_inline_test)))
+  core
+  core_unix
+  core_unix.filename_unix
+  core_unix.sys_unix
+  ppx_yojson_conv
+  re
+  sha)
+ (instrumentation
+  (backend bisect_ppx))
+ (preprocess
+  (pps ppx_yojson_conv ppx_jane)))

lib/flake_env__util.re

@@ -1,10 +1,64 @@
 open Core;
 module Unix = Core_unix;
 
-let nix = (args) => {
+let run_process = (name, args) => {
-  let stdout_chan = Unix.open_process_in(
+  /*** Run a process [name] with args [args], returning (exit_code, stdout text) */
-    "nix --extra-experimental-features \"nix-command flakes\" " ++ (args |> String.concat(~sep=" ")));
+  let stdout_chan =
+    Unix.open_process_in(name ++ " " ++ (args |> String.concat(~sep=" ")));
   let stdout_content = stdout_chan |> In_channel.input_all;
   let exit_code = Unix.close_process_in(stdout_chan);
-  (exit_code, stdout_content)
+  (exit_code, stdout_content);
-}
+};
+
+let nix = args =>
+  run_process(
+    "nix",
+    ["--extra-experimental-features", "\"nix-command flakes\" ", ...args],
+  );
+
+let hash_files = filenames => {
+  /*** Hash all entries in [filenames], returning a hex-encoded string of the hash of their contents */
+  let ctx = Sha1.init();
+  let () =
+    filenames
+    |> Array.filter(~f=f =>
+         switch (Sys_unix.file_exists(f)) {
+         | `Yes => true
+         | _ => false
+         }
+       )
+    |> Array.iter(~f=f => {
+         f
+         |> In_channel.create
+         |> In_channel.input_all
+         |> Sha1.update_string(ctx)
+       });
+  Sha1.finalize(ctx) |> Sha1.to_hex;
+};
+
+let rec rmrf = path => {
+  switch (Unix.lstat(path).st_kind) {
+  | exception (Unix.Unix_error(_, _, _)) => ()
+  | S_REG
+  | S_LNK => Unix.unlink(path)
+  | S_DIR =>
+    Sys_unix.readdir(path)
+    |> Array.iter(~f=name => rmrf(Filename.concat(path, name)));
+    Unix.rmdir(path);
+  | _ =>
+    Printf.eprintf(
+      "Unsupported file type (Chr or Block device, FIFO, or Socket)\n",
+    )
+  };
+};
+
+let get_args = argv => {
+  switch (Array.length(argv)) {
+  | x when x >= 3 =>
+    let layout_directory = argv[1];
+    let flake_specifier = argv[2];
+    let other_args = snd(List.split_n(List.of_array(argv), 3));
+    Ok((layout_directory, flake_specifier, other_args));
+  | _ => Error()
+  };
+};

lib/flake_env__versions.re

@@ -1,82 +1,84 @@
 open Core;
 module Unix = Core_unix;
 
+module Util = Flake_env__util;
+
 type t = {
   major: int,
   minor: int,
   point: int,
 };
 
+let init = (major, minor, point) => {major, minor, point};
+
+let required_direnv_version = init(2, 21, 3);
+
+let required_nix_version = init(2, 10, 0);
+
 let semver_re = Re.compile(Re.Posix.re({|([0-9]+)\.([0-9]+)\.([0-9]+)|}));
 
-let required_direnv_version = {
+let compare = (a, b) => {
-  major: 2,
-  minor: 21,
-  point: 3
-};
-
-let required_nix_version = {
-  major: 2,
-  minor: 10,
-  point: 0
-};
-
-// TODO: test this
-let compare_version_number = (a, b) => {
   switch (a, b) {
   | (a, b) when a.major == b.major && a.minor == b.minor && a.point == b.point => 0
-  | (a, b) when a.major < b.major => -1
+  | (a, b) when a.major < b.major => (-1)
-  | (a, b) when a.major == b.major && a.minor < b.minor => -1
+  | (a, b) when a.major == b.major && a.minor < b.minor => (-1)
-  | (a, b) when a.major == b.major && a.minor == b.minor && a.point < b.point => -1
+  | (a, b) when a.major == b.major && a.minor == b.minor && a.point < b.point => (-1)
   | _ => 1
-  }
+  };
-}
+};
 
-let%test_unit "compare_version_number" = [%test_eq: int](compare_version_number({major: 1, minor: 0, point: 0}, {major: 2, minor: 0, point: 0}), -1);
+let extract_version_number = cmd => {
-
+  switch (Util.run_process(cmd, ["--version"])) {
-let extract_version_number = (cmd) => {
+  | (Ok (), stdout) when String.length(stdout) > 0 =>
-  let full_cmd = cmd ++ " --version";
+    switch (Re.exec(semver_re, stdout)) {
-  switch (Core_unix.open_process_in(full_cmd) |> In_channel.input_line) {
+    | exception Stdlib.Not_found =>
-  | Some(stdout) => {
+      Error(
-      let substrings = Re.exec(semver_re, stdout);
+        Printf.sprintf(
+          "Stdout did not contain a version number for `%s --version`",
+          cmd,
+        ),
+      )
+    | substrings =>
       let groups = Re.Group.all(substrings);
       Ok({
         major: groups[1] |> int_of_string,
         minor: groups[2] |> int_of_string,
-        point: groups[3] |> int_of_string
+        point: groups[3] |> int_of_string,
-      })
+      });
-    }
-  | None => Error(Printf.sprintf("Failed executing '%s'\n", cmd))
     }
+  | _ => Error(Printf.sprintf("Failed executing '%s'", cmd))
+  };
 };
 
-let is_version_new_enough = (cur, needed) => {
+let is_new_enough = (cur, needed) => {
   switch (cur) {
-    | Ok(cur) => {
+  | Ok(cur) =>
-        switch (compare_version_number(cur, needed)) {
+    switch (compare(cur, needed)) {
     | x when x < 0 => Ok(false)
     | _ => Ok(true)
     }
-      }
   | Error(e) => Error(e)
-  }
+  };
-}
+};
 
-let preflight_versions = () => {
+let in_direnv = () =>
-  let in_direnv = switch (Sys.getenv("direnv")) {
+  switch (Sys.getenv("direnv")) {
   | Some(_) => true
   | None => false
   };
 
-  let is_nix_new_enough = is_version_new_enough(extract_version_number("nix"), required_nix_version);
+let preflight_versions = () => {
-  let is_direnv_new_enough = is_version_new_enough(extract_version_number("direnv"), required_direnv_version);
+  let is_nix_new_enough =
+    is_new_enough(extract_version_number("nix"), required_nix_version);
+  let is_direnv_new_enough =
+    is_new_enough(extract_version_number("direnv"), required_direnv_version);
 
-  switch (in_direnv, is_direnv_new_enough, is_nix_new_enough) {
+  switch (in_direnv(), is_direnv_new_enough, is_nix_new_enough) {
   | (false, _, _) => Error("Not in direnv!")
   | (_, Ok(false), _) => Error("Direnv version is not new enough")
   | (_, _, Ok(false)) => Error("Nix version is not new enough")
   | (_, Error(e), _) => Error(e)
   | (_, _, Error(e)) => Error(e)
   | (true, Ok(true), Ok(true)) => Ok()
-  }
+  };
 };

lib/flake_env__watches.re

@@ -9,40 +9,52 @@ module Util = Flake_env__util;
 type watch = {
   exists: bool,
   modtime: int,
-  path: string
+  path: string,
 };
 
 [@deriving yojson]
-type watches = array<watch>;
+type watches = array(watch);
 
 let get = () => {
-  let direnv_watch_str = Sys.getenv("DIRENV_WATCHES") |> Option.value_exn(~message="Environment missing DIRENV_WATCHES");
+  let direnv_watch_str =
-  let proc_info = Unix.create_process(~prog="direnv", ~args=["show_dump", direnv_watch_str]);
+    Sys.getenv("DIRENV_WATCHES")
+    |> Option.value_exn(~message="Environment missing DIRENV_WATCHES");
+  let proc_info =
+    Unix.create_process(
+      ~prog="direnv",
+      ~args=["show_dump", direnv_watch_str],
+    );
   let sub_stdout = Unix.in_channel_of_descr(proc_info.stdout);
 
   switch (Unix.waitpid(proc_info.pid)) {
-    | Ok() => Ok(watches_of_yojson(Yojson.Safe.from_channel(sub_stdout)))
+  | Ok () => Ok(watches_of_yojson(Yojson.Safe.from_channel(sub_stdout)))
   | _ => Error("Failed to parse watches")
-  }
+  };
 };
 
-let get_path = (doc) => String.drop_prefix(doc |> member("path") |> to_string, 11);
+let get_path = doc =>
+  String.drop_prefix(doc |> member("path") |> to_string, 11);
 
 let rec get_paths_from_doc = (doc, paths) => {
   let p = get_path(doc);
-  let sub_paths = List.concat(
+  let sub_paths =
-    doc |> member("inputs")
+    List.concat(
+      doc
+      |> member("inputs")
       |> to_assoc
-        |> List.map(~f=((_k, v)) => get_paths_from_doc(v, paths)));
+      |> List.map(~f=((_k, v)) => get_paths_from_doc(v, paths)),
-  List.concat([[p], sub_paths])
+    );
+  List.concat([[p], sub_paths]);
 };
 
 let get_input_paths = () => {
   switch (Util.nix(["flake", "archive", "--json", "--no-write-lock-file"])) {
-  | (Ok(), output) => get_paths_from_doc(Yojson.Safe.from_string(output), [])
+  | (Ok (), output) =>
-  | (Error(_), _) => {
+    get_paths_from_doc(Yojson.Safe.from_string(output), [])
-      Printf.eprintf("Failed to parse output of `nix flake archive --json`. Ignorning flake inputs. \n");
+  | (Error(_), _) =>
-      []
+    Printf.eprintf(
-    }
+      "Failed to parse output of `nix flake archive --json`. Ignorning flake inputs. \n",
-  }
+    );
+    [];
+  };
 };

lib/lib.re

@@ -1,3 +1,96 @@
+open Core;
+module Unix = Core_unix;
+
 module Util = Flake_env__util;
 module Watches = Flake_env__watches;
 module Versions = Flake_env__versions;
+
+let print_cur_cache = profile_rc => {
+  In_channel.read_all(profile_rc) |> Printf.printf("%s");
+};
+
+let clean_old_gcroots = layout_dir => {
+  Util.rmrf(layout_dir ++ "/flake-inputs/");
+  Util.rmrf(layout_dir);
+  Unix.mkdir_p(layout_dir ++ "/flake-inputs/");
+};
+
+let add_gcroot = (store_path, symlink) => {
+  switch (Util.nix(["build", "--out-link", symlink, store_path])) {
+  | (Ok (), _) => Ok()
+  | (err, _) => err
+  };
+};
+
+let freshen_cache = (layout_dir, hash, flake_specifier, other_args) => {
+  clean_old_gcroots(layout_dir);
+  let tmp_profile =
+    layout_dir
+    ++ "flake-tmp-profile."
+    ++ Core.Pid.to_string(Core_unix.getpid());
+
+  let pde_args = [
+    "print-dev-env",
+    "--profile",
+    tmp_profile,
+    flake_specifier,
+    ...other_args,
+  ];
+  let (exit_code, stdout_content) = Util.nix(pde_args);
+
+  let profile = layout_dir ++ "/flake-profile-" ++ hash;
+  let profile_rc = profile ++ ".rc";
+
+  switch (exit_code) {
+  | Ok () =>
+    Out_channel.with_file(
+      ~f=f => Out_channel.output_string(f, stdout_content),
+      profile_rc,
+    );
+    switch (add_gcroot(tmp_profile, profile)) {
+    | Ok () =>
+      Sys_unix.remove(tmp_profile);
+      let flake_input_cache_path = layout_dir ++ "/flake-inputs/";
+      let flake_inputs = Watches.get_input_paths();
+      flake_inputs
+      |> List.iter(~f=inpt => {
+           switch (
+             add_gcroot("/nix/store/" ++ inpt, flake_input_cache_path ++ inpt)
+           ) {
+           | Ok () => ()
+           | err =>
+             Printf.eprintf(
+               "Failed creating flake-input gcroot: %s\n",
+               Core_unix.Exit_or_signal.to_string_hum(err),
+             )
+           }
+         });
+      print_cur_cache(profile_rc);
+    | err =>
+      Printf.eprintf(
+        "Failed creating gcroot: %s\n",
+        Core_unix.Exit_or_signal.to_string_hum(err),
+      );
+      exit(1);
+    };
+  | err =>
+    Printf.eprintf(
+      "Failed evaluating flake: %s\n",
+      Core_unix.Exit_or_signal.to_string_hum(err),
+    );
+    exit(1);
+  };
+};
+
+let preflight = layout_directory => {
+  switch (
+    Versions.preflight_versions(),
+    Sys_unix.is_directory(layout_directory),
+  ) {
+  | (Ok(_), `Yes) => Ok()
+  | (Ok(_), _) =>
+    Unix.mkdir_p(layout_directory);
+    Ok();
+  | (err, _) => err
+  };
+};

tests/dune

@@ -0,0 +1,10 @@
+(tests
+ (names flake_env_test_versions flake_env_test_watches flake_env_test_util)
+ (deps spit_version.sh spit_gibberish.sh)
+ (libraries
+  lib
+  alcotest
+  core
+  core_unix
+  core_unix.sys_unix
+  core_unix.filename_unix))

tests/flake_env_test_util.re

@@ -0,0 +1,167 @@
+open Core;
+module Unix = Core_unix;
+
+open Lib.Util;
+
+let _pp_exit_or_signal = (pp_fmt, e) =>
+  Fmt.pf(pp_fmt, "%s", Unix.Exit_or_signal.to_string_hum(e));
+let _exit_or_signal_eq = (a, b) => Unix.Exit_or_signal.compare(a, b) == 0;
+let testable_exit_or_signal =
+  Alcotest.testable(_pp_exit_or_signal, _exit_or_signal_eq);
+
+let _syst_to_bool =
+  fun
+  | `Yes => true
+  | _ => false;
+
+let check_exit_or_signal =
+  Alcotest.(check(Alcotest.pair(testable_exit_or_signal, string)));
+let check_string = Alcotest.(check(string));
+let check_bool = Alcotest.(check(bool));
+let check_get_args =
+  Alcotest.(
+    check(
+      Alcotest.result(Alcotest.triple(string, string, list(string)), unit),
+    )
+  );
+
+let test_run_process_success = () =>
+  check_exit_or_signal(
+    "Returns expected",
+    (Ok(), ""),
+    run_process("true", []),
+  );
+
+let test_run_process_failure = () =>
+  check_exit_or_signal(
+    "Returns expected",
+    (Error(`Exit_non_zero(1)), ""),
+    run_process("false", []),
+  );
+
+let test_run_process_stdout = () =>
+  check_exit_or_signal(
+    "Returns expected",
+    (Ok(), "echoed\n"),
+    run_process("echo", ["echoed"]),
+  );
+
+let test_hash_one = () => {
+  check_string(
+    "Hash matches",
+    hash_files([|"../LICENSE"|]),
+    "b43cf2e824eb66ba0e8f939c08072a8e307b5e5f",
+  );
+};
+
+let test_hash_multiple = () => {
+  check_string(
+    "Hash matches",
+    hash_files([|"../LICENSE", "../LICENSE"|]),
+    "08304d8baeed02722f81252952b00f6ac011ce0c",
+  );
+};
+
+let test_hash_filters_nonexistent = () => {
+  check_string(
+    "Hash matches",
+    hash_files([|"../LICENSE", "FOOBARBAZ"|]),
+    "b43cf2e824eb66ba0e8f939c08072a8e307b5e5f",
+  );
+};
+
+let test_rmrf_file = () => {
+  let tmp_file_name = Filename_unix.temp_file("test", "txt");
+  rmrf(tmp_file_name);
+
+  check_bool(
+    "File removed",
+    false,
+    _syst_to_bool(Sys_unix.is_file(tmp_file_name)),
+  );
+};
+
+let test_rmrf_dir = () => {
+  let temp_dir_name = Filename_unix.temp_dir("test", "d");
+  let _ = Filename_unix.temp_file(~in_dir=temp_dir_name, "test", "txt");
+
+  rmrf(temp_dir_name);
+
+  check_bool(
+    "File removed",
+    false,
+    _syst_to_bool(Sys_unix.file_exists(temp_dir_name)),
+  );
+};
+
+let test_get_args_simple = () => {
+  check_get_args(
+    "Parses successfully",
+    Ok(("foo", "bar", ["oof", "rab", "zab"])),
+    get_args([|"000", "foo", "bar", "oof", "rab", "zab"|]),
+  );
+};
+
+let test_get_args_just_enough = () => {
+  check_get_args(
+    "Parses just enough args",
+    Ok(("foo", "bar", [])),
+    get_args([|"000", "foo", "bar"|]),
+  );
+};
+
+let test_get_args_error = () => {
+  check_get_args(
+    "Errors on too few args",
+    Error(),
+    get_args([|"000", "111"|]),
+  );
+};
+
+let () =
+  Alcotest.(
+    run(
+      "Watches",
+      [
+        (
+          "run_process",
+          [
+            test_case("Capture's Stdout", `Quick, test_run_process_stdout),
+            test_case("Success", `Quick, test_run_process_success),
+            test_case("Failure", `Quick, test_run_process_failure),
+          ],
+        ),
+        (
+          "hash_files",
+          [
+            test_case("Hashes one file", `Quick, test_hash_one),
+            test_case("Hashes multiple files", `Quick, test_hash_multiple),
+            test_case(
+              "Filters non-existent",
+              `Quick,
+              test_hash_filters_nonexistent,
+            ),
+          ],
+        ),
+        (
+          "rmrf helper",
+          [
+            test_case("Removes file", `Quick, test_rmrf_file),
+            test_case("Removes dir", `Quick, test_rmrf_dir),
+          ],
+        ),
+        (
+          "get_args",
+          [
+            test_case("Parses Args", `Quick, test_get_args_simple),
+            test_case(
+              "Parses just enough args",
+              `Quick,
+              test_get_args_just_enough,
+            ),
+            test_case("Handles too few args", `Quick, test_get_args_error),
+          ],
+        ),
+      ],
+    )
+  );

tests/flake_env_test_versions.re

@@ -0,0 +1,203 @@
+open Lib;
+
+let pprint = (pp_fmt, version) => {
+  Versions.(
+    Fmt.pf(
+      pp_fmt,
+      "{ major: %d, minor: %d, point: %d }",
+      version.major,
+      version.minor,
+      version.point,
+    )
+  );
+};
+let testable_version =
+  Alcotest.testable(pprint, (a, b) => Versions.compare(a, b) == 0);
+
+let check_version =
+  Alcotest.(check(Alcotest.result(testable_version, string)));
+
+let test_compare_equal = () => {
+  let a = Versions.init(1, 0, 0);
+  Alcotest.(check(int))("equal", 0, Versions.compare(a, a));
+};
+
+let test_compare_first_major_greater = () => {
+  let a = Versions.init(2, 0, 0);
+  let b = Versions.init(1, 0, 0);
+  Alcotest.(check(int))("First major greater", 1, Versions.compare(a, b));
+};
+
+let test_compare_first_minor_greater = () => {
+  let a = Versions.init(1, 1, 0);
+  let b = Versions.init(1, 0, 0);
+  Alcotest.(check(int))("First minor greater", 1, Versions.compare(a, b));
+};
+
+let test_compare_first_point_greater = () => {
+  let a = Versions.init(1, 0, 1);
+  let b = Versions.init(1, 0, 0);
+  Alcotest.(check(int))("First point greater", 1, Versions.compare(a, b));
+};
+
+let test_compare_second_major_greater = () => {
+  let a = Versions.init(1, 0, 0);
+  let b = Versions.init(2, 0, 0);
+  Alcotest.(check(int))("Second major greater", -1, Versions.compare(a, b));
+};
+
+let test_compare_second_minor_greater = () => {
+  let a = Versions.init(1, 0, 0);
+  let b = Versions.init(1, 1, 0);
+  Alcotest.(check(int))("Second minor greater", -1, Versions.compare(a, b));
+};
+
+let test_compare_second_point_greater = () => {
+  let a = Versions.init(1, 0, 0);
+  let b = Versions.init(1, 0, 1);
+  Alcotest.(check(int))("Second point greater", -1, Versions.compare(a, b));
+};
+
+let test_ine_cur_newer = () => {
+  let a = Ok(Versions.init(2, 0, 0));
+  let b = Versions.init(1, 0, 0);
+  let ine = Versions.is_new_enough(a, b);
+  Alcotest.(check(bool))("Curr newer", true, ine |> Result.get_ok);
+};
+
+let test_ine_cur_older = () => {
+  let a = Ok(Versions.init(1, 0, 0));
+  let b = Versions.init(2, 0, 0);
+  let ine = Versions.is_new_enough(a, b);
+  Alcotest.(check(bool))("Curr older", false, ine |> Result.get_ok);
+};
+
+let test_ine_cur_equal = () => {
+  let a = Versions.init(1, 0, 0);
+  let ine = Versions.is_new_enough(Ok(a), a);
+  Alcotest.(check(bool))("Curr equal", true, ine |> Result.get_ok);
+};
+
+let test_ine_error = () => {
+  let a = Error("foobarbaz");
+  let ine = Versions.is_new_enough(a, Versions.init(1, 0, 0));
+  Alcotest.(check(Alcotest.result(bool, string)))(
+    "Error bubbled",
+    Error("foobarbaz"),
+    ine,
+  );
+};
+
+let test_in_direnv_true = () => {
+  Core_unix.putenv(~key="direnv", ~data="direnv");
+  Alcotest.(check(bool))("In direnv", true, Versions.in_direnv());
+};
+
+let test_in_direnv_false = () => {
+  Core_unix.unsetenv("direnv");
+  Alcotest.(check(bool))("Not in direnv", false, Versions.in_direnv());
+};
+
+let test_extract_version_number_success = () => {
+  let result = Versions.extract_version_number("../tests/spit_version.sh");
+  check_version("Versions", Ok(Versions.init(1, 1, 1)), result);
+};
+
+let test_extract_version_number_no_version = () => {
+  let result = Versions.extract_version_number("../tests/spit_gibberish.sh");
+  check_version(
+    "Versions",
+    Error(
+      "Stdout did not contain a version number for `../tests/spit_gibberish.sh --version`",
+    ),
+    result,
+  );
+};
+
+let test_extract_version_number_nonexistent = () => {
+  let result = Versions.extract_version_number("nonexistent.sh");
+  check_version(
+    "Versions",
+    Error("Failed executing 'nonexistent.sh'"),
+    result,
+  );
+};
+
+// TODO: Test:
+// * preflight_versions? impure, but m
+let () =
+  Alcotest.(
+    run(
+      "Versions",
+      [
+        (
+          "compare",
+          [
+            test_case("Versions Equal", `Quick, test_compare_equal),
+            test_case(
+              "First Major Greater",
+              `Quick,
+              test_compare_first_major_greater,
+            ),
+            test_case(
+              "First Minor Greater",
+              `Quick,
+              test_compare_first_minor_greater,
+            ),
+            test_case(
+              "First Point Greater",
+              `Quick,
+              test_compare_first_point_greater,
+            ),
+            test_case(
+              "Second Major Greater",
+              `Quick,
+              test_compare_second_major_greater,
+            ),
+            test_case(
+              "Second Minor Greater",
+              `Quick,
+              test_compare_second_minor_greater,
+            ),
+            test_case(
+              "Second Point Greater",
+              `Quick,
+              test_compare_second_point_greater,
+            ),
+          ],
+        ),
+        (
+          "is_new_enough",
+          [
+            test_case("Curr Newer", `Quick, test_ine_cur_newer),
+            test_case("Curr Older", `Quick, test_ine_cur_older),
+            test_case("Curr Equal", `Quick, test_ine_cur_equal),
+            test_case("Error", `Quick, test_ine_error),
+          ],
+        ),
+        (
+          "in_direnv",
+          [
+            test_case("true", `Quick, test_in_direnv_true),
+            test_case("false", `Quick, test_in_direnv_false),
+          ],
+        ),
+        (
+          "extract_version_number",
+          [
+            test_case("success", `Quick, test_extract_version_number_success),
+            test_case(
+              "no version number",
+              `Quick,
+              test_extract_version_number_no_version,
+            ),
+            test_case(
+              "missing binary",
+              `Quick,
+              test_extract_version_number_nonexistent,
+            ),
+          ],
+        ),
+      ],
+    )
+  );

tests/flake_env_test_watches.re

@@ -0,0 +1,60 @@
+open Lib.Watches;
+
+let test_get_path_removes_prefix = () => {
+  let input = `Assoc([("path", `String("aaaaaaaaaaabbbbb"))]);
+  Alcotest.(check(string))("Prefix removed", "bbbbb", get_path(input));
+};
+
+let test_get_paths_from_doc = () => {
+  let input =
+    `Assoc([
+      ("path", `String("aaaaaaaaaaabbbbb")),
+      (
+        "inputs",
+        `Assoc([
+          (
+            "foo",
+            `Assoc([
+              ("path", `String("aaaaaaaaaaaccccc")),
+              (
+                "inputs",
+                `Assoc([
+                  (
+                    "bar",
+                    `Assoc([
+                      ("path", `String("aaaaaaaaaaaddddd")),
+                      ("inputs", `Assoc([])),
+                    ]),
+                  ),
+                ]),
+              ),
+            ]),
+          ),
+        ]),
+      ),
+    ]);
+  Alcotest.(check(list(string)))(
+    "Gathers all inputs",
+    ["bbbbb", "ccccc", "ddddd"],
+    get_paths_from_doc(input, []),
+  );
+};
+
+let () =
+  Alcotest.(
+    run(
+      "Watches",
+      [
+        (
+          "get_path",
+          [
+            test_case("Removes prefix", `Quick, test_get_path_removes_prefix),
+          ],
+        ),
+        (
+          "get_paths_from_doc",
+          [test_case("Collects all paths", `Quick, test_get_paths_from_doc)],
+        ),
+      ],
+    )
+  );

tests/spit_gibberish.sh

@@ -0,0 +1,3 @@
+#!/usr/bin/env sh
+
+echo "sdlfkjdsfweiojlsjslfj.dofiwoksdj/sfowiefjw0";

tests/spit_version.sh

@@ -0,0 +1,2 @@
+#!/usr/bin/env sh
+echo "1.1.1";