diff --git a/.gitignore b/.gitignore
index ec464113b6..87b0876181 100644
--- a/.gitignore
+++ b/.gitignore
@@ -56,3 +56,6 @@ setup.log
 
 # Backup of opam lock file
 hazel.opam.locked.old
+
+# Code coverage
+_coverage/
diff --git a/Makefile b/Makefile
index 516016ddf8..5eef59a1d4 100644
--- a/Makefile
+++ b/Makefile
@@ -66,5 +66,13 @@ test:
 watch-test:
 	dune build @ocaml-index @fmt @runtest --auto-promote --watch
 
+coverage:
+	dune build @src/fmt @test/fmt --auto-promote src test --profile dev
+	dune runtest --instrument-with bisect_ppx --force
+	bisect-ppx-report summary
+
+generate-coverage-html:
+	bisect-ppx-report html
+
 clean:
 	dune clean
diff --git a/README.md b/README.md
index a15bdd424e..15caf27308 100644
--- a/README.md
+++ b/README.md
@@ -197,6 +197,9 @@ You can run all of the unit tests located in `test` by running `make test`.
 
 Unit tests are written using the [Alcotest framework](https://github.com/mirage/alcotest).
 
+#### Coverage
+Code coverage is provided by [bisect_ppx](https://github.com/aantron/bisect_ppx). To collect coverage statistics from tests run `make coverage`. After coverage statistics are generated, running `make generate-coverage-html` will generate a local webpage at `_coverage/index.html` that can be viewed to see line coverage per module.
+
 ### Continuous Integration
 
 When you push your branch to the main `hazelgrove/hazel` repository, we 
diff --git a/dune-project b/dune-project
index 1194593485..4dd3442bc4 100644
--- a/dune-project
+++ b/dune-project
@@ -26,9 +26,11 @@
   (menhir
    (>= 2.0))
   yojson
-  reason
+  (reason (>= 3.12.0))
   ppx_yojson_conv_lib
   ppx_yojson_conv
+  incr_dom
+  bisect_ppx
   (omd (>= 2.0.0~alpha4))
   ezjs_idb
   bonsai
diff --git a/hazel.opam b/hazel.opam
index e78b188325..09ee887ab3 100644
--- a/hazel.opam
+++ b/hazel.opam
@@ -11,9 +11,10 @@ depends: [
   "ocaml" {>= "5.2.0"}
   "menhir" {>= "2.0"}
   "yojson"
-  "reason"
+  "reason" {>= "3.12.0"}
   "ppx_yojson_conv_lib"
   "ppx_yojson_conv"
+  "bisect_ppx"
   "omd" {>= "2.0.0~alpha4"}
   "ezjs_idb"
   "bonsai"
diff --git a/hazel.opam.locked b/hazel.opam.locked
index b2cfce2cea..856b83ad33 100644
--- a/hazel.opam.locked
+++ b/hazel.opam.locked
@@ -39,6 +39,7 @@ depends: [
   "bigstringaf" {= "0.10.0"}
   "bin_prot" {= "v0.16.0"}
   "bonsai" {= "v0.16.0"}
+  "bisect_ppx" {= "2.8.3"}
   "camlp-streams" {= "5.0.1"}
   "chrome-trace" {= "3.16.0"}
   "cmdliner" {= "1.3.0"}
diff --git a/src/haz3lcore/dune b/src/haz3lcore/dune
index 77e2ca3fe1..a0d9770816 100644
--- a/src/haz3lcore/dune
+++ b/src/haz3lcore/dune
@@ -4,6 +4,8 @@
  (name haz3lcore)
  (libraries util sexplib unionFind uuidm virtual_dom yojson core)
  (js_of_ocaml)
+ (instrumentation
+  (backend bisect_ppx))
  (preprocess
   (pps
    ppx_yojson_conv
diff --git a/src/haz3lweb/Main.re b/src/haz3lweb/Main.re
index af8058b770..16811a32cb 100644
--- a/src/haz3lweb/Main.re
+++ b/src/haz3lweb/Main.re
@@ -4,8 +4,6 @@ open Haz3lweb;
 open Bonsai.Let_syntax;
 
 let scroll_to_caret = ref(true);
-let edit_action_applied = ref(true);
-let last_edit_action = ref(JsUtil.timestamp());
 
 let restart_caret_animation = () =>
   // necessary to trigger reflow
@@ -19,16 +17,24 @@ let restart_caret_animation = () =>
   | _ => ()
   };
 
-let apply = (model, action, ~schedule_action): Model.t => {
+let apply = (model, action, ~schedule_action, ~schedule_autosave): Model.t => {
   restart_caret_animation();
   if (UpdateAction.is_edit(action)) {
-    last_edit_action := JsUtil.timestamp();
-    edit_action_applied := true;
+    schedule_autosave(
+      BonsaiUtil.Alarm.Action.SetAlarm(
+        Core.Time_ns.add(Core.Time_ns.now(), Core.Time_ns.Span.of_sec(1.0)),
+      ),
+    );
+  } else {
+    schedule_autosave(
+      BonsaiUtil.Alarm.Action.SnoozeAlarm(
+        Core.Time_ns.add(Core.Time_ns.now(), Core.Time_ns.Span.of_sec(1.0)),
+      ),
+    );
   };
   if (Update.should_scroll_to_caret(action)) {
     scroll_to_caret := true;
   };
-  last_edit_action := JsUtil.timestamp();
   switch (
     try({
       let new_model = Update.apply(model, action, ~schedule_action);
@@ -53,16 +59,6 @@ let apply = (model, action, ~schedule_action): Model.t => {
   };
 };
 
-let app =
-  Bonsai.state_machine0(
-    (module Model),
-    (module Update),
-    ~apply_action=
-      (~inject, ~schedule_event) =>
-        apply(~schedule_action=x => schedule_event(inject(x))),
-    ~default_model=Model.load(Model.blank),
-  );
-
 /* This subcomponent is used to run an effect once when the app starts up,
    After the first draw */
 let on_startup = effect => {
@@ -80,31 +76,44 @@ let on_startup = effect => {
 };
 
 let view = {
-  let%sub app = app;
+  let%sub save_scheduler = BonsaiUtil.Alarm.alarm;
+  let%sub app =
+    Bonsai.state_machine1(
+      (module Model),
+      (module Update),
+      ~apply_action=
+        (~inject, ~schedule_event, input) => {
+          let schedule_action = x => schedule_event(inject(x));
+          let schedule_autosave = action =>
+            switch (input) {
+            | Active((_, alarm_inject)) =>
+              schedule_event(alarm_inject(action))
+            | Inactive => ()
+            };
+          apply(~schedule_action, ~schedule_autosave);
+        },
+      ~default_model=Model.load(Model.blank),
+      save_scheduler,
+    );
   let%sub () = {
     on_startup(
       Bonsai.Value.map(~f=((_model, inject)) => inject(Startup), app),
     );
   };
-  let%sub after_display = {
-    let%arr (_model, inject) = app;
-    if (scroll_to_caret.contents) {
-      scroll_to_caret := false;
-      JsUtil.scroll_cursor_into_view_if_needed();
-    };
-    if (edit_action_applied^
-        && JsUtil.timestamp()
-        -. last_edit_action^ > 1000.0) {
-      /* If an edit action has been applied, but no other edit action
-         has been applied for 1 second, save the model. */
-      edit_action_applied := false;
-      print_endline("Saving...");
-      inject(Update.Save);
-    } else {
-      Ui_effect.Ignore;
-    };
+  let after_display = {
+    Bonsai.Effect.of_sync_fun(
+      () =>
+        if (scroll_to_caret.contents) {
+          scroll_to_caret := false;
+          JsUtil.scroll_cursor_into_view_if_needed();
+        },
+      (),
+    );
   };
-  let%sub () = Bonsai.Edge.after_display(after_display);
+  let save_effect = Bonsai.Value.map(~f=((_, g)) => g(Update.Save), app);
+  let%sub () = BonsaiUtil.Alarm.listen(save_scheduler, ~event=save_effect);
+  let%sub () =
+    Bonsai.Edge.after_display(after_display |> Bonsai.Value.return);
   let%arr (model, inject) = app;
   Haz3lweb.Page.view(~inject, model);
 };
diff --git a/src/haz3lweb/Update.re b/src/haz3lweb/Update.re
index 1a47210a0e..43a5e593f6 100644
--- a/src/haz3lweb/Update.re
+++ b/src/haz3lweb/Update.re
@@ -508,7 +508,9 @@ let apply = (model: Model.t, update: t, ~schedule_action): Result.t(Model.t) =>
     | DebugConsole(key) =>
       DebugConsole.print(model, key);
       Ok(model);
-    | Save => Model.save_and_return(model)
+    | Save =>
+      print_endline("Saving...");
+      Model.save_and_return(model);
     | InitImportAll(file) =>
       JsUtil.read_file(file, data => schedule_action(FinishImportAll(data)));
       Ok(model);
diff --git a/src/haz3lweb/dune b/src/haz3lweb/dune
index d3e42ec636..e2792b76b8 100644
--- a/src/haz3lweb/dune
+++ b/src/haz3lweb/dune
@@ -8,6 +8,8 @@
 (library
  (name workerServer)
  (modules WorkerServer)
+ (instrumentation
+  (backend bisect_ppx))
  (libraries
   bonsai
   bonsai.web
@@ -29,6 +31,8 @@
 
 (library
  (name haz3lweb)
+ (instrumentation
+  (backend bisect_ppx))
  (modules
   (:standard \ Main)
   \
@@ -55,7 +59,8 @@
    ppx_let
    ppx_sexp_conv
    ppx_deriving.show
-   ppx_yojson_conv)))
+   ppx_yojson_conv
+   bonsai.ppx_bonsai)))
 
 (executable
  (name main)
diff --git a/src/pretty/dune b/src/pretty/dune
index 868d03defc..c131965aff 100644
--- a/src/pretty/dune
+++ b/src/pretty/dune
@@ -3,6 +3,8 @@
 (library
  (name pretty)
  (libraries util sexplib)
+ (instrumentation
+  (backend bisect_ppx))
  (preprocess
   (pps ppx_let ppx_sexp_conv)))
 
diff --git a/src/util/BonsaiUtil.re b/src/util/BonsaiUtil.re
new file mode 100644
index 0000000000..127172ce21
--- /dev/null
+++ b/src/util/BonsaiUtil.re
@@ -0,0 +1,42 @@
+open Core;
+open Bonsai;
+open Bonsai.Let_syntax;
+
+module Alarm = {
+  module Action = {
+    [@deriving sexp]
+    type t =
+      | SetAlarm(Time_ns.Alternate_sexp.t)
+      | SnoozeAlarm(Time_ns.Alternate_sexp.t)
+      | UnsetAlarm;
+  };
+
+  let alarm =
+    state_machine0(
+      (module Time_ns.Alternate_sexp),
+      (module Action),
+      ~default_model=Time_ns.max_value_representable,
+      ~apply_action=(~inject as _, ~schedule_event as _, model, action) => {
+      switch (action) {
+      | SetAlarm(time) => time
+      | SnoozeAlarm(time) => Time_ns.max(time, model)
+      | UnsetAlarm => Time_ns.max_value_representable
+      }
+    });
+
+  let listen = (alarm, ~event) => {
+    let%sub before_or_after = Clock.at(alarm |> Value.map(~f=fst));
+    Edge.on_change(
+      (module Clock.Before_or_after),
+      before_or_after,
+      ~callback={
+        open Clock.Before_or_after;
+        let%map (_, inject) = alarm
+        and event = event;
+        fun
+        | After => Effect.Many([inject(Action.UnsetAlarm), event])
+        | Before => Effect.Ignore;
+      },
+    );
+  };
+};
diff --git a/src/util/Util.re b/src/util/Util.re
index c901907b60..2c7f084100 100644
--- a/src/util/Util.re
+++ b/src/util/Util.re
@@ -1,4 +1,5 @@
 module Aba = Aba;
+module BonsaiUtil = BonsaiUtil;
 module Direction = Direction;
 module Either = Either;
 module IntMap = IntMap;
diff --git a/src/util/dune b/src/util/dune
index a3494db579..f50e6ac0f7 100644
--- a/src/util/dune
+++ b/src/util/dune
@@ -2,13 +2,16 @@
  (name util)
  (libraries re base ptmap bonsai bonsai.web virtual_dom yojson)
  (js_of_ocaml)
+ (instrumentation
+  (backend bisect_ppx))
  (preprocess
   (pps
    ppx_yojson_conv
    js_of_ocaml-ppx
    ppx_let
    ppx_sexp_conv
-   ppx_deriving.show)))
+   ppx_deriving.show
+   bonsai.ppx_bonsai)))
 
 (env
  (dev
diff --git a/test/dune b/test/dune
index 832c9689f2..3b9dc8bb2e 100644
--- a/test/dune
+++ b/test/dune
@@ -2,7 +2,7 @@
 
 (test
  (name haz3ltest)
- (libraries haz3lcore alcotest junit junit_alcotest)
+ (libraries haz3lcore alcotest junit junit_alcotest bisect_ppx.runtime)
  (modes js)
  (preprocess
-  (pps js_of_ocaml-ppx)))
+  (pps js_of_ocaml-ppx ppx_deriving.show)))
diff --git a/test/haz3ltest.re b/test/haz3ltest.re
index 03cebe774c..8e4a838b0a 100644
--- a/test/haz3ltest.re
+++ b/test/haz3ltest.re
@@ -13,3 +13,4 @@ let (suite, _) =
     ],
   );
 Junit.to_file(Junit.make([suite]), "junit_tests.xml");
+Bisect.Runtime.write_coverage_data();