diff --git a/dune-project b/dune-project
index c04ced4..b6c77b2 100644
--- a/dune-project
+++ b/dune-project
@@ -16,6 +16,7 @@
  (name get-activity-lib)
  (synopsis "Collect activity as markdown")
  (depends
+  (alcotest :with-test)
   astring
   curly
   fmt
diff --git a/get-activity-lib.opam b/get-activity-lib.opam
index a98a942..f350fbd 100644
--- a/get-activity-lib.opam
+++ b/get-activity-lib.opam
@@ -7,6 +7,7 @@ homepage: "https://github.com/tarides/get-activity"
 bug-reports: "https://github.com/tarides/get-activity/issues"
 depends: [
   "dune" {>= "2.8"}
+  "alcotest" {with-test}
   "astring"
   "curly"
   "fmt"
diff --git a/test/lib/alcotest_ext.ml b/test/lib/alcotest_ext.ml
new file mode 100644
index 0000000..330db4a
--- /dev/null
+++ b/test/lib/alcotest_ext.ml
@@ -0,0 +1,75 @@
+open Alcotest
+
+module Msg = struct
+  type 'a t = [ `Msg of 'a ]
+
+  let pp f fs (`Msg s : 'a t) = Format.fprintf fs "%a" f s
+  let eq f (`Msg s1 : 'a t) (`Msg s2 : 'a t) = f s1 s2
+
+  let testable t =
+    let pp = pp (Alcotest.pp t) in
+    let eq = eq (Alcotest.equal t) in
+    testable pp eq
+end
+
+let msg = Msg.testable
+let string_msg = msg string
+let or_msg x = result x string_msg
+
+module Yojson = struct
+  type t = Yojson.Safe.t
+
+  let pp = Yojson.Safe.pp
+  let eq = Yojson.Safe.equal
+  let testable : t testable = testable pp eq
+end
+
+let yojson = Yojson.testable
+
+module Curly = struct
+  module Meth = struct
+    type t = Curly.Meth.t
+
+    let pp = Curly.Meth.pp
+
+    let eq (x : t) (y : t) =
+      let x = Format.asprintf "%a" Curly.Meth.pp x in
+      let y = Format.asprintf "%a" Curly.Meth.pp y in
+      String.equal x y
+  end
+
+  module Header = struct
+    type t = Curly.Header.t
+
+    let pp = Curly.Header.pp
+
+    let eq (x : t) (y : t) =
+      let x = Format.asprintf "%a" Curly.Header.pp x in
+      let y = Format.asprintf "%a" Curly.Header.pp y in
+      String.equal x y
+  end
+end
+
+module Request = struct
+  type t = Get_activity.Graphql.request
+
+  let pp fs (x : t) =
+    Format.fprintf fs
+      "@[<hv 2>{@;\
+       meth = %a;@;\
+       url = %S@;\
+       headers =@ %a@;\
+       body =@ @[<hv 0>%a@];@]@;\
+       }"
+      Curly.Meth.pp x.meth x.url Curly.Header.pp x.headers Yojson.pp x.body
+
+  let eq (x : t) (y : t) =
+    Curly.Meth.eq x.meth y.meth
+    && String.equal x.url y.url
+    && Curly.Header.eq x.headers y.headers
+    && Yojson.eq x.body y.body
+
+  let testable = Alcotest.testable pp eq
+end
+
+let request = Request.testable
diff --git a/test/lib/alcotest_ext.mli b/test/lib/alcotest_ext.mli
new file mode 100644
index 0000000..d8aecc3
--- /dev/null
+++ b/test/lib/alcotest_ext.mli
@@ -0,0 +1,8 @@
+val msg : 'a Alcotest.testable -> [ `Msg of 'a ] Alcotest.testable
+val string_msg : [ `Msg of string ] Alcotest.testable
+
+val or_msg :
+  'a Alcotest.testable -> ('a, [ `Msg of string ]) result Alcotest.testable
+
+val yojson : Yojson.Safe.t Alcotest.testable
+val request : Get_activity.Graphql.request Alcotest.testable
diff --git a/test/lib/dune b/test/lib/dune
new file mode 100644
index 0000000..162d0b1
--- /dev/null
+++ b/test/lib/dune
@@ -0,0 +1,4 @@
+(test
+ (name main)
+ (package get-activity-lib)
+ (libraries get-activity-lib alcotest))
diff --git a/test/lib/main.ml b/test/lib/main.ml
new file mode 100644
index 0000000..1172be5
--- /dev/null
+++ b/test/lib/main.ml
@@ -0,0 +1,8 @@
+let () =
+  Alcotest.run "get-activity-lib"
+    [
+      Test_token.suite;
+      Test_period.suite;
+      Test_graphql.suite;
+      Test_contributions.suite;
+    ]
diff --git a/test/lib/test_contributions.ml b/test/lib/test_contributions.ml
new file mode 100644
index 0000000..fde6c91
--- /dev/null
+++ b/test/lib/test_contributions.ml
@@ -0,0 +1,456 @@
+open Get_activity
+
+module Testable = struct
+  module Datetime = struct
+    let pp fs x = Format.fprintf fs "%S" x
+    let eq = String.equal
+  end
+
+  module Item = struct
+    module Kind = struct
+      type t = [ `Issue | `PR | `Review of string | `New_repo ]
+
+      let pp fs = function
+        | `Issue -> Format.fprintf fs "`Issue"
+        | `PR -> Format.fprintf fs "`PR"
+        | `Review x -> Format.fprintf fs "`Review %S" x
+        | `New_repo -> Format.fprintf fs "`New_repo"
+
+      let eq (x : t) (y : t) =
+        match (x, y) with
+        | `Issue, `Issue | `PR, `PR | `New_repo, `New_repo -> true
+        | `Review x, `Review y -> String.equal x y
+        | _ -> false
+    end
+
+    type t = Contributions.item
+
+    let pp fs (x : t) =
+      Format.fprintf fs
+        "@[<hv 2>{@;\
+         repo = %S;@;\
+         kind = %a;@;\
+         date = %a;@;\
+         url = %S;@;\
+         title = %S;@;\
+         body = %S;@]@;\
+         }@,"
+        x.repo Kind.pp x.kind Datetime.pp x.date x.url x.title x.body
+
+    let eq (x : t) (y : t) =
+      String.equal x.repo y.repo && Kind.eq x.kind y.kind
+      && Datetime.eq x.date y.date && String.equal x.url y.url
+      && String.equal x.title y.title
+      && String.equal x.body y.body
+  end
+
+  module Repo_map = struct
+    type 'a t = 'a Contributions.Repo_map.t
+
+    let pp f fs (x : 'a t) =
+      Contributions.Repo_map.iter
+        (fun key v ->
+          Format.fprintf fs
+            "@[<hv 2>{@;key = %S;@;value =@ @[<hv 0>%a@];@]@;}@," key f v)
+        x
+
+    let eq = Contributions.Repo_map.equal
+  end
+
+  module Contributions = struct
+    type t = Contributions.t
+
+    let pp fs (x : t) =
+      Format.fprintf fs
+        "@[<hv 2>{@;username = %S;@;activity =@ @[<hv 0>%a@];@]@;}" x.username
+        (Repo_map.pp (Format.pp_print_list Item.pp))
+        x.activity
+
+    (* [List.equal] requires OCaml >= 4.12 *)
+    let list_equal eq lx ly =
+      try
+        List.iter2 (fun x y -> if not (eq x y) then failwith "not equal") lx ly;
+        true
+      with _ -> false
+
+    let eq (x : t) (y : t) =
+      String.equal x.username y.username
+      && Repo_map.eq (list_equal Item.eq) x.activity y.activity
+
+    let testable = Alcotest.testable pp eq
+  end
+
+  let contributions = Contributions.testable
+end
+
+let test_request =
+  let make_test name ~period ~token ~expected =
+    let name = Printf.sprintf "request: %s" name in
+    let test_fun () =
+      let actual = Contributions.request ~period ~token in
+      Alcotest.(check Alcotest_ext.request) name expected actual
+    in
+    (name, `Quick, test_fun)
+  in
+  [
+    make_test "no token" ~token:"" ~period:("", "")
+      ~expected:
+        {
+          meth = `POST;
+          url = "https://api.github.com/graphql";
+          headers = [ ("Authorization", "bearer ") ];
+          body =
+            `Assoc
+              [
+                ( "query",
+                  `String
+                    {|query($from: DateTime!, $to: DateTime!) {
+   viewer {
+    login
+    contributionsCollection(from: $from, to: $to) {
+      issueContributions(first: 100) {
+        nodes {
+          occurredAt
+          issue {
+            url
+            title
+            body
+            repository { nameWithOwner }
+          }
+        }
+      }
+      pullRequestContributions(first: 100) {
+        nodes {
+          occurredAt
+          pullRequest {
+            url
+            title
+            body
+            repository { nameWithOwner }
+          }
+        }
+      }
+      pullRequestReviewContributions(first: 100) {
+        nodes {
+          occurredAt
+          pullRequestReview {
+            url
+            pullRequest { title }
+            body
+            state
+            comments(first: 100) { nodes { body } }
+            repository { nameWithOwner }
+          }
+        }
+      }
+      repositoryContributions(first: 100) {
+        nodes {
+          occurredAt
+          repository {
+            url
+            nameWithOwner
+          }
+        }
+      }
+    }
+  }
+}|}
+                );
+                ( "variables",
+                  `Assoc [ ("from", `String ""); ("to", `String "") ] );
+              ];
+        };
+  ]
+
+let activity_example =
+  {|
+{
+  "data": {
+    "viewer": {
+      "login": "gpetiot",
+      "contributionsCollection": {
+        "issueContributions": {
+          "nodes": [
+            {
+              "occurredAt": "2024-03-04T11:55:37Z",
+              "issue": {
+                "url": "https://github.com/tarides/get-activity/issues/8",
+                "title": "Add the PR/issues comments to the result of okra generate",
+                "body": "xxx",
+                "repository": {
+                  "nameWithOwner": "tarides/get-activity"
+                }
+              }
+            },
+            {
+              "occurredAt": "2024-02-27T12:05:04Z",
+              "issue": {
+                "url": "https://github.com/tarides/okra/issues/165",
+                "title": "Make the `get-activity` package known to ocaml-ci",
+                "body": "xxx",
+                "repository": {
+                  "nameWithOwner": "tarides/okra"
+                }
+              }
+            }
+          ]
+        },
+        "pullRequestContributions": {
+          "nodes": [
+            {
+              "occurredAt": "2024-03-05T11:21:22Z",
+              "pullRequest": {
+                "url": "https://github.com/ocaml-ppx/ocamlformat/pull/2533",
+                "title": "Represent the expr sequence as a list",
+                "body": "xxx",
+                "repository": {
+                  "nameWithOwner": "ocaml-ppx/ocamlformat"
+                }
+              }
+            },
+            {
+              "occurredAt": "2024-03-04T17:20:11Z",
+              "pullRequest": {
+                "url": "https://github.com/realworldocaml/mdx/pull/450",
+                "title": "Add an 'exec' label to execute include OCaml blocks",
+                "body": "xxx",
+                "repository": {
+                  "nameWithOwner": "realworldocaml/mdx"
+                }
+              }
+            }
+          ]
+        },
+        "pullRequestReviewContributions": {
+          "nodes": [
+            {
+              "occurredAt": "2024-03-05T11:43:04Z",
+              "pullRequestReview": {
+                "url": "https://github.com/realworldocaml/mdx/pull/449#pullrequestreview-1916654244",
+                "pullRequest": {
+                  "title": "Add upgrade instructions in the changelog for #446"
+                },
+                "body": "xxx",
+                "state": "APPROVED",
+                "comments": {
+                  "nodes": []
+                },
+                "repository": {
+                  "nameWithOwner": "realworldocaml/mdx"
+                }
+              }
+            },
+            {
+              "occurredAt": "2024-02-28T11:09:41Z",
+              "pullRequestReview": {
+                "url": "https://github.com/tarides/okra/pull/166#pullrequestreview-1905972361",
+                "pullRequest": {
+                  "title": "Make README.md more precise"
+                },
+                "body": "xxx",
+                "state": "APPROVED",
+                "comments": {
+                  "nodes": []
+                },
+                "repository": {
+                  "nameWithOwner": "tarides/okra"
+                }
+              }
+            }
+          ]
+        },
+        "repositoryContributions": {
+          "nodes": [
+            {
+              "occurredAt": "2024-03-02T09:40:41Z",
+              "repository": {
+                "url": "https://github.com/gpetiot/config.ml",
+                "nameWithOwner": "gpetiot/config.ml"
+              }
+            },
+            {
+              "occurredAt": "2024-03-01T10:43:33Z",
+              "repository": {
+                "url": "https://github.com/gpetiot/js_of_ocaml",
+                "nameWithOwner": "gpetiot/js_of_ocaml"
+              }
+            }
+          ]
+        }
+      }
+    }
+  }
+}
+|}
+
+let activity_example_json = Yojson.Safe.from_string activity_example
+
+let contributions_example =
+  let open Contributions in
+  {
+    username = "gpetiot";
+    activity =
+      Repo_map.empty
+      |> Repo_map.add "gpetiot/config.ml"
+           [
+             {
+               repo = "gpetiot/config.ml";
+               kind = `New_repo;
+               date = "2024-03-02T09:40:41Z";
+               url = "https://github.com/gpetiot/config.ml";
+               title = "Created new repository";
+               body = "";
+             };
+           ]
+      |> Repo_map.add "gpetiot/js_of_ocaml"
+           [
+             {
+               repo = "gpetiot/js_of_ocaml";
+               kind = `New_repo;
+               date = "2024-03-01T10:43:33Z";
+               url = "https://github.com/gpetiot/js_of_ocaml";
+               title = "Created new repository";
+               body = "";
+             };
+           ]
+      |> Repo_map.add "ocaml-ppx/ocamlformat"
+           [
+             {
+               repo = "ocaml-ppx/ocamlformat";
+               kind = `PR;
+               date = "2024-03-05T11:21:22Z";
+               url = "https://github.com/ocaml-ppx/ocamlformat/pull/2533";
+               title = "Represent the expr sequence as a list";
+               body = "xxx";
+             };
+           ]
+      |> Repo_map.add "realworldocaml/mdx"
+           [
+             {
+               repo = "realworldocaml/mdx";
+               kind = `Review "APPROVED";
+               date = "2024-03-05T11:43:04Z";
+               url =
+                 "https://github.com/realworldocaml/mdx/pull/449#pullrequestreview-1916654244";
+               title = "Add upgrade instructions in the changelog for #446";
+               body = "xxx";
+             };
+             {
+               repo = "realworldocaml/mdx";
+               kind = `PR;
+               date = "2024-03-04T17:20:11Z";
+               url = "https://github.com/realworldocaml/mdx/pull/450";
+               title = "Add an 'exec' label to execute include OCaml blocks";
+               body = "xxx";
+             };
+           ]
+      |> Repo_map.add "tarides/get-activity"
+           [
+             {
+               repo = "tarides/get-activity";
+               kind = `Issue;
+               date = "2024-03-04T11:55:37Z";
+               url = "https://github.com/tarides/get-activity/issues/8";
+               title =
+                 "Add the PR/issues comments to the result of okra generate";
+               body = "xxx";
+             };
+           ]
+      |> Repo_map.add "tarides/okra"
+           [
+             {
+               repo = "tarides/okra";
+               kind = `Review "APPROVED";
+               date = "2024-02-28T11:09:41Z";
+               url =
+                 "https://github.com/tarides/okra/pull/166#pullrequestreview-1905972361";
+               title = "Make README.md more precise";
+               body = "xxx";
+             };
+             {
+               repo = "tarides/okra";
+               kind = `Issue;
+               date = "2024-02-27T12:05:04Z";
+               url = "https://github.com/tarides/okra/issues/165";
+               title = "Make the `get-activity` package known to ocaml-ci";
+               body = "xxx";
+             };
+           ];
+  }
+
+let test_of_json =
+  let make_test name ~from json ~expected =
+    let name = Printf.sprintf "of_json: %s" name in
+    let test_fun () =
+      let actual = Contributions.of_json ~from json in
+      Alcotest.(check Testable.contributions) name expected actual
+    in
+    (name, `Quick, test_fun)
+  in
+  [
+    make_test "no token" ~from:"" activity_example_json
+      ~expected:contributions_example;
+  ]
+
+let test_is_empty =
+  let make_test name ~input ~expected =
+    let name = Printf.sprintf "is_empty: %s" name in
+    let test_fun () =
+      let actual = Contributions.is_empty input in
+      Alcotest.(check bool) name expected actual
+    in
+    (name, `Quick, test_fun)
+  in
+  [
+    make_test "empty"
+      ~input:
+        { Contributions.username = ""; activity = Contributions.Repo_map.empty }
+      ~expected:true;
+    make_test "not empty" ~input:contributions_example ~expected:false;
+  ]
+
+let test_pp =
+  let make_test name ~input ~expected =
+    let name = Printf.sprintf "pp: %s" name in
+    let test_fun () =
+      let actual = Format.asprintf "%a" Contributions.pp input in
+      Alcotest.(check string) name expected actual
+    in
+    (name, `Quick, test_fun)
+  in
+  [
+    make_test "empty"
+      ~input:
+        { Contributions.username = ""; activity = Contributions.Repo_map.empty }
+      ~expected:"(no activity)";
+    make_test "not empty" ~input:contributions_example
+      ~expected:
+        "### gpetiot/config.ml\n\
+         Created repository \
+         [gpetiot/config.ml](https://github.com/gpetiot/config.ml).\n\
+         ### gpetiot/js_of_ocaml\n\
+         Created repository \
+         [gpetiot/js_of_ocaml](https://github.com/gpetiot/js_of_ocaml).\n\
+         ### ocaml-ppx/ocamlformat\n\
+         Represent the expr sequence as a list \
+         [#2533](https://github.com/ocaml-ppx/ocamlformat/pull/2533).  \n\
+         xxx### realworldocaml/mdx\n\
+         APPROVED Add upgrade instructions in the changelog for #446 \
+         [#449](https://github.com/realworldocaml/mdx/pull/449#pullrequestreview-1916654244).  \n\
+         xxx\n\
+         Add an 'exec' label to execute include OCaml blocks \
+         [#450](https://github.com/realworldocaml/mdx/pull/450).  \n\
+         xxx### tarides/get-activity\n\
+         Add the PR/issues comments to the result of okra generate \
+         [#8](https://github.com/tarides/get-activity/issues/8).  \n\
+         xxx### tarides/okra\n\
+         APPROVED Make README.md more precise \
+         [#166](https://github.com/tarides/okra/pull/166#pullrequestreview-1905972361).  \n\
+         xxx\n\
+         Make the `get-activity` package known to ocaml-ci \
+         [#165](https://github.com/tarides/okra/issues/165).  \n\
+         xxx";
+  ]
+
+let suite =
+  ("Contributions", test_request @ test_of_json @ test_is_empty @ test_pp)
diff --git a/test/lib/test_graphql.ml b/test/lib/test_graphql.ml
new file mode 100644
index 0000000..a58230d
--- /dev/null
+++ b/test/lib/test_graphql.ml
@@ -0,0 +1,24 @@
+open Get_activity
+
+let test_request =
+  let make_test name ?variables ~token ~query ~expected () =
+    let name = Printf.sprintf "request: %s" name in
+    let test_fun () =
+      let actual = Graphql.request ?variables ~token ~query () in
+      Alcotest.(check Alcotest_ext.request) name expected actual
+    in
+    (name, `Quick, test_fun)
+  in
+  [
+    make_test "no token" ~token:"" ~query:""
+      ~expected:
+        {
+          meth = `POST;
+          url = "https://api.github.com/graphql";
+          headers = [ ("Authorization", "bearer ") ];
+          body = `Assoc [ ("query", `String "") ];
+        }
+      ();
+  ]
+
+let suite = ("Graphql", test_request)
diff --git a/test/lib/test_period.ml b/test/lib/test_period.ml
new file mode 100644
index 0000000..989ef7b
--- /dev/null
+++ b/test/lib/test_period.ml
@@ -0,0 +1,33 @@
+open Get_activity
+
+let test_one_week =
+  let make_test name ~expected =
+    let name = Printf.sprintf "one_week: %s" name in
+    let test_fun () =
+      let actual = Period.one_week in
+      Alcotest.(check (float 0.)) name expected actual
+    in
+    (name, `Quick, test_fun)
+  in
+  [ make_test "default" ~expected:604800. ]
+
+let test_to_8601 =
+  let make_test name ~input ~expected =
+    let name = Printf.sprintf "to_8601: %s" name in
+    let test_fun () =
+      let actual = Period.to_8601 input in
+      Alcotest.(check string) name expected actual
+    in
+    (name, `Quick, test_fun)
+  in
+  [
+    make_test "zero" ~input:0. ~expected:"1970-01-01T00:00:00Z";
+    make_test "negative" ~input:(-1.) ~expected:"1969-12-31T23:59:59Z";
+    make_test "ten" ~input:10. ~expected:"1970-01-01T00:00:10Z";
+    make_test "one million" ~input:1_000_000. ~expected:"1970-01-12T13:46:40Z";
+    make_test "one billion" ~input:1_000_000_000.
+      ~expected:"2001-09-09T01:46:40Z";
+  ]
+
+let test_with_period = []
+let suite = ("Period", test_one_week @ test_to_8601 @ test_with_period)
diff --git a/test/lib/test_token.ml b/test/lib/test_token.ml
new file mode 100644
index 0000000..c339d75
--- /dev/null
+++ b/test/lib/test_token.ml
@@ -0,0 +1,25 @@
+open Get_activity
+
+let test_load =
+  let make_test name ~input ~expected =
+    let name = Printf.sprintf "load: %s" name in
+    let test_fun () =
+      let actual = Token.load input in
+      Alcotest.(check (Alcotest_ext.or_msg string)) name expected actual
+    in
+    (name, `Quick, test_fun)
+  in
+  let error_test name path =
+    let msg =
+      Format.sprintf
+        {|Can't open GitHub token file (%s: No such file or directory).
+Go to https://github.com/settings/tokens to generate one.|}
+        path
+    in
+    make_test name ~input:path ~expected:(Error (`Msg msg))
+  in
+  [
+    error_test "empty" ""; error_test "invalid path" "invalid-path/invalid-path";
+  ]
+
+let suite = ("Token", test_load)