3 files changed, 158 insertions, 0 deletions
diff --git a/test/apps/counter.gleam b/test/apps/counter.gleam
new file mode 100644
index 0000000..b58b2ee
--- /dev/null
+++ b/test/apps/counter.gleam
@@ -0,0 +1,41 @@
+// IMPORTS ---------------------------------------------------------------------
+
+import gleam/int
+import lustre/element.{text}
+import lustre/element/html.{button, div, p}
+import lustre/event
+
+// MODEL -----------------------------------------------------------------------
+
+pub type Model =
+  Int
+
+pub fn init(count) {
+  count
+}
+
+// UPDATE ----------------------------------------------------------------------
+
+pub type Msg {
+  Increment
+  Decrement
+}
+
+pub fn update(model, msg) {
+  case msg {
+    Increment -> model + 1
+    Decrement -> model - 1
+  }
+}
+
+// VIEW ------------------------------------------------------------------------
+
+pub fn view(model) {
+  let count = int.to_string(model)
+
+  div([], [
+    p([], [text(count)]),
+    button([event.on_click(Decrement)], [text("-")]),
+    button([event.on_click(Increment)], [text("+")]),
+  ])
+}
diff --git a/test/apps/static.gleam b/test/apps/static.gleam
new file mode 100644
index 0000000..d41964a
--- /dev/null
+++ b/test/apps/static.gleam
@@ -0,0 +1,17 @@
+// IMPORTS ---------------------------------------------------------------------
+
+import lustre/attribute.{src}
+import lustre/element.{text}
+import lustre/element/html.{body, h1, head, html, img, title}
+
+// VIEW ------------------------------------------------------------------------
+
+pub fn view() {
+  html([], [
+    head([], [title([], "Hello, World!")]),
+    body([], [
+      h1([], [text("Hello, World!")]),
+      img([src("https://source.unsplash.com/random")]),
+    ]),
+  ])
+}
diff --git a/test/lustre_test.gleam b/test/lustre_test.gleam
new file mode 100644
index 0000000..c90dc8b
--- /dev/null
+++ b/test/lustre_test.gleam
@@ -0,0 +1,100 @@
+// IMPORTS ---------------------------------------------------------------------
+
+import apps/counter
+import apps/static
+import birdie
+import gleam/erlang/process
+import gleam/function
+import gleam/json
+import gleeunit
+import lustre
+import lustre/element
+import lustre/internals/patch
+import lustre/runtime.{Debug, Dispatch, Shutdown, View}
+
+// MAIN ------------------------------------------------------------------------
+
+pub fn main() {
+  gleeunit.main()
+}
+
+// TESTS -----------------------------------------------------------------------
+
+pub fn static_test() {
+  let title = "Can render static HTML"
+  let el = static.view()
+
+  birdie.snap(element.to_string(el), title)
+}
+
+pub fn counter_init_test() {
+  let title = "Can render an application's initial state."
+  let app = lustre.simple(counter.init, counter.update, counter.view)
+  let assert Ok(runtime) = lustre.start_actor(app, 0)
+  let el =
+    process.call(
+      runtime,
+      function.curry2(process.send)
+      |> function.compose(View)
+      |> function.compose(Debug),
+      100,
+    )
+
+  birdie.snap(element.to_string(el), title)
+  process.send(runtime, Shutdown)
+}
+
+pub fn counter_update_test() {
+  let title = "Can render an application's state after some updates."
+  let app = lustre.simple(counter.init, counter.update, counter.view)
+  let assert Ok(runtime) = lustre.start_actor(app, 0)
+
+  process.send(runtime, Dispatch(counter.Increment))
+  process.send(runtime, Dispatch(counter.Increment))
+  process.send(runtime, Dispatch(counter.Increment))
+
+  let el =
+    process.call(
+      runtime,
+      function.curry2(process.send)
+      |> function.compose(View)
+      |> function.compose(Debug),
+      100,
+    )
+
+  birdie.snap(element.to_string(el), title)
+  process.send(runtime, Shutdown)
+}
+
+pub fn counter_diff_test() {
+  let title = "Can compute a diff from one render to the next"
+  let app = lustre.simple(counter.init, counter.update, counter.view)
+  let assert Ok(runtime) = lustre.start_actor(app, 0)
+
+  let prev =
+    process.call(
+      runtime,
+      function.curry2(process.send)
+      |> function.compose(View)
+      |> function.compose(Debug),
+      100,
+    )
+
+  process.send(runtime, Dispatch(counter.Increment))
+  process.send(runtime, Dispatch(counter.Increment))
+  process.send(runtime, Dispatch(counter.Increment))
+
+  let next =
+    process.call(
+      runtime,
+      function.curry2(process.send)
+      |> function.compose(View)
+      |> function.compose(Debug),
+      100,
+    )
+
+  let diff = patch.elements(prev, next)
+
+  birdie.snap(json.to_string(patch.element_diff_to_json(diff)), title)
+  process.send(runtime, Shutdown)
+}