diff --git a/src/event.rs b/src/event.rs
new file mode 100644
index 0000000..981fc88
--- /dev/null
+++ b/src/event.rs
@@ -0,0 +1,34 @@
+use crate::key::Key;
+
+/// Enum defining commands that can be issued by an `Element`.
+#[derive(Debug, Clone, PartialEq)]
+pub enum Command {
+    /// Renders the element with the specified state.
+    Render(usize),
+    /// Exits the application.
+    Exit,
+    /// Updates the element with the specified state.
+    Event(Event),
+    /// Pauses execution for the specified duration in milliseconds.
+    Sleep(u64),
+}
+
+/// Enum representing the possible responses from an element event.
+#[derive(Debug, Clone, PartialEq)]
+pub enum EventResponse {
+    /// Indicates that the event is complete.
+    Done,
+    /// Indicates no response.
+    None,
+    /// Issues a single command.
+    Command(Command),
+    /// Issues a list of commands.
+    CommandList(Vec<Command>),
+}
+
+/// Enum representing the possible responses from an element update.
+#[derive(Debug, Clone, PartialEq)]
+pub enum Event {
+    Key(Key),
+    State(usize),
+}
diff --git a/src/test/mod.rs b/src/test/mod.rs
new file mode 100644
index 0000000..1e0d296
--- /dev/null
+++ b/src/test/mod.rs
@@ -0,0 +1,13 @@
+use crate::{self as osui, rsx, ui::*, val, Element};
+
+pub fn app() -> Box<dyn Element> {
+    rsx! {
+        custom_component { width: val!(20), "" }
+    }
+}
+
+pub fn custom_component<'a>() -> Box<Div<'a>> {
+    rsx! {
+        button { style.clicked_background: Color::Red, "test" }
+    }
+}