diff --git a/rp2040/src/button_matrix.rs b/rp2040/src/button_matrix.rs
index ab22a23..155c732 100644
--- a/rp2040/src/button_matrix.rs
+++ b/rp2040/src/button_matrix.rs
@@ -112,7 +112,114 @@ impl<'a, const R: usize, const C: usize, const N: usize> ButtonMatrix<'a, R, C,
     ///
     /// For small `N` this copy is cheap. If needed, the API could be extended to
     /// return a reference in the future.
-    pub fn buttons_pressed(&mut self) -> [bool; N] {
+pub fn buttons_pressed(&mut self) -> [bool; N] {
         self.pressed
     }
 }
+
+#[cfg(all(test, feature = "std"))]
+mod tests {
+use super::*;
+use core::cell::Cell;
+use embedded_hal::digital::ErrorType;
+use std::rc::Rc;
+
+    struct MockInputPin {
+        state: Rc<Cell<bool>>,
+    }
+
+    impl MockInputPin {
+        fn new(state: Rc<Cell<bool>>) -> Self {
+            Self { state }
+        }
+    }
+
+    impl ErrorType for MockInputPin {
+        type Error = Infallible;
+    }
+
+    impl InputPin for MockInputPin {
+        fn is_high(&mut self) -> Result<bool, Self::Error> {
+            Ok(!self.state.get())
+        }
+
+        fn is_low(&mut self) -> Result<bool, Self::Error> {
+            Ok(self.state.get())
+        }
+    }
+
+    struct MockOutputPin {
+        state: Rc<Cell<bool>>,
+    }
+
+    impl MockOutputPin {
+        fn new(state: Rc<Cell<bool>>) -> Self {
+            Self { state }
+        }
+    }
+
+    impl ErrorType for MockOutputPin {
+        type Error = Infallible;
+    }
+
+    impl OutputPin for MockOutputPin {
+        fn set_high(&mut self) -> Result<(), Self::Error> {
+            self.state.set(true);
+            Ok(())
+        }
+
+        fn set_low(&mut self) -> Result<(), Self::Error> {
+            self.state.set(false);
+            Ok(())
+        }
+    }
+
+    fn matrix_fixture() -> (
+        ButtonMatrix<'static, 1, 1, 1>,
+        Rc<Cell<bool>>,
+        Rc<Cell<bool>>,
+    ) {
+        let row_state = Rc::new(Cell::new(false));
+        let col_state = Rc::new(Cell::new(false));
+
+        let row_pin: &'static mut dyn InputPin<Error = Infallible> =
+            Box::leak(Box::new(MockInputPin::new(row_state.clone())));
+        let col_pin: &'static mut dyn OutputPin<Error = Infallible> =
+            Box::leak(Box::new(MockOutputPin::new(col_state.clone())));
+
+        let rows: &'static mut [&'static mut dyn InputPin<Error = Infallible>; 1] =
+            Box::leak(Box::new([row_pin]));
+        let cols: &'static mut [&'static mut dyn OutputPin<Error = Infallible>; 1] =
+            Box::leak(Box::new([col_pin]));
+
+        let matrix = ButtonMatrix::new(rows, cols, 2);
+
+        (matrix, row_state, col_state)
+    }
+
+    #[test]
+    fn init_pins_sets_columns_high() {
+        let (mut matrix, _row_state, col_state) = matrix_fixture();
+        assert!(!col_state.get());
+        matrix.init_pins();
+        assert!(col_state.get());
+    }
+
+    #[test]
+    fn process_column_obeys_debounce() {
+        let (mut matrix, row_state, _col_state) = matrix_fixture();
+        let mut states = matrix.buttons_pressed();
+        assert!(!states[0]);
+        row_state.set(true);
+        matrix.process_column(0);
+        matrix.process_column(0);
+        states = matrix.buttons_pressed();
+        assert!(states[0]);
+
+        row_state.set(false);
+        matrix.process_column(0);
+        matrix.process_column(0);
+        states = matrix.buttons_pressed();
+        assert!(!states[0]);
+    }
+}
diff --git a/rp2040/src/mapping.rs b/rp2040/src/mapping.rs
index c8adb7c..2403708 100644
--- a/rp2040/src/mapping.rs
+++ b/rp2040/src/mapping.rs
@@ -163,3 +163,41 @@ pub fn configure_button_mappings(buttons: &mut [Button]) {
     buttons[BUTTON_FRONT_LEFT_EXTRA].usb_button = USB_BUTTON_30;
     buttons[BUTTON_FRONT_RIGHT_EXTRA].usb_button = USB_BUTTON_31;
 }
+
+#[cfg(all(test, feature = "std"))]
+mod tests {
+    use super::*;
+    use crate::buttons::{Button, TOTAL_BUTTONS};
+
+    #[test]
+    fn front_buttons_have_expected_mappings() {
+        let mut buttons = [Button::default(); TOTAL_BUTTONS];
+        configure_button_mappings(&mut buttons);
+
+        assert_eq!(buttons[BUTTON_FRONT_LEFT_LOWER].usb_button, USB_BUTTON_29);
+        assert_eq!(buttons[BUTTON_FRONT_RIGHT_UPPER].usb_button, USB_BUTTON_1);
+        assert_eq!(buttons[BUTTON_FRONT_CONFIG].usb_button_long, USB_BUTTON_3);
+    }
+
+    #[test]
+    fn long_press_flags_set_correctly() {
+        let mut buttons = [Button::default(); TOTAL_BUTTONS];
+        configure_button_mappings(&mut buttons);
+
+        assert!(buttons[BUTTON_TOP_LEFT_LOW].enable_long_press);
+        assert!(buttons[BUTTON_TOP_LEFT_LOW].enable_long_hold);
+        assert!(buttons[BUTTON_TOP_RIGHT_LOW].enable_long_press);
+        assert!(!buttons[BUTTON_TOP_RIGHT_LOW].enable_long_hold);
+    }
+
+    #[test]
+    fn hat_buttons_map_to_expected_ids() {
+        let mut buttons = [Button::default(); TOTAL_BUTTONS];
+        configure_button_mappings(&mut buttons);
+
+        assert_eq!(buttons[BUTTON_TOP_RIGHT_HAT_UP].usb_button, USB_HAT_UP);
+        assert_eq!(buttons[BUTTON_TOP_RIGHT_HAT_RIGHT].usb_button, USB_HAT_RIGHT);
+        assert_eq!(buttons[BUTTON_TOP_RIGHT_HAT_DOWN].usb_button, USB_HAT_DOWN);
+        assert_eq!(buttons[BUTTON_TOP_RIGHT_HAT_LEFT].usb_button, USB_HAT_LEFT);
+    }
+}