Construct a vga buffer for testing

src/vga_buffer.rs

@@ -140,3 +140,34 @@ pub fn _print(args: fmt::Arguments) {
     use core::fmt::Write;
     WRITER.lock().write_fmt(args).unwrap();
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    fn construct_writer() -> Writer {
+        use std::boxed::Box;
+
+        let buffer = construct_buffer();
+        Writer {
+            column_position: 0,
+            color_code: ColorCode::new(Color::Blue, Color::Magenta),
+            buffer: Box::leak(Box::new(buffer)),
+        }
+    }
+
+    fn construct_buffer() -> Buffer {
+        use array_init::array_init;
+
+        Buffer {
+            chars: array_init(|_| array_init(|_| Volatile::new(empty_char()))),
+        }
+    }
+
+    fn empty_char() -> ScreenChar {
+        ScreenChar {
+            ascii_character: b' ',
+            color_code: ColorCode::new(Color::Green, Color::Brown),
+        }
+    }
+}