Added testcases for default size and color of the various displays

src/color.rs

@@ -1,5 +1,5 @@
 /// Only for the B/W Displays atm
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, PartialEq, Debug)]
 pub enum Color {
     Black,
     White,

src/epd1in54/mod.rs

@@ -284,3 +284,15 @@ where
         self.interface.command_with_data(Command::WRITE_LUT_REGISTER, buffer)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn epd_size() {
+        assert_eq!(WIDTH, 200);
+        assert_eq!(HEIGHT, 200);
+        assert_eq!(DEFAULT_BACKGROUND_COLOR, Color::White);
+    }
+}

src/epd2in9/mod.rs

@@ -286,3 +286,16 @@ where
         self.interface.command_with_data(Command::WRITE_LUT_REGISTER, buffer)
     }
 }
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn epd_size() {
+        assert_eq!(WIDTH, 128);
+        assert_eq!(HEIGHT, 296);
+        assert_eq!(DEFAULT_BACKGROUND_COLOR, Color::White);
+    }
+}

src/epd4in2/constants.rs

@@ -1,5 +1,8 @@
+use color::Color;
+
 pub(crate) const WIDTH: u16 = 400;
 pub(crate) const HEIGHT: u16 = 300;
+pub(crate) const DEFAULT_BACKGROUND_COLOR: Color = Color::White;
 
 pub(crate) const LUT_VCOM0: [u8; 44] = [
 0x00, 0x17, 0x00, 0x00, 0x00, 0x02,        

src/epd4in2/mod.rs

@@ -161,7 +161,7 @@ where
     /// ```
     fn new(spi: SPI, cs: CS, busy: BUSY, dc: DC, rst: RST, delay: Delay) -> Result<Self, ERR> {
         let interface = ConnectionInterface::new(spi, cs, busy, dc, rst, delay);
-        let color = Color::White;
+        let color = DEFAULT_BACKGROUND_COLOR;
 
         let mut epd = EPD4in2 {
             interface,
@@ -393,3 +393,16 @@ where
         Ok(())
     }
 }
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn epd_size() {
+        assert_eq!(WIDTH, 400);
+        assert_eq!(HEIGHT, 300);
+        assert_eq!(DEFAULT_BACKGROUND_COLOR, Color::White);
+    }
+}