day8 tests

day8/src/main.rs

@@ -1,10 +1,25 @@
+fn merge_layers(layers: &[&[u8]]) -> Vec<u8> {
+	let mut image = Vec::new();
+	image.resize(layers[0].len(), 2);
+	for layer in layers {
+		for (ndx, b) in layer.into_iter().enumerate() {
+			let digit = *b - b'0';
+			if image[ndx] != 2 { continue; }
+			image[ndx] = digit;
+		}
+	}
+	image
+}
+
+fn split_layers(input: &[u8], image_size: usize) -> Vec<&[u8]> {
+	assert_eq!(input.len() % image_size, 0);
+	input.chunks(image_size).collect::<Vec<_>>()
+}
+
 fn main() {
-	let input = include_str!("input.txt").as_bytes();
+	let input = include_bytes!("input.txt");
+	let layers = split_layers(input, 6*25);
 
-	const LAYER_SIZE: usize = 6*25;
-	assert_eq!(input.len() % LAYER_SIZE, 0);
-
-	let layers = input.chunks(LAYER_SIZE).collect::<Vec<_>>();
 	let min0_product12 = layers.iter().map(|layer| {
 		let mut count = [0, 0, 0];
 		for b in *layer {
@@ -17,14 +32,7 @@ fn main() {
 	}).min_by_key(|(zeroes, _product12)| *zeroes).unwrap().1;
 	println!("Product of counts of 1 and 2 for the layer with min 0s: {}", min0_product12);
 
-	let mut image = [2u8; LAYER_SIZE];
-	for layer in layers {
-		for (ndx, b) in layer.into_iter().enumerate() {
-			let digit = *b - b'0';
-			if image[ndx] != 2 { continue; }
-			image[ndx] = digit;
-		}
-	}
+	let image = merge_layers(&layers);
 
 	for row in image.chunks(25) {
 		for cell in row {
@@ -36,3 +44,19 @@ fn main() {
 		println!("");
 	}
 }
+
+#[cfg(test)]
+mod day8test {
+	use super::*;
+
+	#[test]
+	fn examples1() {
+		// no runnable examples
+	}
+	
+	#[test]
+	fn examples2() {
+		let layers = split_layers(b"0222112222120000", 4);
+		assert_eq!(merge_layers(&layers), [0, 1, 1, 0]);
+	}
+}