Impl: Display trait for Playfield

Ref: Move new to tests and refactor tests in nested mod

src/main.rs

@@ -24,32 +24,31 @@ struct Field {
     value: Option<u32>,
 }
 
+use std::fmt;
 impl Playfield {
     fn new(size: usize) -> Playfield {
-        let fields = vec![
-            vec![
-                Field {
-                    possible_values: Vec::<u32>::new(),
-                    value: None
-                };
-                size
-            ];
-            size
-        ];
         Self {
-            fields,
+            fields: vec![vec![Field::default(); size]; size],
             open_fields: Vec::<u32>::new(),
         }
     }
 }
 
+impl fmt::Display for Playfield {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut result = String::new();
+        for row in &self.fields {
+            for field in row {
+                result += &field.value.unwrap_or_else(|| 0).to_string();
+                result += " ";
+            }
+            result += "\n";
+        }
+        write!(f, "{}", result)
+    }
+}
+
 impl Field {
-    fn new(value: u32) -> Field {
-        Self {
-            possible_values: Vec::<u32>::new(),
-            value: Some(value),
-        }
-    }
     fn default() -> Field {
         Self {
             possible_values: Vec::<u32>::new(),
@@ -62,6 +61,8 @@ fn main() {
     let cli = Cli::parse();
 
     let playfield = parse_playfield(&cli.field, cli.field_size);
+
+    println!("Input:\n{}", playfield)
 }
 
 fn parse_playfield(field: &String, field_size: usize) -> Playfield {
@@ -105,8 +106,20 @@ fn is_right_field_size(field: &Vec<&str>, field_size: usize) -> bool {
 mod tests {
     use super::*;
 
+    impl Field {
+        fn new(value: u32) -> Field {
+            Self {
+                possible_values: Vec::<u32>::new(),
+                value: Some(value),
+            }
+        }
+    }
+
+    mod parse_field {
+        use super::super::*;
+
         #[test]
-    fn test_parse_field() {
+        fn simple() {
             let input = "1 2 3 0 0 0 3 2 1";
             let field_size = 3;
 
@@ -127,7 +140,7 @@ mod tests {
 
         #[test]
         #[should_panic(expected = "Input must have dimension of size 2x2")]
-    fn test_parse_field_too_long_input() {
+        fn too_long_input() {
             let input = "1 2 3 0 0 0 3 2 1";
             let field_size = 2;
 
@@ -136,7 +149,7 @@ mod tests {
 
         #[test]
         #[should_panic(expected = "Input must have dimension of size 3x3")]
-    fn test_parse_field_too_short_input() {
+        fn too_short_input() {
             let input = "1 2 3";
             let field_size = 3;
 
@@ -145,10 +158,11 @@ mod tests {
 
         #[test]
         #[should_panic(expected = "Input must contain only digits followed by space")]
-    fn test_parse_field_wrong_character() {
+        fn wrong_character() {
             let input = "1 2 3 0 0 0 3 2 a";
             let field_size = 3;
 
             let _ = parse_playfield(&input.to_string(), field_size);
         }
     }
+}