From 0ec07636a20a03a3833909013ee2e75eef401c3c Mon Sep 17 00:00:00 2001
From: mxhagen <markichnich@proton.me>
Date: Wed, 2 Apr 2025 14:00:21 +0200
Subject: [PATCH] add rudimentary tests for solvability of generated sudokus

---
 src/sudoku/generator.rs |  2 +-
 src/tests/generator.rs  | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/src/sudoku/generator.rs b/src/sudoku/generator.rs
index 2d100c2..b0483a5 100644
--- a/src/sudoku/generator.rs
+++ b/src/sudoku/generator.rs
@@ -91,7 +91,7 @@ pub fn generate_sudoku(difficulty: Difficulty) -> Board {
 /// TODO: currently empty cells needs to be recreated
 ///       on each recursive call, and are randomized anew
 ///       each time, which is an unnecessary overhead.
-fn solve_random(board: &mut Board) -> Result<(), ()> {
+pub fn solve_random(board: &mut Board) -> Result<(), ()> {
     let mut empty_cells: Vec<(usize, usize)> = Vec::new();
 
     let mut rows: Vec<usize> = (0..9).collect::<Vec<_>>();
diff --git a/src/tests/generator.rs b/src/tests/generator.rs
index 1891096..c313896 100644
--- a/src/tests/generator.rs
+++ b/src/tests/generator.rs
@@ -1,4 +1,4 @@
-use crate::{generate_sudoku, Board, Difficulty};
+use crate::{generator::*, Board};
 
 #[test]
 fn generated_sudoku_uniqueness() {
@@ -30,3 +30,33 @@ fn generated_sudoku_uniqueness() {
         iterations - uniques.len()
     );
 }
+
+
+#[test]
+fn generated_sudoku_solvability_small() {
+    use Difficulty::*;
+
+    let iterations = 20;
+
+    for difficulty in [Easy, Mid, Hard, Expert] {
+        for _ in 0..iterations {
+            let mut sudoku = generate_sudoku(difficulty);
+            solve_random(&mut sudoku).expect("Generated sudoku not solvable");
+        }
+    }
+}
+
+#[test]
+#[ignore]
+fn generated_sudoku_solvability_large() {
+    use Difficulty::*;
+
+    let iterations = 400;
+
+    for difficulty in [Easy, Mid, Hard, Expert] {
+        for _ in 0..iterations {
+            let mut sudoku = generate_sudoku(difficulty);
+            solve_random(&mut sudoku).expect("Generated sudoku not solvable");
+        }
+    }
+}