working on FEC tests again

• pass n to try_all_decoding_combinations and don't try to decode when shards have been recoded (\#shards > n) and there are no recoded shards in the k combination under review (\max(is) < n)
• pass recoding_steps and should_not_be_decodable as arguments to end_to_end_with_recoding_template
• fix n = 5 => this leads to tests that run in less than 10sec again
• add (k, n) = (8, 10) => tests still run in less than 13sec
• split recoding scenarii into "simple" and "chain"
• show indices in a "pretty" format, i.e. showing indices greater than n as (n), (n + 1), ...

src/fec.rs

@@ -306,9 +306,16 @@ mod tests {
         n: usize,
         recoding_steps: Vec<Vec<usize>>,
         should_not_be_decodable: Vec<Vec<usize>>,
+        name: &str,
     ) {
         let mut rng = ark_std::test_rng();
-        let test_case = format!("TEST | data: {} bytes, k: {}, n: {}", data.len(), k, n);
+        let test_case = format!(
+            "TEST | data: {} bytes, k: {}, n: {}, scenario: {}",
+            data.len(),
+            k,
+            n,
+            name
+        );
 
         let mut shards = encode::<F>(data, &Matrix::random(k, n, &mut rng))
             .unwrap_or_else(|_| panic!("could not encode {test_case}"));
@@ -353,33 +360,44 @@ mod tests {
         let ks = [3, 5];
         let n = 5;
 
-        let recoding_steps = vec![
-            vec![2, 4],       // =  n
-            vec![1, 3],       // = (n + 1)
-            vec![n, (n + 1)], // = (n + 2) = ((2, 4), (1, 3))
-            vec![0],          // = (n + 3) = (0)
-            vec![(n + 3)],    // = (n + 4) = (0)
-        ];
-        let should_not_be_decodable = vec![
-            vec![2, 4, n],
-            vec![1, 3, (n + 1)],
-            vec![n, (n + 1), (n + 2)],
-            vec![1, 3, n, (n + 2)],
-            vec![2, 4, (n + 1), (n + 2)],
-            vec![1, 2, 3, 4, (n + 2)],
-            vec![0, (n + 3)],
-            vec![0, (n + 4)],
-            vec![(n + 3), (n + 4)],
+        let scenarii = [
+            (
+                "simple",
+                vec![
+                    vec![2, 4],       // =  n
+                    vec![1, 3],       // = (n + 1)
+                    vec![n, (n + 1)], // = (n + 2) = ((2, 4), (1, 3))
+                ],
+                vec![
+                    vec![2, 4, n],
+                    vec![1, 3, (n + 1)],
+                    vec![n, (n + 1), (n + 2)],
+                    vec![1, 3, n, (n + 2)],
+                    vec![2, 4, (n + 1), (n + 2)],
+                    vec![1, 2, 3, 4, (n + 2)],
+                ],
+            ),
+            (
+                "chain",
+                vec![
+                    vec![0],   // = (n) = (0)
+                    vec![(n)], // = (n + 1) = (0)
+                ],
+                vec![vec![0, (n)], vec![0, (n + 1)], vec![(n), (n + 1)]],
+            ),
         ];
 
         for k in ks {
-            end_to_end_with_recoding_template::<Fr>(
-                &bytes,
-                k,
-                n,
-                recoding_steps.clone(),
-                should_not_be_decodable.clone(),
-            );
+            for (name, steps, should_not_decode) in scenarii.clone() {
+                end_to_end_with_recoding_template::<Fr>(
+                    &bytes,
+                    k,
+                    n,
+                    steps,
+                    should_not_decode,
+                    name,
+                );
+            }
         }
     }