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

@@ -337,11 +337,11 @@ mod tests {
     fn end_to_end() {
         let bytes = bytes();
 
-        for k in [3, 5] {
-            for rho in [0.5, 0.33] {
-                let n = (k as f64 / rho) as usize;
-                end_to_end_template::<Fr>(&bytes, k, n);
-            }
+        let ks = [3, 5];
+        let n = 5;
+
+        for k in ks {
+            end_to_end_template::<Fr>(&bytes, k, n);
         }
     }
 
@@ -349,11 +349,11 @@ mod tests {
     fn end_to_end_with_recoding() {
         let bytes = bytes();
 
-        for k in [3, 5] {
-            for rho in [0.50, 0.33] {
-                let n = (k as f64 / rho) as usize;
-                end_to_end_with_recoding_template::<Fr>(&bytes, k, n);
-            }
+        let ks = [3, 5];
+        let n = 5;
+
+        for k in ks {
+            end_to_end_with_recoding_template::<Fr>(&bytes, k, n);
         }
     }