add test is not working

Cargo.toml

@@ -48,6 +48,7 @@ serde = { version = "1.0", default-features = false, optional = true, features =
 packed_simd = { version = "0.3", features = ["into_bits"], optional = true }
 zeroize = { version = "1", default-features = false }
 engine25519-as = { path="../engine25519-as", default-features = false, features = [] }
+rand = { version = "0.7" }
 
 [features]
 nightly = ["subtle/nightly"]

src/field.rs

@@ -464,6 +464,7 @@ mod test {
         use std::io::prelude::*;
         use std::path::Path;
         use engine25519_as::*;
+        use rand::Rng;
 
         fn write_helper(file: &mut File, elem: FieldElement) {
             let elem_bytes = elem.to_bytes();
@@ -476,10 +477,10 @@ mod test {
             let _ = write!(file, " ");*/
         }
 
-        let a = FieldElement::one();
+        let path = Path::new("test_vectors.bin");
-        let b = FieldElement::minus_one();
+        let mut file = File::create(&path).unwrap();
-        let q = &a + &b;
 
+        fn test_add(mut file: &mut File) {
             let mcode = assemble_engine25519!(
                 start:
                     add %2, %0, %1
@@ -488,9 +489,6 @@ mod test {
                     fin
             );
 
-        let path = Path::new("test_vectors.bin");
-        let mut file = File::create(&path).unwrap();
-
             // insert machine code
             // Metadata record:
             //   0x0 0x56454354   "VECT" - indicates a valid vector set
@@ -512,9 +510,9 @@ mod test {
                                 | (mcode_len & 0xFFFF)
                                 ) as u32)
                                 .to_le_bytes() ); // load address 0 + code length
-        let _ = file.write(&( ((2 & 0x1F) << 27
+            let _ = file.write(&( ((2 & 0x1F) << 27 // number of source registers per test
-                             | (0 & 0xF) << 23
+                                | (0 & 0xF) << 23   // register window to use
-                             | (1 & 0x3F_FFFF)
+                                | (5 & 0x3F_FFFF)   // number of tests
                                 ) as u32)
                                 .to_le_bytes() ); // 2 registers, window 0, 1 vector
             // the actual microcode
@@ -528,10 +526,27 @@ mod test {
             }
 
             // test vectors
+            // 1 plus -1 = 0 -> this works overflow path
+            let a = FieldElement::one();
+            let b = FieldElement::minus_one();
+            let q = &a + &b;
+
             write_helper(&mut file, a);
             write_helper(&mut file, b);
             write_helper(&mut file, q);
 
+            // four random numbers
+            for _ in 0..4 {
+                let a = FieldElement::from_bytes(&rand::thread_rng().gen::<[u8; 32]>());
+                let b = FieldElement::from_bytes(&rand::thread_rng().gen::<[u8; 32]>());
+                let q = &a + &b;
+                write_helper(&mut file, a);
+                write_helper(&mut file, b);
+                write_helper(&mut file, q);
+            }
+        }
+
+        test_add(&mut file);
         // end sequence
         let _ = file.write(&(0xFFFF_FFFF as u32).to_le_bytes());
     }

src/lib.rs

@@ -61,6 +61,7 @@ pub(crate) mod macros;
 
 #[macro_use]
 extern crate engine25519_as;
+extern crate rand;
 
 //------------------------------------------------------------------------
 // curve25519-dalek public modules