Merge rust-bitcoin/rust-bitcoin#4012: primitives: Add tests to `block.rs`

ff3b3ddb67 Add a test for Header size (Jamil Lambert, PhD)
0df15d5cfd Add version test (Jamil Lambert, PhD)
927251ef8e Expand version signalling test (Jamil Lambert, PhD)

Pull request description:

  Running `cargo mutants` on `primitives/src/block.rs` found multiple mutants.

  Add tests to kill the mutants and replace one verbosely written out sum with the result.

ACKs for top commit:
  apoelstra:
    ACK ff3b3ddb675446fd21f3f7488749fc7fb26c7ef2; successfully ran local tests
  tcharding:
    ACK ff3b3ddb67

Tree-SHA512: a30cabf699b5c1c5f1b3507385f1041795316c8a5739454b219719aafe24d1f10e20b69b3cb2330290b7df71d5fedfd0d353b63404f47bef9476e0be2b115295

primitives/src/block.rs

@@ -365,6 +365,8 @@ mod tests {
     fn version_is_signalling() {
         let version = Version::from_consensus(0b00100000000000000000000000000010);
         assert!(Version::is_signalling_soft_fork(&version, 1));
+        let version = Version::from_consensus(0b00110000000000000000000000000000);
+        assert!(Version::is_signalling_soft_fork(&version, 28));
     }
 
     #[test]
@@ -372,4 +374,34 @@ mod tests {
         let version = Version::from_consensus(0b00100000000000000000000000000010);
         assert!(!Version::is_signalling_soft_fork(&version, 0));
     }
+
+    #[test]
+    fn version_to_consensus() {
+        let version = Version::from_consensus(1234567890);
+        assert_eq!(version.to_consensus(), 1234567890);
+    }
+
+    // Check that the size of the header consensus serialization matches the const SIZE value
+    #[test]
+    fn header_size() {
+        let header = Header {
+            version: Version::ONE,
+            prev_blockhash: BlockHash::from_byte_array([0x99; 32]),
+            merkle_root: TxMerkleNode::from_byte_array([0x77; 32]),
+            time: 2,
+            bits: CompactTarget::from_consensus(3),
+            nonce: 4,
+        };
+
+        // Calculate the size of the block header in bytes from the sum of the serialized lengths
+        // it's fields: version, prev_blockhash, merkle_root, time, bits, nonce.
+        let header_size = header.version.to_consensus().to_le_bytes().len()
+            + header.prev_blockhash.as_byte_array().len()
+            + header.merkle_root.as_byte_array().len()
+            + header.time.to_le_bytes().len()
+            + header.bits.to_consensus().to_le_bytes().len()
+            + header.nonce.to_le_bytes().len();
+
+        assert_eq!(header_size, Header::SIZE);
+    }
 }