Test invalid mnemonic sentence

Throw error if mnemonic sentence is less
than 12 words or greater than 24 words or
number of words is not a multiple of six or
the contains a word not in wordlist or has
invalid checksum.

Author: vladimirfomene

src/keys/bip39/mod.rs

@@ -122,7 +122,7 @@ impl Mnemonic {
             indices.push(idx);
 
             for j in 0..11 {
-                mnemonic_bits[i * 11 + j] = (idx & (1 << 10 - j)) != 0;
+                mnemonic_bits[i * 11 + j] = (idx & (1 << (10 - j))) != 0;
             }
         }
 
@@ -133,7 +133,7 @@ impl Mnemonic {
         for i in 0..entropy_bytes_len {
             for j in 0..8 {
                 if mnemonic_bits[i * 8 + j] {
-                    entropy[i] += 1 << 7 - j;
+                    entropy[i] += 1 << (7 - j);
                 }
             }
         }
@@ -145,7 +145,7 @@ impl Mnemonic {
         //verify checksum calculated from entropy
         let entropy_bits_len = (words.len() * 32) / 3;
         for (i, &bit) in mnemonic_bits[entropy_bits_len..].iter().enumerate() {
-            if (checksum_byte & (1 << 7 - i) != 0) != bit {
+            if (checksum_byte & (1 << (7 - i)) != 0) != bit {
                 return Err(Error::InvalidChecksum(checksum_byte as usize));
             }
         }
@@ -843,4 +843,50 @@ mod test {
             Err(Error::InvalidEntropyLength(248))
         );
     }
+
+    #[test]
+    fn test_invalid_mnemonic() {
+        //less than 12 words
+        assert_eq!(
+            Mnemonic::parse_in(
+                Language::English,
+                "join fossil bulk soft easily give section spoon divorce ice pilot"
+            ),
+            Err(Error::InvalidWordCount(11))
+        );
+
+        //more than 24 words
+        assert_eq!(Mnemonic::parse_in(Language::English, "area secret six clutch run reject tape
+        ritual soldier mad eagle win impulse found tattoo door culture reject movie grocery resource 
+        thought please conduct gorilla"), Err(Error::InvalidWordCount(25)));
+
+        //not a multiple of six
+        assert_eq!(
+            Mnemonic::parse_in(
+                Language::English,
+                "gorilla convince minor amateur labor advance hungry
+        treat ripple bracket draft wrong found"
+            ),
+            Err(Error::InvalidWordCount(13))
+        );
+
+        //invalid word
+        assert_eq!(
+            Mnemonic::parse_in(
+                Language::English,
+                "here convince minor amateur labor advance hungry treat ripple bracket draft wrong"
+            ),
+            Err(Error::InvalidWord(String::from("here")))
+        );
+
+        //invalid checksum
+        assert_eq!(
+            Mnemonic::parse_in(
+                Language::English,
+                "gorilla convince minor amateur labor advance
+        hungry treat ripple bracket draft gorilla"
+            ),
+            Err(Error::InvalidChecksum(175))
+        );
+    }
 }