diff --git a/poseidon-lengths/README.md b/poseidon-lengths/README.md
new file mode 100644
index 0000000..ca1343d
--- /dev/null
+++ b/poseidon-lengths/README.md
@@ -0,0 +1,25 @@
+# poseidon-lengths test
+
+Test to check the output of the Poseidon Hash implementations in Go and Rust for the cases when the BigInt outputed is of 31 bytes.
+
+- Go
+```
+> go test
+
+bigint 166341157454475665850184286625226909090143669024322546717713937140175961129
+length 31
+bytes [94 37 80 113 132 94 199 232 119 124 206 119 0 59 128 138 249 85 43 37 236 41 18 110
+ 214 23 182 6 121 124 41]
+hex 5e255071845ec7e8777cce77003b808af9552b25ec29126ed617b606797c29
+```
+
+- Rust
+```
+> cargo test -- --nocapture
+
+bigint "166341157454475665850184286625226909090143669024322546717713937140175961129"
+length 31
+bytes [94, 37, 80, 113, 132, 94, 199, 232, 119, 124, 206, 119, 0, 59, 128, 138, 249, 85, 43
+, 37, 236, 41, 18, 110, 214, 23, 182, 6, 121, 124, 41]
+hex "5e255071845ec7e8777cce77003b808af9552b25ec29126ed617b606797c29"
+```
diff --git a/poseidon-lengths/go/go.mod b/poseidon-lengths/go/go.mod
new file mode 100644
index 0000000..97b9176
--- /dev/null
+++ b/poseidon-lengths/go/go.mod
@@ -0,0 +1,5 @@
+module poseidon-lengths
+
+go 1.14
+
+require github.com/iden3/go-iden3-crypto v0.0.4
diff --git a/poseidon-lengths/go/go.sum b/poseidon-lengths/go/go.sum
new file mode 100644
index 0000000..8b2a4d4
--- /dev/null
+++ b/poseidon-lengths/go/go.sum
@@ -0,0 +1,16 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dchest/blake512 v1.0.0/go.mod h1:FV1x7xPPLWukZlpDpWQ88rF/SFwZ5qbskrzhLMB92JI=
+github.com/ethereum/go-ethereum v1.8.27/go.mod h1:PwpWDrCLZrV+tfrhqqF6kPknbISMHaJv9Ln3kPCZLwY=
+github.com/iden3/go-iden3-crypto v0.0.4 h1:rGQEFBvX6d4fDxqkQTizVq5UefB+xdZAg8j5FQ6uv6g=
+github.com/iden3/go-iden3-crypto v0.0.4/go.mod h1:LLcgB7DLWAUs+8eBSKne+ZHy5z7xtAmlYlEz0M9M8gE=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20190621222207-cc06ce4a13d4 h1:ydJNl0ENAG67pFbB+9tfhiL2pYqLhfoaZFw/cjLhY4A=
+golang.org/x/crypto v0.0.0-20190621222207-cc06ce4a13d4/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d h1:+R4KGOnez64A81RvjARKc4UT5/tI9ujCIVX+P5KiHuI=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
diff --git a/poseidon-lengths/go/length_test.go b/poseidon-lengths/go/length_test.go
new file mode 100644
index 0000000..4ec6624
--- /dev/null
+++ b/poseidon-lengths/go/length_test.go
@@ -0,0 +1,25 @@
+package main
+
+import (
+	"encoding/hex"
+	"fmt"
+	"testing"
+
+	"github.com/iden3/go-iden3-crypto/poseidon"
+)
+
+func TestLen(t *testing.T) {
+	m := []byte("45")
+	h, err := poseidon.HashBytes(m)
+	if err != nil {
+		t.Fatal(err)
+	}
+	fmt.Println("bigint", h.String())
+	fmt.Println("length", len(h.Bytes()))
+	fmt.Println("bytes", h.Bytes())
+	fmt.Println("hex", hex.EncodeToString(h.Bytes()))
+	if len(h.Bytes()) != 31 {
+		t.Fatal("expected 31 bytes")
+	}
+
+}
diff --git a/poseidon-lengths/rs/.gitignore b/poseidon-lengths/rs/.gitignore
new file mode 100644
index 0000000..96ef6c0
--- /dev/null
+++ b/poseidon-lengths/rs/.gitignore
@@ -0,0 +1,2 @@
+/target
+Cargo.lock
diff --git a/poseidon-lengths/rs/Cargo.toml b/poseidon-lengths/rs/Cargo.toml
new file mode 100644
index 0000000..6da4022
--- /dev/null
+++ b/poseidon-lengths/rs/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "rs"
+version = "0.0.1"
+authors = ["arnaucube <root@arnaucube.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+poseidon-rs = "0.0.2"
+rustc-hex = "1.0.0"
diff --git a/poseidon-lengths/rs/src/lib.rs b/poseidon-lengths/rs/src/lib.rs
new file mode 100644
index 0000000..f5d51f0
--- /dev/null
+++ b/poseidon-lengths/rs/src/lib.rs
@@ -0,0 +1,17 @@
+#[cfg(test)]
+mod tests {
+    use poseidon_rs::Poseidon;
+    use rustc_hex::ToHex;
+
+    #[test]
+    fn test_output_size() {
+        let poseidon = Poseidon::new();
+        let msg = "45";
+        let h = poseidon.hash_bytes(msg.as_bytes().to_vec()).unwrap();
+        println!("bigint {:?}", h.to_string());
+        println!("length {:?}", h.to_bytes_be().1.len());
+        println!("bytes {:?}", h.to_bytes_be().1);
+        assert_eq!(h.to_bytes_be().1.len(), 31);
+        println!("hex {:?}", h.to_bytes_be().1.to_hex());
+    }
+}