diff --git a/prover.go b/prover.go
index dee889f..21fe479 100644
--- a/prover.go
+++ b/prover.go
@@ -2,6 +2,7 @@ package gocircomprover
 
 import (
 	"crypto/rand"
+	"fmt"
 	"math/big"
 
 	bn256 "github.com/ethereum/go-ethereum/crypto/bn256/cloudflare"
@@ -101,3 +102,32 @@ func Prove(pk *ProvingKey, w Witness) (*Proof, []*big.Int, error) {
 
 	return &proof, pubSignals, nil
 }
+
+func calculateH(pk *ProvingKey, w Witness) []*big.Int {
+	m := pk.DomainSize
+	polAT := arrayOfZeroes(m)
+	polBT := arrayOfZeroes(m)
+	polCT := arrayOfZeroes(m)
+
+	for i := 0; i < pk.NVars; i++ {
+		for j, _ := range pk.PolsA[i] {
+			polAT[j] = FAdd(polAT[j], FMul(w[i], pk.PolsA[i][j]))
+			fmt.Println(polAT[j])
+		}
+		for j, _ := range pk.PolsB[i] {
+			polBT[j] = FAdd(polBT[j], FMul(w[i], pk.PolsB[i][j]))
+		}
+		for j, _ := range pk.PolsC[i] {
+			polCT[j] = FAdd(polCT[j], FMul(w[i], pk.PolsC[i][j]))
+		}
+	}
+	polAS := ifft(polAT)
+	polBS := ifft(polBT)
+
+	polABS := PolynomialMul(polAS, polBS)
+	polCS := ifft(polCT)
+	polABCS := PolynomialSub(polABS, polCS)
+
+	hS := polABCS[m:]
+	return hS
+}
diff --git a/prover_test.go b/prover_test.go
new file mode 100644
index 0000000..dfa6416
--- /dev/null
+++ b/prover_test.go
@@ -0,0 +1,35 @@
+package gocircomprover
+
+import (
+	"fmt"
+	"io/ioutil"
+	"math/big"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestProve(t *testing.T) {
+	provingKeyJson, err := ioutil.ReadFile("testdata/provingkey.json")
+	require.Nil(t, err)
+	pk, err := ParseProvingKey(provingKeyJson)
+	require.Nil(t, err)
+
+	fmt.Println("polsA", pk.PolsA)
+	fmt.Println("polsB", pk.PolsB)
+	fmt.Println("polsC", pk.PolsC)
+
+	witnessJson, err := ioutil.ReadFile("testdata/witness.json")
+	require.Nil(t, err)
+	w, err := ParseWitness(witnessJson)
+	require.Nil(t, err)
+
+	fmt.Println("w", w)
+	assert.Equal(t, Witness{big.NewInt(1), big.NewInt(33), big.NewInt(3), big.NewInt(11)}, w)
+
+	proof, pubSignals, err := Prove(pk, w)
+	assert.Nil(t, err)
+	fmt.Println("proof", proof)
+	fmt.Println("pubSignals", pubSignals)
+}