feat: initial commit

internal/anubis/pow_test.go

@@ -0,0 +1,58 @@
+package anubis
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+func TestSolveProducesLeadingZeros(t *testing.T) {
+	cases := []struct {
+		randomData string
+		difficulty int
+	}{
+		{"abc123", 1},
+		{"deadbeefcafebabe", 2},
+		{"root-me-scoreboard", 3},
+		{"odd-difficulty-check", 5},
+	}
+
+	for _, tc := range cases {
+		hash, nonce := Solve(tc.randomData, tc.difficulty)
+
+		// The hash must have exactly `difficulty` leading '0' hex digits.
+		if got := leadingZeroDigits(hash); got < tc.difficulty {
+			t.Errorf("Solve(%q, %d): hash %s has %d leading zeros, want >= %d",
+				tc.randomData, tc.difficulty, hash, got, tc.difficulty)
+		}
+
+		// And it must be reproducible: SHA-256(randomData + nonce) == hash.
+		want := sha256.Sum256([]byte(tc.randomData + strconv.FormatUint(nonce, 10)))
+		if hex.EncodeToString(want[:]) != hash {
+			t.Errorf("Solve(%q, %d): hash not reproducible from nonce %d",
+				tc.randomData, tc.difficulty, nonce)
+		}
+	}
+}
+
+func TestSolveFindsSmallestNonce(t *testing.T) {
+	// Brute the expected smallest nonce independently and compare.
+	const data, diff = "smallest", 2 // difficulty 2 == first byte zero
+	var want uint64
+	for {
+		sum := sha256.Sum256([]byte(data + strconv.FormatUint(want, 10)))
+		if sum[0] == 0 {
+			break
+		}
+		want++
+	}
+	if _, nonce := Solve(data, diff); nonce != want {
+		t.Errorf("Solve smallest nonce = %d, want %d", nonce, want)
+	}
+}
+
+func leadingZeroDigits(hexHash string) int {
+	return len(hexHash) - len(strings.TrimLeft(hexHash, "0"))
+}