bn254: add simple test

Signed-off-by: Ignacio Hagopian <jsign.uy@gmail.com>

src/bn254/tests.zig

@@ -0,0 +1,27 @@
+const std = @import("std");
+const Fr = @import("fr.zig");
+const parameters = @import("../parameters.zig");
+const poseidon = @import("../poseidon.zig");
+
+test "babyjubjub" {
+    var allocator = std.testing.allocator;
+    var babyjubjub_parameters = try parameters.get_babyjubjub_parameters(allocator);
+    defer babyjubjub_parameters.deinit();
+
+    var instance = poseidon.Poseidon(Fr, 2).init(babyjubjub_parameters);
+
+    var one: u256 = 1;
+    var buf: [32]u8 = undefined;
+    std.mem.writeIntLittle(u256, &buf, one);
+    var nonMontB1: Fr.NonMontgomeryDomainFieldElement = undefined;
+    Fr.fromBytes(&nonMontB1, buf);
+    var b1: Fr.MontgomeryDomainFieldElement = undefined;
+    Fr.toMontgomery(&b1, nonMontB1);
+
+    var res = instance.hash(.{b1});
+
+    Fr.toBytes(&buf, res);
+    const A = std.mem.readInt(u256, &buf, std.builtin.Endian.Little);
+
+    try std.testing.expect(18586133768512220936620570745912940619677854269274689475585506675881198879027 == A);
+}