1 files changed, 37 insertions, 0 deletions
diff --git a/src/crypto/elliptic/internal/fiat/p521_test.go b/src/crypto/elliptic/internal/fiat/p521_test.go
new file mode 100644
index 0000000..661bde3
--- /dev/null
+++ b/src/crypto/elliptic/internal/fiat/p521_test.go
@@ -0,0 +1,37 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fiat_test
+
+import (
+	"crypto/elliptic/internal/fiat"
+	"crypto/rand"
+	"testing"
+)
+
+func p521Random(t *testing.T) *fiat.P521Element {
+	buf := make([]byte, 66)
+	if _, err := rand.Read(buf); err != nil {
+		t.Fatal(err)
+	}
+	buf[65] &= 1
+	e, err := new(fiat.P521Element).SetBytes(buf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return e
+}
+
+func TestP521Invert(t *testing.T) {
+	a := p521Random(t)
+	inv := new(fiat.P521Element).Invert(a)
+	one := new(fiat.P521Element).Mul(a, inv)
+	if new(fiat.P521Element).One().Equal(one) != 1 {
+		t.Errorf("a * 1/a != 1; got %x for %x", one.Bytes(), a.Bytes())
+	}
+	inv.Invert(new(fiat.P521Element))
+	if new(fiat.P521Element).Equal(inv) != 1 {
+		t.Errorf("1/0 != 0; got %x", inv.Bytes())
+	}
+}