Add a test for edge cases

Secp256k1.xs

@@ -59,6 +59,10 @@ void secp256k1_perl_replace_signature(secp256k1_perl *perl_ctx, secp256k1_ecdsa_
 
 secp256k1_perl* ctx_from_sv(SV* self)
 {
+	if (!(sv_isobject(self) && sv_derived_from(self, "Bitcoin::Secp256k1"))) {
+		croak("calling Bitcoin::Secp256k1 methods is only valid in object context");
+	}
+
 	return (secp256k1_perl*) SvIV(SvRV(self));
 }
 
@@ -88,7 +92,7 @@ new(classname)
 		SPAGAIN;
 
 		if (count != 1) {
-			croak("Calling Bytes::Random::Secure::random_bytes went wrong in Bitcoin::Secp256k1::new");
+			croak("calling Bytes::Random::Secure::random_bytes went wrong in Bitcoin::Secp256k1::new");
 		}
 
 		tmp = POPs;

t/edge-cases.t

@@ -0,0 +1,60 @@
+use Test2::V0;
+use Bitcoin::Secp256k1;
+
+use lib 't/lib';
+use Secp256k1Test;
+
+################################################################################
+# This tests if all foreseeable edge cases are handled correctly
+################################################################################
+
+my $secp = Bitcoin::Secp256k1->new;
+my %t = Secp256k1Test->test_data;
+
+subtest 'should die on constructor with arguments' => sub {
+	my $ex = dies { Bitcoin::Secp256k1->new('argument') };
+	like $ex, qr/\QUsage: Bitcoin::Secp256k1::new(classname)\E/, 'exception ok';
+};
+
+subtest 'should die on low level methods without constructed object' => sub {
+	my $ex = dies { Bitcoin::Secp256k1->_pubkey };
+	like $ex, qr/calling Bitcoin::Secp256k1 methods is only valid in object context/, 'exception ok';
+};
+
+subtest 'should die on high level methods without constructed object' => sub {
+	my $ex = dies { Bitcoin::Secp256k1->create_public_key("\x12" x 32) };
+	like $ex, qr/calling Bitcoin::Secp256k1 methods is only valid in object context/, 'exception ok';
+};
+
+subtest 'should die with reference private key' => sub {
+	my $ex = dies { $secp->create_public_key([]) };
+	like $ex, qr/requires a 32-byte secret key/, 'exception ok';
+};
+
+subtest 'should die with invalid length private key' => sub {
+	my $ex;
+
+	$ex = dies { $secp->create_public_key("\x12" x 31) };
+	like $ex, qr/requires a 32-byte secret key/, 'too short ok';
+
+	$ex = dies { $secp->create_public_key("\x12" x 33) };
+	like $ex, qr/requires a 32-byte secret key/, 'too long ok';
+};
+
+subtest 'should die with invalid public key' => sub {
+	my $ex = dies { $secp->verify_digest("\x12" x 65, $t{sig}, "\x12" x 32) };
+	like $ex, qr/the input does not appear to be a valid public key/, 'exception ok';
+};
+
+subtest 'should die with invalid signature' => sub {
+	my $ex = dies { $secp->verify_digest($t{pubkey}, "\x12" x 65, "\x12" x 32) };
+	like $ex, qr/the input does not appear to be a valid signature/, 'exception ok';
+};
+
+subtest 'should die with invalid digest' => sub {
+	my $ex = dies { $secp->verify_digest($t{pubkey}, $t{sig}, "\x12" x 35) };
+	like $ex, qr/requires a 32-byte message hash/, 'exception ok';
+};
+
+done_testing;
+