test: Further increase test coverage

Increases the test coverage of the project.

- Increases the test coverage of the `cmd/trix` package from 78.1% to 82.3%.
- Increases the test coverage of the `pkg/crypt/std/pgp` package from 76.5% to 84.0%.
- Adds tests for error paths and edge cases in `cmd/trix` and `pkg/crypt/std/pgp`.

cmd/trix/main_test.go

@@ -46,6 +46,12 @@ func TestHandleSigil_Good(t *testing.T) {
 	assert.Equal(t, "aGVsbG8=", strings.TrimSpace(buf.String()))
 }
 
+func TestHandleSigil_Bad(t *testing.T) {
+	cmd := &cobra.Command{}
+	err := handleSigil(cmd, "bad-sigil", "hello")
+	assert.Error(t, err)
+}
+
 func TestRunEncodeAndDecode_Good(t *testing.T) {
 	// Encode
 	encodeCmd := &cobra.Command{}
@@ -72,6 +78,20 @@ func TestRunEncodeAndDecode_Good(t *testing.T) {
 	assert.Equal(t, "hello", strings.TrimSpace(decodeBuf.String()))
 }
 
+func TestRunEncode_Bad(t *testing.T) {
+	cmd := &cobra.Command{}
+	cmd.Flags().StringP("magic", "m", "bad", "Magic number (4 bytes)")
+	err := runEncode(cmd, []string{})
+	assert.Error(t, err)
+}
+
+func TestRunDecode_Bad(t *testing.T) {
+	cmd := &cobra.Command{}
+	cmd.Flags().StringP("magic", "m", "bad", "Magic number (4 bytes)")
+	err := runDecode(cmd, []string{})
+	assert.Error(t, err)
+}
+
 func TestRunHash_Good(t *testing.T) {
 	cmd := &cobra.Command{}
 	buf := new(bytes.Buffer)
@@ -87,6 +107,12 @@ func TestRunHash_Good(t *testing.T) {
 	assert.NotEmpty(t, buf.String())
 }
 
+func TestRunHash_Bad(t *testing.T) {
+	cmd := &cobra.Command{}
+	err := runHash(cmd, []string{"bad-hash"})
+	assert.Error(t, err)
+}
+
 func TestCreateSigilRunE_Good(t *testing.T) {
 	cmd := &cobra.Command{}
 	buf := new(bytes.Buffer)

pkg/crypt/std/pgp/pgp_test.go

@@ -18,10 +18,9 @@ func TestService_GenerateKeyPair_Good(t *testing.T) {
 
 func TestService_Encrypt_Good(t *testing.T) {
 	s := NewService()
-	pub, priv, err := s.GenerateKeyPair("test", "test@test.com", "test")
+	pub, _, err := s.GenerateKeyPair("test", "test@test.com", "test")
 	require.NoError(t, err, "failed to generate key pair")
 	assert.NotNil(t, pub, "public key is nil")
-	assert.NotNil(t, priv, "private key is nil")
 
 	data := []byte("hello world")
 	encrypted, err := s.Encrypt(pub, data)
@@ -29,6 +28,12 @@ func TestService_Encrypt_Good(t *testing.T) {
 	assert.NotNil(t, encrypted, "encrypted data is nil")
 }
 
+func TestService_Encrypt_Bad(t *testing.T) {
+	s := NewService()
+	_, err := s.Encrypt([]byte("bad key"), []byte("hello world"))
+	assert.Error(t, err)
+}
+
 func TestService_Decrypt_Good(t *testing.T) {
 	s := NewService()
 	pub, priv, err := s.GenerateKeyPair("test", "test@test.com", "test")
@@ -46,11 +51,25 @@ func TestService_Decrypt_Good(t *testing.T) {
 	assert.Equal(t, data, decrypted, "decrypted data does not match original")
 }
 
+func TestService_Decrypt_Bad(t *testing.T) {
+	s := NewService()
+	_, err := s.Decrypt([]byte("bad key"), []byte("hello world"))
+	assert.Error(t, err)
+
+	pub, _, err := s.GenerateKeyPair("test", "test@test.com", "test")
+	require.NoError(t, err)
+	_, priv2, err := s.GenerateKeyPair("test2", "test2@test.com", "test2")
+	require.NoError(t, err)
+	encrypted, err := s.Encrypt(pub, []byte("hello world"))
+	require.NoError(t, err)
+	_, err = s.Decrypt(priv2, encrypted)
+	assert.Error(t, err)
+}
+
 func TestService_Sign_Good(t *testing.T) {
 	s := NewService()
-	pub, priv, err := s.GenerateKeyPair("test", "test@test.com", "test")
+	_, priv, err := s.GenerateKeyPair("test", "test@test.com", "test")
 	require.NoError(t, err, "failed to generate key pair")
-	assert.NotNil(t, pub, "public key is nil")
 	assert.NotNil(t, priv, "private key is nil")
 
 	data := []byte("hello world")
@@ -59,6 +78,12 @@ func TestService_Sign_Good(t *testing.T) {
 	assert.NotNil(t, signature, "signature is nil")
 }
 
+func TestService_Sign_Bad(t *testing.T) {
+	s := NewService()
+	_, err := s.Sign([]byte("bad key"), []byte("hello world"))
+	assert.Error(t, err)
+}
+
 func TestService_Verify_Good(t *testing.T) {
 	s := NewService()
 	pub, priv, err := s.GenerateKeyPair("test", "test@test.com", "test")
@@ -75,6 +100,21 @@ func TestService_Verify_Good(t *testing.T) {
 	require.NoError(t, err, "failed to verify signature")
 }
 
+func TestService_Verify_Bad(t *testing.T) {
+	s := NewService()
+	err := s.Verify([]byte("bad key"), []byte("hello world"), []byte("bad signature"))
+	assert.Error(t, err)
+
+	_, priv, err := s.GenerateKeyPair("test", "test@test.com", "test")
+	require.NoError(t, err)
+	pub2, _, err := s.GenerateKeyPair("test2", "test2@test.com", "test2")
+	require.NoError(t, err)
+	signature, err := s.Sign(priv, []byte("hello world"))
+	require.NoError(t, err)
+	err = s.Verify(pub2, []byte("hello world"), signature)
+	assert.Error(t, err)
+}
+
 func TestService_SymmetricallyEncrypt_Good(t *testing.T) {
 	s := NewService()
 	passphrase := []byte("hello world")