fix: the string source should error if the string is empty

keys/errors.go

@@ -29,4 +29,7 @@ var (
 
 	// ErrEmptyFilePath represents an error for when an expected file path is an empty string
 	ErrEmptyFilePath = ErrGetKeySource{"file path cannot be empty"}
+
+	// ErrEmptyString represents an error for when an expected string should contain a public key
+	ErrEmptyString = ErrGetKeySource{"string cannot be empty"}
 )

keys/source.go

@@ -87,5 +87,8 @@ type StringSource string
 
 // Get converts the string to a byte slice
 func (source StringSource) Get(ctx context.Context) ([]byte, error) {
+	if source == "" {
+		return nil, ErrEmptyString
+	}
 	return []byte(source), nil
 }

keys/source_test.go

@@ -120,6 +120,12 @@ func TestStringSource(t *testing.T) {
 			expectedBytes: []byte("barbaz"),
 			expectedErr:   nil,
 		},
+		{
+			name:          "when source is empty",
+			source:        keys.StringSource(""),
+			expectedBytes: nil,
+			expectedErr:   keys.ErrEmptyString,
+		},
 	}
 	for _, c := range cases {
 		t.Run(c.name, func(t *testing.T) {