Account for source not existing

lib/svgeez/builder.rb

@@ -1,6 +1,7 @@
 module Svgeez
   class Builder
     SOURCE_IS_DESTINATION_MESSAGE = "Setting `source` and `destination` to the same path isn't allowed!".freeze
+    SOURCE_DOES_NOT_EXIST = 'Provided `source` folder does not exist.'.freeze
     NO_SVGS_IN_SOURCE_MESSAGE = 'No SVGs were found in `source` folder.'.freeze
 
     attr_reader :source, :destination
@@ -11,6 +12,7 @@ def initialize(options = {})
       @svgo = options.fetch('svgo', false)
 
       raise SOURCE_IS_DESTINATION_MESSAGE if source_is_destination?
+      raise SOURCE_DOES_NOT_EXIST unless source_exists?
     rescue RuntimeError => exception
       logger.error exception.message
       exit
@@ -53,12 +55,12 @@ def logger
       @logger ||= Svgeez.logger
     end
 
-    def source_files_count
-      source_file_paths.length
+    def source_exists?
+      File.directory?(source.folder_path)
     end
 
-    def source_file_paths
-      source.file_paths
+    def source_files_count
+      source.file_paths.length
     end
 
     def source_is_destination?

spec/lib/svgeez/builder_build_spec.rb

@@ -1,14 +1,31 @@
 describe Svgeez::Builder, '#build' do
+  let(:file) { class_double(File) }
   let(:logger) { Svgeez.logger }
   let(:error_message) { "Setting `source` and `destination` to the same path isn't allowed!" }
   let(:warning_message) { 'No SVGs were found in `source` folder.' }
 
   before do
+    allow(File).to receive(:directory?).and_return(true)
+
     allow(logger).to receive(:error)
     allow(logger).to receive(:info)
     allow(logger).to receive(:warn)
   end
 
+  context 'when @source does not exist' do
+    let(:builder) { described_class.new }
+    let(:error_message) { 'Provided `source` folder does not exist.' }
+
+    before do
+      allow(File).to receive(:directory?).and_return(false)
+    end
+
+    it 'logs an error' do
+      expect { builder.build }.to raise_error(SystemExit)
+      expect(logger).to have_received(:error).with(error_message)
+    end
+  end
+
   context 'when @source and @destination are the same' do
     let(:builder) do
       described_class.new(
@@ -18,7 +35,7 @@
     end
 
     it 'logs an error' do
-      expect{ builder.build }.to raise_error(SystemExit)
+      expect { builder.build }.to raise_error(SystemExit)
       expect(logger).to have_received(:error).with(error_message)
     end
   end
@@ -32,7 +49,7 @@
     end
 
     it 'logs an error' do
-      expect{ builder.build }.to raise_error(SystemExit)
+      expect { builder.build }.to raise_error(SystemExit)
       expect(logger).to have_received(:error).with(error_message)
     end
   end
@@ -48,7 +65,6 @@
   end
 
   context 'when @source contains SVG files' do
-    let(:file) { class_double(File) }
     let(:source) { instance_double(Svgeez::Source) }
     let(:source_folder_path) { './spec/fixtures/icons' }