Ensure directory is a git root

lib/mosaik/commands/extract.rb

@@ -41,11 +41,13 @@ def call
         # Extract structural coupling information and add to graph
         Extractors::Structural
           .new(options, graph)
+          .tap(&:validate)
           .call
 
         # Extract evolutionary (logical and contributor) coupling information and add to graph
         Extractors::Evolution
           .new(options, graph)
+          .tap(&:validate)
           .call
       end
 

lib/mosaik/extractor.rb

@@ -12,6 +12,8 @@ def initialize(options, graph)
       @graph = graph
     end
 
+    def validate; end
+
     def call
       raise NotImplementedError
     end

lib/mosaik/extractors/evolution.rb

@@ -6,6 +6,10 @@ module Extractors
     # Evolutionary (logical and contributor) coupling extraction
     #
     class Evolution < Extractor
+      def validate
+        raise OptionError, "directory is not a git repository" unless File.directory?(File.join(options[:directory], ".git"))
+      end
+
       def call
         return unless options[:logical].positive? || options[:contributor].positive?
 

spec/mosaik/extractors/evolution_spec.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+RSpec.describe MOSAIK::Extractors::Evolution do
+  subject(:extractor) { described_class.new(options, graph) }
+
+  let(:options) { { directory: MOSAIK.root, logical: 1, contributor: 1 } }
+  let(:graph) { build(:graph) }
+
+  let(:configuration) { build(:configuration) }
+
+  describe "#validate" do
+    it "does not raise an error" do
+      expect { extractor.validate }.not_to raise_error
+    end
+
+    context "when the directory is not a git repository root" do
+      let(:options) { { directory: "/tmp" } }
+
+      it "raises an error" do
+        expect { extractor.validate }.to raise_error MOSAIK::OptionError, "directory is not a git repository"
+      end
+    end
+  end
+end