Add code to inflate test repo and test extraction

spec/foobara/extract_repo_spec.rb

@@ -1,4 +1,39 @@
 RSpec.describe Foobara::ExtractRepo do
+  let(:repo_path) do
+    "#{__dir__}/../fixtures/test_repo"
+  end
+  let(:output_dir) do
+    # TODO: make this an input to ExtractRepo
+    "#{ENV.fetch("HOME", nil)}/tmp/extract/test_repo"
+  end
+
+  def inflate_test_repo
+    Dir.chdir(File.dirname(repo_path)) do
+      unless Dir.exist?("extract_repo")
+        `tar zxvf test_repo.tar.gz`
+        unless $?.exitstatus == 0
+          raise "Failed to inflate test repo"
+        end
+      end
+    end
+  end
+
+  before do
+    inflate_test_repo
+  end
+
+  context "when extracting a file that was moved" do
+    let(:paths) { %w[new_name] }
+
+    it "can follow the file's history" do
+      ExtractRepo.run!(repo_path, paths)
+
+      Dir.chdir output_dir do
+        expect(File).to exist("new_name/new_name.txt")
+      end
+    end
+  end
+
   it "has a version number" do
     expect(Foobara::ExtractRepo::VERSION).to_not be_nil
   end