Fix tests by mocking returned checksum

Author: zachfeldman

spec/erb_lint/cache_spec.rb

@@ -42,8 +42,11 @@
       f.write(cache_file_content)
     end
 
-    allow(::RuboCop::ConfigLoader).to(receive(:load_file).and_call_original)
-    allow(::RuboCop::ConfigLoader).to(receive(:read_file).and_return(rubocop_yml))
+    digest_sha1_double = instance_double(Digest::SHA1)
+    allow(Digest::SHA1).to receive(:new).and_return(digest_sha1_double)
+    allow(digest_sha1_double).to receive(:hexdigest).and_return(checksum)
+    allow(digest_sha1_double).to receive(:update).and_return(true)
+    allow(digest_sha1_double).to receive(:file).and_return(true)
   end
 
   describe "#get" do