test: Add unit tests for FilesCountExtractor

spec/uploadcare/rails/services/files_count_extractor_spec.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'uploadcare/rails/services/files_count_extractor'
+
+describe Uploadcare::Rails::FilesCountExtractor, type: :service do
+  describe '.call' do
+    subject { described_class.call(input_str) }
+
+    context 'when input_str is blank' do
+      let(:input_str) { nil }
+
+      it { is_expected.to be_nil }
+    end
+
+    context 'when input_str is present' do
+      context "when it doesn't contain `~` character" do
+        let(:input_str) { 'foobar' }
+
+        it { is_expected.to eq 'foobar' }
+      end
+
+      context 'when it contains a `~` character' do
+        let(:input_str) { 'foo~bar' }
+
+        it { is_expected.to eq 'bar' }
+      end
+    end
+  end
+end