Add test for the current .po generation behavior

Author: mokagio

.rubocop_todo.yml

@@ -145,6 +145,7 @@ RSpec/FilePath:
     - 'spec/ios_generate_strings_file_from_code_spec.rb'
     - 'spec/ios_l10n_helper_spec.rb'
     - 'spec/ios_merge_strings_files_spec.rb'
+    - 'spec/gp_update_metadata_source_spec.rb'
 
 # Offense count: 8
 # Cop supports --auto-correct.

spec/gp_update_metadata_source_spec.rb

@@ -0,0 +1,56 @@
+require 'spec_helper'
+
+describe Fastlane::Actions::GpUpdateMetadataSourceAction do
+  it 'works' do
+    Dir.mktmpdir do |dir|
+      # Reminder: you can stub Fastlane stuff with calls like
+      # expect(FastlaneCore::UI).to receive(:success).with('Done')
+
+      # 1: Create tmp location for the po file
+      #
+      # Note, can't use StringIO.new because of implementation details:
+      #
+      # Failure/Error: "#{File.dirname(orig_file_path)}/#{File.basename(orig_file_path, '.*')}.tmp"
+      output_path = File.join(dir, 'output.po')
+      # Also note: The file must exist already
+      dummy_text = <<~PO
+        msgctxt "key1"
+        msgid "this value should change"
+        msgstr ""
+        msgctxt "key2"
+        msgid "this value should change"
+        msgstr ""
+      PO
+      File.write(output_path, dummy_text)
+
+      # 2: read a few sources
+      file_1_path = File.join(dir, '1.txt')
+      File.write(file_1_path, 'value 1')
+      file_2_path = File.join(dir, '2.txt')
+      File.write(file_2_path, 'value 2')
+
+      described_class.run(
+        po_file_path: output_path,
+        release_version: '1.23',
+        source_files: {
+          key1: file_1_path,
+          key2: file_2_path
+        }
+      )
+
+      # 3: compare
+      # notice that the new line after each block is added by the conversion
+      expected = <<~PO
+        msgctxt "key1"
+        msgid "value 1"
+        msgstr ""
+
+        msgctxt "key2"
+        msgid "value 2"
+        msgstr ""
+
+      PO
+      expect(File.read(output_path)).to eq(expected)
+    end
+  end
+end