[Test a method that writes to a file] Use RSpec to call a method that writes to a file and then test the contents of the file, all while ensuring that each created file immediately gets deleted after testing (i.e. temp file)

test_file_contents.rb

RSpec.describe SomeClass do
  describe '.some_method_that_writes_to_a_file' do
    around(:example) do |example|
      Dir.mktmpdir do |dir|
        Dir.chdir(dir) do
          example.run # Write file to a tmp directory that then gets deleted after each example
        end
      end
    end

    it 'has content' do
      subject.some_method_that_writes_to_a_file
      text = File.read('some_file.txt')
      expect(text).to eql('Hello world!')
    end
  end
end

write_to_tmp_dir.rb

RSpec.describe SomeClass do
  let(:tmpdir) { Dir.mktmpdir }
  let(:csv_path) { File.join(tmpdir, SomeClass::DEFAULT_CSV_FILENAME) }
  let(:perform_now) { described_class.perform_now }
  let(:perform_later) { described_class.perform_later }

  before(:example) do
    # Generate files in a tmp directory (instead of, say, a downloads/ directory)
    stub_const('SomeClass', SomeClass)
    stub_const('SomeClass::DEFAULT_CSV_FILEPATH', csv_path)
  end

  after(:example) do
    # Cleanup tmp directory
    FileUtils.rm_rf(tmpdir)
  end
  
  it 'creates a new file' do
    # Test method that specifically writes to the csv_path
  end
end