Start testing the command line interface

test/uplot/command_test.rb

@@ -1,6 +1,23 @@
 # frozen_string_literal: true
 
+require "tempfile"
 require_relative '../test_helper'
 
 class YouPlotCommandTest < Test::Unit::TestCase
+  def setup
+    @ta = "ta"
+    @stdin = $stdin.dup
+    @stderr = $stderr.dup
+  end
+
+  test :scatter do
+    $stdin  = File.open(File.expand_path("../fixtures/iris.csv", __dir__), "r")
+    Tempfile.new("iris-scatter") do |tmp_file|
+      $stderr = tmp_file
+      YouPlot::Command.new(["scatter", "-H", "-d,", "-t", "IRIS"]).run
+      assert_equal File.read(File.expand_path("../fixtures/iris-scatter.txt", __dir__)), tmp_file.read
+    end
+    $stdin = @stdin
+    $stderr = @stderr
+  end
 end