Refactor the generate todo file tests.

- Refactored the `test_generate_todo` and `test_generate_todo_existing` methods in the `StandardrbTest` class to use a new helper function called `assert_generate_todo`.

test/fixture/standardrb/generate_todo/.standard.yml

@@ -0,0 +1 @@
+ruby_version: 2.6

test/standardrb_test.rb

@@ -2,14 +2,13 @@
 require "open3"
 
 class StandardrbTest < UnitTest
+  FIXTURE_ROOT_FOLDER = "test/fixture"
   TEST_ROOT_FOLDER = "tmp/tests/standardrb"
 
-  def before_setup
-    super
-
-    FileUtils.rm_rf(TEST_ROOT_FOLDER)
-    FileUtils.mkdir_p(TEST_ROOT_FOLDER)
-  end
+  # Initialize the test folder once for all the tests
+  # in this file.
+  FileUtils.rm_rf(TEST_ROOT_FOLDER)
+  FileUtils.mkdir_p(TEST_ROOT_FOLDER)
 
   def test_project_a_failure_output
     stdout, status = run_standardrb("test/fixture/project/a")
@@ -24,38 +23,11 @@ def test_project_a_failure_output
   end
 
   def test_generate_todo
-    FileUtils.rm_rf("tmp/standardrb_generate_todo_test")
-    FileUtils.mkdir_p("tmp/standardrb_generate_todo_test")
-
-    FileUtils.cp("test/fixture/standardrb/generate_todo/useless_assignment.rb", "tmp/standardrb_generate_todo_test/")
-
-    stdout, status = run_standardrb("tmp/standardrb_generate_todo_test", %w[--generate-todo --config ../../config/base.yml])
-
-    # The generate todo returns the Rubocop result which is non-zero
-    # if any linting errors where found.
-    refute status.success?
-    assert stdout.empty?
-
-    assert File.exist?("tmp/standardrb_generate_todo_test/.standard_todo.yml")
-    assert_equal File.read("test/fixture/standardrb/generate_todo/.standard_todo_expected.yml"), File.read("tmp/standardrb_generate_todo_test/.standard_todo.yml")
+    assert_generate_todo("standardrb/generate_todo", "generate_todo", %w[--generate-todo --config ./.standard.yml])
   end
 
   def test_generate_todo_existing
-    config_file = "./.standard.yml"
-    test_folder = File.join(TEST_ROOT_FOLDER, "generate_todo_existing")
-    fixture_folder = "test/fixture/standardrb/generate_todo_existing"
-
-    FileUtils.cp_r(File.join(fixture_folder, "."), test_folder)
-
-    stdout, status = run_standardrb(test_folder, ["--generate-todo", "--config", config_file])
-
-    # The generate todo returns the Rubocop result which is non-zero
-    # if any linting errors where found.
-    refute status.success?
-    assert_equal "", stdout
-
-    assert File.exist?(File.join(test_folder, ".standard_todo.yml"))
-    assert_equal File.read(File.join(test_folder, ".standard_todo_expected.yml")), File.read(File.join(test_folder, ".standard_todo.yml"))
+    assert_generate_todo("standardrb/generate_todo_existing", "generate_todo_existing", %w[--generate-todo --config ./.standard.yml])
   end
 
   def test_project_a_forwards_rubocop_options
@@ -109,7 +81,6 @@ def test_plugins_options
   private
 
   def run_standardrb(cwd, args = [])
-    # REM: Refactor to chdir block?
     og_pwd = Dir.pwd
     Dir.chdir(cwd)
     Open3.capture2(File.join(__dir__, "../exe/standardrb"), *args)
@@ -120,4 +91,21 @@ def run_standardrb(cwd, args = [])
   def assert_same_lines(expected, actual)
     assert_equal expected.split("\n").sort, actual.split("\n").sort
   end
+
+  def assert_generate_todo(fixture_subfolder, test_subfolder, arguments)
+    fixture_folder = File.join(FIXTURE_ROOT_FOLDER, fixture_subfolder)
+    test_folder = File.join(TEST_ROOT_FOLDER, test_subfolder)
+
+    FileUtils.cp_r(File.join(fixture_folder, "."), test_folder)
+
+    stdout, status = run_standardrb(test_folder, arguments)
+
+    # The generate todo returns the Rubocop result which is non-zero
+    # if any linting errors where found.
+    refute status.success?
+    assert stdout.empty?
+
+    assert File.exist?(File.join(test_folder, ".standard_todo.yml"))
+    assert_equal File.read(File.join(test_folder, ".standard_todo_expected.yml")), File.read(File.join(test_folder, ".standard_todo.yml"))
+  end
 end