Add tests for runner#test_files method

railties/lib/rails/test_unit/runner.rb

@@ -94,13 +94,6 @@ module Rails
       @options[:backtrace]
     end
 
-    private
-    def run_tests
-      test_files.to_a.each do |file|
-        require File.expand_path file
-      end
-    end
-
     def test_files
       return [@options[:filename]] if @options[:filename]
       if @options[:patterns]
@@ -111,6 +104,13 @@ module Rails
       Rake::FileList[pattern]
     end
 
+    private
+    def run_tests
+      test_files.to_a.each do |file|
+        require File.expand_path file
+      end
+    end
+
     def test_methods
       methods_map = []
       suites = Minitest::Runnable.runnables.shuffle

railties/test/test_unit/runner_test.rb

@@ -70,6 +70,9 @@ class TestUnitTestRunnerTest < ActiveSupport::TestCase
     assert_equal ["#{__dir__}/**/*_test.rb", "#{application_dir}/**/*_test.rb"], options[:patterns]
     assert_nil options[:filename]
     assert_nil options[:line]
+
+    runner = Rails::TestRunner.new(options)
+    assert runner.test_files.size > 0
   end
 
   test "run multiple files and run one file by line" do
@@ -79,5 +82,16 @@ class TestUnitTestRunnerTest < ActiveSupport::TestCase
     assert_equal ["#{__dir__}/**/*_test.rb"], options[:patterns]
     assert_equal __FILE__, options[:filename]
     assert_equal line, options[:line]
+
+    runner = Rails::TestRunner.new(options)
+    assert_equal [__FILE__], runner.test_files, 'Only returns the file that running by line'
+  end
+
+  test "running multiple files passing line number" do
+    line = __LINE__
+    options = @options.parse(["foobar.rb:8", "#{__FILE__}:#{line}"])
+
+    assert_equal __FILE__, options[:filename], 'Returns the last file'
+    assert_equal line, options[:line]
   end
 end