Detect rails as the testing framework if bin/rails exists (#1896)

lib/ruby_lsp/global_state.rb

@@ -104,8 +104,10 @@ def detect_test_library
       if direct_dependency?(/^rspec/)
         "rspec"
       # A Rails app may have a dependency on minitest, but we would instead want to use the Rails test runner provided
-      # by ruby-lsp-rails.
-      elsif direct_dependency?(/^rails$/)
+      # by ruby-lsp-rails. A Rails app doesn't need to depend on the rails gem itself, individual components like
+      # activestorage may be added to the gemfile so that other components aren't downloaded. Check for the presence
+      #  of bin/rails to support these cases.
+      elsif File.exist?(File.join(workspace_path, "bin/rails"))
         "rails"
       # NOTE: Intentionally ends with $ to avoid mis-matching minitest-reporters, etc. in a Rails app.
       elsif direct_dependency?(/^minitest$/)

test/global_state_test.rb

@@ -33,14 +33,16 @@ def test_detects_dependencies_in_gemspecs
       assert(GlobalState.new.direct_dependency?(/^prism$/))
     end
 
-    def test_detects_rails_if_both_rails_and_minitest_are_present
-      stub_dependencies("minitest" => "1.2.3", "rails" => "1.2.3")
+    def test_detects_rails_if_minitest_is_present_and_bin_rails_exists
+      stub_dependencies("minitest" => "1.2.3")
+      File.expects(:exist?).with("#{Dir.pwd}/bin/rails").once.returns(true)
 
       assert_equal("rails", GlobalState.new.test_library)
     end
 
     def test_detects_rspec_if_both_rails_and_rspec_are_present
-      stub_dependencies("rspec" => "1.2.3", "rails" => "1.2.3")
+      stub_dependencies("rspec" => "1.2.3")
+      File.expects(:exist?).never
 
       assert_equal("rspec", GlobalState.new.test_library)
     end