モーフ用のテストも書いたよ

test/system/tasks_test.rb

@@ -0,0 +1,46 @@
+require "application_system_test_case"
+
+class TasksTest < ApplicationSystemTestCase
+  test "CRUD tasks" do
+    visit tasks_url
+
+    assert_selector "h1", text: "Tasks"
+
+    fill_in "Title", with: "ミルクを買う"
+    click_on "Create Task"
+    assert_text "Task was successfully created."
+    within "#tasks" do
+      assert_text "ミルクを買う"
+    end
+    assert_field "Title", with: ""
+    assert_text "Remains: 1 / Total: 1"
+
+    fill_in "Title", with: "ネギを買う"
+    click_on "Create Task"
+    assert_text "Task was successfully created."
+    within "#tasks" do
+      assert_text "ネギを買う"
+    end
+    assert_field "Title", with:   ""
+    assert_text "Remains: 2 / Total: 2"
+
+    rows = all("#tasks tbody tr")
+    assert_equal 2, rows.size
+    within rows[0] do
+      assert_text "ミルクを買う"
+      assert_text "not yet"
+      click_on "DONE"
+      assert_text "done"
+    end
+    assert_text "Task was successfully updated."
+    assert_text "Remains: 1 / Total: 2"
+
+    within rows[1] do
+      assert_text "ネギを買う"
+      click_on "DELETE"
+    end
+    assert_text "Task was successfully deleted."
+    refute_text "ネギを買う"
+    assert_text "Remains: 0 / Total: 1"
+  end
+end