错误：
“User.count”未更改-1。预期：实际人数：2人
当我试用它的时候，它确实可以在应用程序上工作。但是，当我尝试测试它的时候，它会显示这个错误：

用户控制器测试

test "should destroy user" do
    # Log in as an admin user
    post login_path, params: { session: { email: "example@railstutorial.org", password: 'foobar', admin: true } }

    # Set the user variable explicitly
    @user = users(:manon)
    assert_difference("User.count", -1) do
      delete user_url(@user)
    end

    assert_redirected_to users_url

    # Verify that the user was actually deleted from the database
    assert_nil User.find_by(id: @user.id)
  end

用户控制器

class UsersController < ApplicationController
  before_action :logged_in_user, only: [:index,:edit, :update, :destroy]
  before_action :correct_user, only: [:edit, :update]
  before_action :admin_user, only: :destroy

  # GET /users or /users.json
  def index
    @users = User.all
  end

  # GET /users/1 or /users/1.json
  def show
    @user = User.find(params[:id])
    # debugger
  end

  # GET /users/new
  def new
    @user = User.new
  end

  # GET /users/1/edit
  def edit
  end

  # POST /users or /users.json
  def create
    @user = User.new(user_params)

    respond_to do |format|
      if @user.save
        log_in @user
        format.html { redirect_to user_url(@user), notice: "Welcome to the Sample App" }
        format.json { render :show, status: :created, location: @user }
      else
        format.html { render :new, status: :unprocessable_entity }
        format.json { render json: @user.errors, status: :unprocessable_entity }
      end
    end
  end

  def edit
    @user = User.find(params[:id])
  end

  # def update
  #   @user = User.find(params[:id])
  #   if @user.update(user_params)
  #     # Handle a successful update.
  #   else
  #     render 'edit'
  #   end
  # end

  # PATCH/PUT /users/1 or /users/1.json
  def update
    if @user.update(user_params)
      flash[:success] = "Profile Updated"
      redirect_to user_url(@user)
    else
      flash.now[:error] = "There was an error updating your profile."
      render :edit, status: :unprocessable_entity
    end
  end

  # DELETE /users/1 or /users/1.json
  def destroy
    User.find(params[:id]).destroy
    flash[:success] = "User deleted"
    redirect_to users_url
  end
  

  #show micropost for the user
  def show
    @user = User.find(params[:id])
    @micropost = @user.microposts.first
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_user
      @user = User.find(params[:id])
    end

    # Only allow a list of trusted parameters through.
    def user_params
      params.require(:user).permit(:name, :email, :password, :password_confirmation)
    end

    # Before filters
# Confirms a logged-in user.
  def logged_in_user
    unless logged_in?
      store_location
      flash[:danger] = "Please log in."
      redirect_to login_url
    end
  end

  # Confirms the correct user.
  def correct_user
    @user = User.find(params[:id])
    redirect_to(root_url) unless current_user?(@user)
  end

  # Confirms an admin user.
  def admin_user
    redirect_to(root_url) unless current_user.admin?
  end
end

会话助手

module SessionsHelper
    # Logs in the given user.
    def log_in(user)
        session[:user_id] = user.id
    end

    # Remembers a user in a persistent session.
    def remember(user)
        user.remember
        cookies.permanent.signed[:user_id] = user.id
        cookies.permanent[:remember_token] = user.remember_token
    end

    # Returns the user corresponding to the remember token cookie.
    def current_user
        if (user_id = session[:user_id])
            @current_user ||= User.find_by(id: user_id)
        elsif (user_id = cookies.signed[:user_id])
            user = User.find_by(id: user_id)
            if user && user.authenticated?(cookies[:remember_token])
                log_in user
                @current_user = user
            end
        end
    end

    # Returns true if the given user is the current user.
    def current_user?(user)
        user && user == current_user
    end

    # Returns true if the user is logged in, false otherwise.
    def logged_in?
        !current_user.nil?
    end

    # Forgets a persistent session.
    def forget(user)
        user.forget
        cookies.delete(:user_id)
        cookies.delete(:remember_token)
    end

    # Logs out the current user.
    def log_out
        forget(current_user)
        session.delete(:user_id)
        @current_user
    end

    # Redirects to stored location (or to the default).
    def redirect_back_or(default)
        redirect_to(session[:forwarding_url] || default) 
        session.delete(:forwarding_url)
    end

  # Stores the URL trying to be accessed.
  def store_location
    session[:forwarding_url] = request.url if request.get?
  end
end