rspec test failed for params

Question

i'm new to rails , i'm tring to write spec test for controller method create and I can't figure out how to pass params users to get method. here is create method for project controller

  def create
      @project = Project.new(project_params)
      @project.creator = current_user
      byebug
      if params[:project][:users].any?
        byebug
        params[:project][:users].reject!(&:empty?)
        @project.enrolled_user = User.find( params[:project][:users])
      end
    byebug
      authorize @project
      respond_to do |format|
        if @project.save
          format.html { redirect_to @project, notice: 'Project was successfully 
           created.'}
          format.json { render :show, status: :created, location: @project}
        else
          format.html { render :new}
          format.json { render json: @project.errors, status: :unprocessable_entity}
        end
      end
    end

project_spec.rb

  context "post create" do
  it "creates a new project" do
    get :new
    byebug
   
    post :create,params: { user: user.id }
    byebug
    

    expect(project1.creator).to eq(user)
    expect(enrolled_user.user_id).to eq(user1.id)
    expect(response).to be_successful
  end
end

terminal

 1) ProjectsController post create creates a new project
 Failure/Error: if params[:project][:users].any?
 
 NoMethodError:
   undefined method `[]' for nil:NilClass
 # ./app/controllers/projects_controller.rb:38:in `create'
 # ./spec/requests/project_spec.rb:49:in `block (3 levels) in <main>'