package main

import "testing"

// 测试替身：只提供接口需要的方法，不依赖真实 Student 或 Teacher。
type fakeIntroducer struct {
	text string
}

func (fake fakeIntroducer) Introduce() string {
	return fake.text
}

func TestIntroduction(t *testing.T) {
	fake := fakeIntroducer{text: "固定测试内容"}
	got := introduction(fake)
	if got != fake.text {
		t.Fatalf("实际=%q，期望=%q", got, fake.text)
	}
}

func TestImplementations(t *testing.T) {
	tests := []struct {
		name   string
		person Introducer
		want   string
	}{
		{name: "student", person: Student{Name: "小朱"}, want: "我是学生：小朱"},
		{name: "teacher", person: Teacher{Name: "王老师", Subject: "Go"}, want: "我是老师：王老师，教授Go"},
		{name: "assistant", person: &Assistant{Name: "小陈"}, want: "我是助教：小陈"},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			if got := introduction(tt.person); got != tt.want {
				t.Errorf("实际=%q，期望=%q", got, tt.want)
			}
		})
	}
}

func TestInterfaceNil(t *testing.T) {
	var empty Introducer
	if empty != nil {
		t.Fatal("未赋值接口应为 nil")
	}
	var assistant *Assistant
	var person Introducer = assistant
	if person == nil {
		t.Fatal("包含具体类型的 nil 指针接口不应等于 nil")
	}
	if got := person.Introduce(); got != "助教信息为空" {
		t.Errorf("nil 助教的介绍不符合预期：%q", got)
	}
}