我们为什么需要模拟（Mocks）？

1sealed trait Course:
2  val title: String
3  val author: Author
4  val lessons: Set[Lesson]
5  val tags: Set[String]
6
7  val price: BigDecimal
8
9  val published: Boolean
10
11  require(lessons.nonEmpty || !published, "课程只有在至少包含一个课时的情况下才能发布")
12
13  def copy(
14           title: String = title,
15           author: Author = author,
16           lessons: Set[Lesson] = lessons,
17           tags: Set[String] = tags,
18           published: Boolean = published
19         ): Course
20
21case class FreeCourse(
22                       override val title: String,
23                       override val author: Author,
24                       override val lessons: Set[Lesson],
25                       override val tags: Set[String],
26                       override val published: Boolean
27                     ) extends Course:
28  override val price: BigDecimal = ??? // 如前所述
29
30case class PaidCourse(
31                       override val title: String,
32                       override val author: Author,
33                       override val lessons: Set[Lesson],
34                       override val tags: Set[String],
35                       override val published: Boolean
36                     ) extends Course:
37  override val price: BigDecimal = ??? // 如前所述
38
39class Educative(val courses: Seq[Course]):
40  // Educative 的其余部分如前所述
41
42  def publishCourse(title: String): Educative = Educative(courses map { c =>
43    if c.title == title && c.lessons.nonEmpty && !c.published then c.copy(published = true)
44    else c
45  })

1  class CourseDouble(
2      t: String,
3      ls: Set[Lesson],
4      pub: Boolean
5    ) extends Course:
6    var titleInvoked = false
7    var lessonsInvoked = false
8    var publishedInvoked = false
9    var copyInvoked = false
10
11    override def title: String =
12      titleInvoked = true
13      t
14
15    override def lessons: Set[Lesson] =
16      lessonsInvoked = true
17      ls
18
19    override def published: Boolean =
20      publishedInvoked = true
21      pub
22
23    def copy(
24              title: String,
25              author: Author,
26              lessons: Set[Lesson],
27              tags: Set[String],
28              published: Boolean
29            ): CourseDouble =
30      val newCourse = CourseDouble(t, ls, published)
31
32      newCourse.titleInvoked = titleInvoked
33      newCourse.lessonsInvoked = lessonsInvoked
34      newCourse.publishedInvoked = publishedInvoked
35      newCourse.copyInvoked = true
36
37      newCourse
38
39    override def author: Author = Author("未", "使用")
40    override def tags: Set[String] = Set.empty
41    override def price: BigDecimal = 0

1trait Course:
2  def title: String
3  val author: Author
4  def lessons: Set[Lesson]
5  val tags: Set[String]
6
7  val price: BigDecimal
8
9  def published: Boolean
10
11  // Course 的其余部分如前所述