Scala 在所有测试运行之前，仅初始化值一次

我只想在所有测试运行之前初始化值一次

现在，如果可以只运行一次，那么值

insertDbScheme

createscheme将出现在每个测试中。从sbt任务插入方案不合适

我有两个测试

测试1：

class Test1 extends Specification with InsertDbScheme {

  "test" in {
    insertDbScheme
    // some code
    ok
  }
}

测试2：

class Test2 extends Specification with InsertDbScheme {

  "test" in {
    insertDbScheme
    // some code
    ok
  }
}

以及将scheme插入数据库的基本特征

trait InsertDbScheme {

  lazy val insertDbScheme = {
    println("insert scheme to database")
  }
}

运行测试的结果

insert scheme to database
insert scheme to database
[info] Test1
[info] 
[info] + test
[info] 
[info] 
[info] Total for specification Test1
[info] Finished in 152 ms
[info] 1 example, 0 failure, 0 error
[info] 
[info] Test2
[info] 
[info] + test
[info] 
[info] 
[info] Total for specification Test2
[info] Finished in 152 ms
[info] 1 example, 0 failure, 0 error
[info] 
[info] ScalaCheck
[info] Passed: Total 0, Failed 0, Errors 0, Passed 0
[info] Passed: Total 2, Failed 0, Errors 0, Passed 2
[success] Total time: 12 s, completed May 18, 2017 6:35:21 PM

---

您可以使用

对象

来确保它的

惰性val

只实例化一次：

trait InsertDbScheme {
  import InsertDbScheme._
  lazy val insertDbScheme = insertDbSchemeOnce
}

object InsertDbScheme { 
  lazy val insertDbSchemeOnce = {
    println("insert scheme to database")
  }
}

---

最简单的方法是在

InsertDbScheme

对象中使用变量：

trait InsertDbScheme {

  def insertDbScheme = synchronized {
    if (!InsertDbScheme.done) {
      println("insert scheme to database")
      InsertDbScheme.done = true
    }        
  }
}

object InsertDbScheme {
  var done = false
}