如何在ScalaTest中使用ScriptEngine

Question

以下测试应该通过，但事实并非如此

class EngineTest extends FunSuite {

  test("engine should not be null") {
    val manager: ScriptEngineManager = new ScriptEngineManager
    val engine: ScriptEngine = manager.getEngineByName("nashorn")
    assert(engine != null)
  }
}

manager.getEngineFactories()似乎是空的。为什么？如何初始化上下文？

Answer 1

你使用的是什么版本？这是s13。

> console
[info] Starting scala interpreter...
[info] 
Welcome to Scala version 2.11.0 (OpenJDK 64-Bit Server VM, Java 1.7.0_25).
Type in expressions to have them evaluated.
Type :help for more information.

scala> import javax.script._
import javax.script._

scala> new ScriptEngineManager().getEngineByName("scala")
res0: javax.script.ScriptEngine = scala.tools.nsc.interpreter.IMain@7078c799

scala> new ScriptEngineManager().getEngineByName("rhino")
res1: javax.script.ScriptEngine = com.sun.script.javascript.RhinoScriptEngine@5c854934

scala> new ScriptEngineManager().getEngineFactories
res2: java.util.List[javax.script.ScriptEngineFactory] = [com.sun.script.javascript.RhinoScriptEngineFactory@454ee4c0, scala.tools.nsc.interpreter.IMain$Factory@354e3bce]

等等，你问过测试环境 -

好吧，在我对解码更多sbt失去兴趣之前，添加到libraryDependencies：

"org.scala-lang" % "scala-compiler" % scalaVersion.value % "test",

能够找到Scala脚本引擎：

  @Test def engines: Unit = {
    import javax.script._
    val all = new ScriptEngineManager().getEngineFactories
    Console println s"Found ${all.size}: $all"
    assert(all.size > 0)
  }

毫无疑问，有一种简单的方法可以添加运行时：test-classpath to test：full-classpath。因为它是简单的构建工具，对吧？

对于Java 8上的Nashorn，请注意位置：

> set fullClasspath in Test += Attributed.blank(file(s"${util.Properties.javaHome}/lib/ext/nashorn.jar"))
[info] Defining test:fullClasspath
[info] The new value will be used by test:console, test:executeTests and 5 others.
[info]  Run `last` for details.
[info] Reapplying settings...
[info] Set current project to goofy (in build file:/home/apm/goofy/)
> test
Found 1: [jdk.nashorn.api.scripting.NashornScriptEngineFactory@7fa2239d]
[info] Passed: Total 10, Failed 0, Errors 0, Passed 10

更新：https://github.com/sbt/sbt/issues/1214

还有I guess it's still considered black art：

// Somehow required to get a js engine in tests (https://github.com/sbt/sbt/issues/1214)

fork in Test := true

Answer 2

您需要将ClassLoader显式传递给ScriptEngineManager构造函数。如果你不这样做那么它使用Thread.currentThread().getContextClassLoader()，它在SBT下运行时设置为奇怪的东西。我们只是在代码中传入null以使其工作。你也可以传递getClass.getClassLoader：

class EngineTest extends FunSuite {
  test("engine should not be null - null classloader") {
    val manager: ScriptEngineManager = new ScriptEngineManager(null)
    val engine: ScriptEngine = manager.getEngineByName("nashorn")
    assert(engine != null)
  }

  test("engine should not be null - getClass.getClassLoader classloader") {
    val manager: ScriptEngineManager = new ScriptEngineManager(getClass.getClassLoader)
    val engine: ScriptEngine = manager.getEngineByName("nashorn")
    assert(engine != null)
  }
}

这两个测试都通过了我：

[info] EngineTest:
[info] - engine should not be null - null classloader
[info] - engine should not be null - getClass.getClassLoader classloader
[info] Run completed in 186 milliseconds.
[info] Total number of tests run: 2
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 2, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.

Answer 3

我唯一需要改变的是使用：

fork in Test := true

如上所述 - 从这里：https://github.com/sbt/sbt/issues/1214