Groovy mocking File Designer, check the entry in newly created files

Question

I am trying to make fun of a new file generated in a loop. A simplified example:

class FileClass {

  def basePath
  def listObjects = []

  def createFilePerObject() {
    listObjects.each {currentObject ->
      File currentFile = new File("${basePath.toString()}/${currentObject.objectName}")

      currentFile.write currentObject.objectContent   //Verify this behaviour!!
    }
  }

}

class SimpleObject {
  String objectName
  String objectContent
}

And, the test:

class FileClassTest extends Specification {

  FileClass fileClass

  def "test simple object"() {

    def listObjects = []

    SimpleObject object1 = new SimpleObject(objectName: "First object", objectContent: "First object content")
    SimpleObject object2 = new SimpleObject(objectName: "Second object", objectContent: "Second object content")
    SimpleObject object3 = new SimpleObject(objectName: "Third object", objectContent: "Third object content")
    SimpleObject object4 = new SimpleObject(objectName: "Fourth object", objectContent: "Fourth object content")

    listObjects << object1
    listObjects << object2
    listObjects << object3
    listObjects << object4

    fileClass = new FileClass(listObjects: listObjects, basePath: ".")

    def dummyFile = new MockFor(File)
    def mockFile = new MockFor(File, true)  //Intercept constructor call

    mockFile.demand.with {
      File() {dummyFile}
    }

    when:
    mockFile.use {
      fileClass.createFilePerObject()
    }

    then:
    1 * mockFile.write(_)
  }

}

So, as you can see, I'm trying to verify that the new files have something written in them.

And I get the following error:

MockFor with constructor interception enabled is only allowed for Groovy objects but found: java.io.File

So, the file, as I understand it, is expanded in groovy GDK (Groovy JDK), and it has additional (and very useful) methods. But groovy is trying to mock java.io.File.

And, following the logic of the error, I decided to actually create the File constructor as follows:

class FileClassTest extends Specification {

  FileClass fileClass

  def "test simple object"() {

    def listObjects = []

    SimpleObject object1 = new SimpleObject(objectName: "First object", objectContent: "First object content")
    SimpleObject object2 = new SimpleObject(objectName: "Second object", objectContent: "Second object content")
    SimpleObject object3 = new SimpleObject(objectName: "Third object", objectContent: "Third object content")
    SimpleObject object4 = new SimpleObject(objectName: "Fourth object", objectContent: "Fourth object content")

    listObjects << object1
    listObjects << object2
    listObjects << object3
    listObjects << object4

    fileClass = new FileClass(basePath: ".", listObjects: listObjects)

    def mockFile = new MockFor(File)

    File.metaClass.constructor << {String filePath -> mockFile } //Return the mocked file, so it can be verified

    when:
    mockFile.use {
      fileClass.createFilePerObject()
    }

    then:
    1 * mockFile.write(_)
  }

}

And I got a warning that the constructor already exists (I think I can not completely remove it):

groovy.lang.GroovyRuntimeException: Cannot add new constructor for arguments [[class java.lang.String]]. It already exists!

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Answer 1

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