Testing some heavy memory consumption code

I have some cache-class witch aggregates some heavy objects for optimization in production. I need to test code witch using cache but logic not related to cache. How can I avoid using cache? And run getting objects on-the-fly, not using cache. I thought about reflection, but it force me to suffer. Is it design problem or maybe I try to do something wrong?

case class SomeObject()

class FooService(private val cacheMap: collection.mutable.Map[String, SomeObject]) {

  /// some cache logic with put objects to cache

  def put(key: String, value: SomeObject): collection.mutable.Map[String, SomeObject] = cacheMap += key -> value

  def get(key: String): Option[SomeObject] = cacheMap.get(key)

  private def loadFromFile(file: String): SomeObject = ???

  def loadObject(key: String): SomeObject = {
      // ... some logic from loading 
    cacheMap.getOrElseUpdate(key, loadFromFile("some_path"))
  }
}


class Bar {

  val fooCache = new FooService(collection.mutable.Map.empty[String, SomeObject])

  def methodForTest(args: List[String]): SomeObject = {
    // do some logic ...
    val someObject = fooCache.loadObject("someKey") // here I can't create filePath for loading directly from file
    // fooCache updates, but I don't want it
    someObject
  }
}