scala ScalaMock：如何模拟/存根方法以在每次调用时返回不同的值？
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ScalaMock: How to mock/stub a method to return different values per call?
提问by Eyal Roth
Using ScalaMock, I want to mock/stub a class method so it will return a different value per call (order of calls matters).
使用 ScalaMock，我想模拟/存根类方法，以便每次调用返回不同的值（调用顺序很重要）。
I can achieve this with mockand expects, but that will force me to verify those calls.
我可以用mock和实现这一点expects，但这将迫使我验证这些调用。
Can I do this with a stub?
我可以用 做这个stub吗？
Also, how can I say something like "first time return X, and then always return Y" (both with mockand stub)?
另外，我怎么能说“第一次返回 X，然后总是返回 Y”（包括mock和stub）？
回答by Akzok
Yes, this can be done, although the syntax is a little unintuitive:
是的，这是可以做到的，尽管语法有点不直观：
trait Foo { def getInt: Int }
val fooStub = stub[Foo]
(fooStub.getInt _).when().returns(1).noMoreThanOnce()
(fooStub.getInt _).when().returns(2).noMoreThanOnce()
(fooStub.getInt _).when().returns(3)
(fooStub.getInt _).when().returns(4)
assert(fooStub.getInt == 1)
assert(fooStub.getInt == 2)
assert(fooStub.getInt == 3)
// Note that it's fine that we don't call it a fourth time - calls are not verified.
It's important to use .noMoreThanOnce() rather than.once(), otherwise you cause the calls to be verified. There is also a .noMoreThanTwice() method, but I don't think there is a .noMoreThanNTimes() or any equivalent.
使用 .noMoreThanOnce() 而不是 .once() 很重要，否则会导致调用被验证。还有一个 .noMoreThanTwice() 方法，但我认为没有 .noMoreThanNTimes() 或任何等效方法。
Here is how to do "first time return X, and then always return Y" for mocks and stubs:
下面是如何为模拟和存根做“第一次返回 X，然后总是返回 Y”：
trait Bar { def getString: String }
val barMock = mock[Bar]
(barMock.getString _).expects().returning("X")
(barMock.getString _).expects().returning("Y").anyNumberOfTimes()
assert(barMock.getString == "X")
assert(barMock.getString == "Y")
assert(barMock.getString == "Y")
val barStub = stub[Bar]
(barStub.getString _).when().returns("x").noMoreThanOnce()
(barStub.getString _).when().returns("y")
assert(barStub.getString == "x")
assert(barStub.getString == "y")
assert(barStub.getString == "y")
回答by botchniaque
For me the best way to write a mock which does not verify calls and where returning value depends on the input is to use onCallmethod - it takes a closure of your function. By default it will serve only the first call, so make sure to add anyNumberOfTimesor some repreted(...).
对我来说，编写不验证调用并且返回值取决于输入的模拟的最佳方法是使用onCall方法 - 它需要关闭您的函数。默认情况下，它只会服务于第一次调用，因此请确保添加anyNumberOfTimes或一些repreted(...).
import org.scalamock.scalatest.MockFactory
trait Foo {
def getSomeValue(param1: Any, param2: Any): String
}
class Test extends MockFactory {
val fooMock = stub[Foo]
val it = Iterator.single("X") ++ Iterator.continually("Y")
(fooMock.getSomeValue _)
.expects(*, *)
.onCall((p1, p2) => it.next())
.anyNumberOfTimes
}
Now the first call to fooMock.someValue(...)will return Xand each consecutive Y.
现在第一次调用fooMock.someValue(...)将返回X并且每个连续的Y.
