Menu
Is there any way to test a nested function (ideally with ScalaTest)?
For example, is there a way to test g() in the below code:
def f() = {
def g() = "a string!"
g() + "– says g"
}
348
A function definition inside an another function is known as Nested Function. It is not supported by C++, Java, etc. In other languages, we can call a function inside a function, but it’s not a nested function. In Scala, we can define functions inside a function and functions defined inside other functions are called nested or local functions .
In other languages, we can call a function inside a function, but it’s not a nested function. In Scala, we can define functions inside a function and functions defined inside other functions are called nested or local functions .
This concept of defining a function in the definition of another is called Nesting. Like any other code block, a nested function can also be used to define multiple code definitions inside a function. The nested function makes it easier to detect the code and increases modularity.
Here is an implementation of a factorial calculator, where we use a conventional technique of calling a second, nested method to do the work. Try the following program to implement nested functions.
g is not visible outside of f, so I daresay no, at least not without reflection.
I think testing g would break the concept of unit testing, anyway, because you should never test implementation details but only public API behaviour. Tracking an error to a mistake in g is part of the debugging process if tests for f fail.
If testing g is important for you, define g as (protected) method outside of f. That might break your design, though.
Another idea would be to put calls to assert after the call of g in the original code. This will be executed during tests and raise an exception if the property does not hold, causing the test to fail. It will be there in regular code, too, but can be removed by the compiler as assert (and companions) are elidible (see e.g. here).
109
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
