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trait PrivateMethodTester extends AnyRef

Trait that facilitates the testing of private methods.

To test a private method, mix in trait PrivateMethodTester and create a PrivateMethod object, like this:

val decorateToStringValue = PrivateMethod[String]('decorateToStringValue)

The type parameter on PrivateMethod, in this case String, is the result type of the private method you wish to invoke. The symbol passed to the PrivateMethod.apply factory method, in this case 'decorateToStringValue, is the name of the private method to invoke. To test the private method, use the invokePrivate operator, like this:

targetObject invokePrivate decorateToStringValue(1)

Here, targetObject is a variable or singleton object name referring to the object whose private method you want to test. You pass the arguments to the private method in the parentheses after the PrivateMethod object. The result type of an invokePrivate operation will be the type parameter of the PrivateMethod object, thus you need not cast the result to use it. In other words, after creating a PrivateMethod object, the syntax to invoke the private method looks like a regular method invocation, but with the dot (.) replaced by invokePrivate. The private method is invoked dynamically via reflection, so if you have a typo in the method name symbol, specify the wrong result type, or pass invalid parameters, the invokePrivate operation will compile, but throw an exception at runtime.

One limitation to be aware of is that you can't use PrivateMethodTester to test a private method declared in a trait, because the class the trait gets mixed into will not declare that private method. Only the class generated to hold method implementations for the trait will have that private method. If you want to test a private method declared in a trait, and that method does not use any state of that trait, you can move the private method to a companion object for the trait and test it using PrivateMethodTester that way. If the private trait method you want to test uses the trait's state, your best options are to test it indirectly via a non-private trait method that calls the private method, or make the private method package access and test it directly via regular static method invocations.

Also, if you want to use PrivateMethodTester to invoke a parameterless private method, you'll need to use empty parens. Instead of:

targetObject invokePrivate privateParameterlessMethod

You'll need to write:

targetObject invokePrivate privateParameterlessMethod()

Source
PrivateMethodTester.scala
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PrivateMethodTester
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Type Members

  1. final class Invocation[T] extends AnyRef

    Class whose instances represent an invocation of a private method.

    Class whose instances represent an invocation of a private method. Instances of this class contain the name of the private method (methodName) and the arguments to pass to it during the invocation (args). The type parameter, T, is the return type of the private method.

    Exceptions thrown

    NullArgumentException if methodName is null

  2. final class Invoker extends AnyRef

    Class used via an implicit conversion to enable private methods to be tested.

  3. final class PrivateMethod[T] extends AnyRef

    Represent a private method, whose apply method returns an Invocation object that records the name of the private method to invoke, and any arguments to pass to it when invoked.

    Represent a private method, whose apply method returns an Invocation object that records the name of the private method to invoke, and any arguments to pass to it when invoked. The type parameter, T, is the return type of the private method.

    Exceptions thrown

    NullArgumentException if methodName is null

Value Members

  1. final def !=(arg0: Any): Boolean
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  2. final def ##(): Int
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  3. final def ==(arg0: Any): Boolean
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  4. implicit def anyRefToInvoker(target: AnyRef): Invoker

    Implicit conversion from AnyRef to Invoker, used to enable assertions testing of private methods.

    Implicit conversion from AnyRef to Invoker, used to enable assertions testing of private methods.

    target

    the target object on which to invoke a private method.

    Exceptions thrown

    NullArgumentException if target is null.

  5. final def asInstanceOf[T0]: T0
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  6. def clone(): AnyRef
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  8. def equals(arg0: Any): Boolean
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  9. def finalize(): Unit
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  10. final def getClass(): Class[_]
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  11. def hashCode(): Int
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  14. final def notify(): Unit
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  16. final def synchronized[T0](arg0: ⇒ T0): T0
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  17. def toString(): String
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  18. final def wait(): Unit
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  19. final def wait(arg0: Long, arg1: Int): Unit
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  20. final def wait(arg0: Long): Unit
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  21. object PrivateMethod

    Contains a factory method for instantiating PrivateMethod objects.

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