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Project components

Stryker.NET uses custom classes to keep track of folders and files. These classes are based on the composite pattern.

These FolderComposite and FileLeafs have readonly variants, this is done to ensure the mutated source code and Mutants are not changed after the mutation is placed.

UML of the classes in the namespace Stryker.Core.ProjectComponents

Folder Components

Old Design

The global structure was as follows:

  • FolderComposite
  • FileLeaf

With the abstract class they both implement:

  • ProjectComponent

New Design

When implementing F# the old structure showed it's disadvantages since F# uses a different type to indicate syntax trees.

To solve this ProjectComponent was made generic ProjectComponent<T>.

However many parts of stryker use FolderComposite and FileLeaf without needing access to the syntax trees or to know what language is used. For this purpose the Interface IProjectComponent is used.

IFolderComposite and IFileLeaf are implemented for the same reason. This enables code to ask for an IFileLeaf so It can access the elements that do not depend on the language, that being all except the syntax trees.

For applications that do need access to the syntax trees ProjectComponent<T> can be used or the specific type, being:

  • CsharpFolderComposite
  • CsharpFileLeaf


  • FsharpFolderComposite
  • FsharpFileLeaf

IFileLeaf<T> is needed to have language agnostic notation for the syntax trees.

ReadOnly variants

Not al code is created equally, and not all parts of stryker need write access to the ProjectComponents. This is why a IReadOnlyProjectComponent was created.

When expanding into F# we found the implementation lacking and expanded upon it. There are ReadOnly variants of FolderComponent and FileLeaf:

  • ReadOnlyFolderComponent
  • ReadOnlyFileLeaf

The readonly variants do not need access to the syntax trees so they are language agnostic which improves the expandability of Stryker.NET

The variant of FolderComponent and FileLeaf all contain the functions ToReadOnly() and ToReadOnlyInputComponent().

ToReadOnly() returns the ReadOnly variant of said type. ToReadOnlyInputComponent() does the same, just casted to IReadOnlyProjectComponent.

ToReadOnly() takes the interfaces IParentComponent and IFileLeaf as input so the readonly variants do not need to distinguish between CsharpFileLeaf and FsharpFileLeaf for example.


FolderComponent and FileLeaf are NOT classes that exist in Stryker.NET only the language specific implementations exist!