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DeveloperDocumentation.md

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Developer Documentation

This document is targeted for developers who would like to undertand and potentially contribute to the SimpleStubs source code.

Build & Code Generation

SimpleStubs used Roslyn to generate stubs. The code is generated during the build (right before the build actually).

When SimpleStubs NuGet package is installed to a given project, the Etg.SimpleStubs.targets file is installed and imported in the ProjectName.nuget.targets file (which gets added to the target project). The Etg.SimpleStubs.targets file contains a BeforeBuild task that executes the GenerateStubsTask visual studio Task and writes the output to the "$(ProjectDir)Properties\SimpleStubs.generated.cs" file. This Task calls the SimpleStubsGenerator which walks through all dependent projects and generate corresponding stubs.

Method and Property Stubbers

If you follow the source code starting at SimpleStubsGenerator, you'll notice that the InterfaceStubber class is used to generate a stub for a given interface. The constructor of InterfaceStubber is as follows:

        public InterfaceStubber(IEnumerable<IMethodStubber> methodStubbers, IEnumerable<IPropertyStubber> propertyStubbers)
        {
            _propertyStubbers = propertyStubbers;
            _methodStubbers = new List<IMethodStubber>(methodStubbers);
        }

When an interface is stubbed, the InterfaceStubber walks through all the method/property stubbers and execute them all on each method/property in the interface. This means that you can easily add your own implementation of IMethodStubber/IPropertyStubber and it will be invoked as part of the build. To inject your own IMethodStubber/IPropertyStubber, simply update the DIModule code and add an additional entry where the constructor of InterfaceStubber is being invoked. You can also modify existing implementations of IMethodStubber/IPropertyStubber to fix bugs or add behaviour.

Testing

The test folder contains a class library project and a corresponding test project. The test project is setup in a way that it will invoke SimpleStubs with the current version of the Etg.SimpleStubs.CodeGen.dll that is available in the build directory (see Etg.SimpleStubs.targets). This will allow developers to modify the SimpleStubs code and run the unit tests without having to re-generate the NuGet every time. One issue I noticed with this approach is that Visual Studio ends up locking the Etg.SimpleStubs.CodeGen.dll and it won't be updated during the build. When that happens, the only solution I am currently aware of is to restart visual studio.

If you want to avoid dealing with dlls being locked or to debug SimpleStubs code generation, there is a test that has been added specifically added for these purposes in the test class called TestGenerateStubs. Enable this test when needed (by removing the [Ignore]) and it'll generate the stubs and write them to the same SimpleStubs.generated.cs file.