Add tests
Add tests

Test the default behavior when building in a folder with various numbers of solution files, solution filter files, and projects files.

AndyGerlicher/msbuild,mono/msbuild,cdmihai/msbuild,sean-gilliam/msbuild,cdmihai/msbuild,rainersigwald/msbuild,AndyGerlicher/msbuild,rainersigwald/msbuild,mono/msbuild,cdmihai/msbuild,mono/msbuild,mono/msbuild,AndyGerlicher/msbuild,AndyGerlicher/msbuild,sean-gilliam/msbuild,sean-gilliam/msbuild,cdmihai/msbuild,rainersigwald/msbuild,rainersigwald/msbuild,sean-gilliam/msbuild