         var fs = InMemoryFileSystem()
         try fs.createEmptyFiles("/Sources/main.swift",
                                 "/Sources/main.c")
-        PackageBuilderTester(.root, in: fs) { result in
+        PackageBuilderTester("MixedSources", in: fs) { result in
             result.checkError("the module at /Sources contains mixed language source files fix: use only a single language within a module")
         }
     }

    }
}

/// Loads a package using PackageBuilder at the given path. If package description is provided it is used,
/// otherwise a default package with name of directory is passed to manifest.
///
/// - Parameters:
///     - path: Directory where the package is located.
///     - in: FileSystem in which the package should be loaded from.
///     - package: PackageDescription instance to use for loading this package.
///
/// - Throws: ModuleError, ProductError
private func loadPackage(_ path: AbsolutePath, in fs: FileSystem, package: PackageDescription.Package? = nil) throws -> PackageModel.Package {
    let pkg: PackageDescription.Package
    if let package = package {
        pkg = package
    } else {
        pkg = Package(name: path.basename)
    }
    let manifest = Manifest(path: path.appending(component: Manifest.filename), url: "", package: pkg, products: [], version: nil)
    let builder = PackageBuilder(manifest: manifest, path: path, fileSystem: fs)
    return try builder.construct(includingTestModules: true)
}

    var ignoreOtherModules: Bool = false

    @discardableResult
   convenience init(_ name: String, path: AbsolutePath = .root, in fs: FileSystem, file: StaticString = #file, line: UInt = #line, _ body: @noescape (PackageBuilderTester) -> Void) {
       let package = Package(name: name)
       self.init(package, path: path, in: fs, file: file, line: line, body)
    }

    @discardableResult
    init(_ package: PackageDescription.Package, path: AbsolutePath = .root, in fs: FileSystem, file: StaticString = #file, line: UInt = #line, _ body: @noescape (PackageBuilderTester) -> Void) {
        do {
            let loadedPackage = try loadPackage(package, path: path, in: fs)
            result = .package(loadedPackage)
            uncheckedModules = Set(loadedPackage.allModules)
        } catch {
