     }
     
     func testSystemModule() {
-#if false
+#if os(macOS)
         // Because there isn't any one system target that we can depend on for testing purposes, we build our own.
         try! write(path: AbsolutePath("/tmp/fake.h")) { stream in
             stream <<< "extern const char GetFakeString(void);\n"

    }

    func testXcodeProjWithPkgConfig() {
#if false
        fixture(name: "Miscellaneous/PkgConfig") { prefix in
            let systemModule = prefix.appending(component: "SystemModule")
            // Create a shared library.

            env["TOOLCHAINS"] = "default"
        }
        let xcconfig = project.appending(component: "overrides.xcconfig")
        let swiftCompilerPath = Resources.default.swiftCompiler

        // Override path to the Swift compiler.
        let stream = BufferedOutputByteStream()
        stream <<< "SWIFT_EXEC = " <<< swiftCompilerPath.asString <<< "\n"

        // Override Swift libary path, if present.
        let swiftLibraryPath = resolveSymlinks(swiftCompilerPath).appending(components: "..", "..", "lib", "swift", "macosx")
        if localFileSystem.exists(swiftCompilerPath) {
            stream <<< "SWIFT_LIBRARY_PATH = " <<< swiftLibraryPath.asString <<< "\n"
        }
        try localFileSystem.writeFileContents(xcconfig, bytes: stream.bytes)

        try Process.checkNonZeroExit(
            args: "xcodebuild", "-project", project.asString, "-alltargets", "-xcconfig", xcconfig.asString, environment: env)
    } catch {
