     }
 
     func testSwiftExecWithCDep() {
-#if false
+#if os(macOS)
         fixture(name: "ClangModules/SwiftCMixed") { prefix in
             // This will also test Modulemap generation for xcodeproj.
             XCTAssertXcodeprojGen(prefix)

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