 private func rebase(_ arcs: String..., at base: AbsolutePath) -> String {
   base.appending(components: arcs).pathString.nativePathString()
 }
+
+private var testInputsPath: AbsolutePath = {
+  var root: AbsolutePath = AbsolutePath(#file)
+  while root.basename != "Tests" {
+    root = root.parentDirectory
+  }
+  return root.parentDirectory.appending(component: "TestInputs")
+}()
 
 final class SwiftDriverTests: XCTestCase {
 

  }

  func testPrebuiltModuleCacheFlags() throws {
    let packageRootPath = URL(fileURLWithPath: #file).pathComponents
      .prefix(while: { $0 != "Tests" }).joined(separator: "/").dropFirst()
    let testInputsPath = packageRootPath + "/TestInputs"
    let mockSDKPath : String = testInputsPath + "/mock-sdk.sdk"

    do {
      var driver = try Driver(args: ["swiftc", "-target", "x86_64-apple-ios13.1-macabi", "foo.swift", "-sdk", mockSDKPath])


  func testDarwinSDKTooOld() throws {
    func getSDKPath(sdkDirName: String) -> AbsolutePath {
      return testInputsPath.appending(component: "SDKChecks").appending(component: sdkDirName)
    }

    // Ensure an error is emitted for an unsupported SDK
    func checkSDKUnsupported(sdkDirName: String)
    throws {
