Fix ups based on review.

* Add test conditional Trait for detecting thread safe
  working directories.  Issue present on Amazon linux
* Get rid of 'nil' parameter to @test macro.
* Remove all XCTest calls from Helpers.swift
* Add known issues to the binaryTargets() test, which
  was previously unconditionally skipped.
* Remove unused XCTest imports

Author: kcieplak

IntegrationTests/Sources/IntegrationTestSupport/Helpers.swift

@@ -9,10 +9,9 @@
  */
 
 import Foundation
+import Testing
 import TSCBasic
 import TSCTestSupport
-import XCTest
-
 import enum TSCUtility.Git
 
 public let sdkRoot: AbsolutePath? = {
@@ -136,10 +135,12 @@ public func sh(
     let stderr = try result.utf8stderrOutput()
 
     if result.exitStatus != .terminated(code: 0) {
-        XCTFail(
-            "Command failed with exit code: \(result.exitStatus) - \(result.integrationTests_debugDescription)",
-            file: file, line: line
-        )
+        Issue
+            .record(
+                Comment(
+                    "Command failed with exit code: \(result.exitStatus) - \(result.integrationTests_debugDescription)"
+                )
+            )
     }
 
     return (stdout, stderr)
@@ -157,10 +158,12 @@ public func shFails(
     let stderr = try result.utf8stderrOutput()
 
     if result.exitStatus == .terminated(code: 0) {
-        XCTFail(
-            "Command unexpectedly succeeded with exit code: \(result.exitStatus) - \(result.integrationTests_debugDescription)",
-            file: file, line: line
-        )
+        Issue
+            .record(
+                Comment(
+                    "Command unexpectedly succeeded with exit code: \(result.exitStatus) - \(result.integrationTests_debugDescription)"
+                )
+            )
     }
 
     return (stdout, stderr)
@@ -222,7 +225,7 @@ public func fixture(
 
             // Check that the fixture is really there.
             guard localFileSystem.isDirectory(fixtureDir) else {
-                XCTFail("No such fixture: \(fixtureDir)", file: file, line: line)
+                Issue.record(Comment("No such fixture: \(fixtureDir)"))
                 return
             }
 
@@ -257,7 +260,7 @@ public func fixture(
             }
         }
     } catch {
-        XCTFail("\(error)", file: file, line: line)
+        Issue.record(error)
     }
 }
 
@@ -302,7 +305,7 @@ public func initGitRepo(
             try systemQuietly([Git.tool, "-C", dir.pathString, "tag", tag])
         }
     } catch {
-        XCTFail("\(error)", file: file, line: line)
+        Issue.record(error)
     }
 }
 

IntegrationTests/Sources/IntegrationTestSupport/SkippedTestSupport.swift

@@ -9,44 +9,55 @@
  See http://swift.org/CONTRIBUTORS.txt for Swift project authors
  */
 
+import class Foundation.FileManager
 import class Foundation.ProcessInfo
 import Testing
 
 extension Trait where Self == Testing.ConditionTrait {
-    // Skip test if the host operating system does not match the running OS.
+    /// Skip test if the host operating system does not match the running OS.
     public static func requireHostOS(_ os: OperatingSystem, when condition: Bool = true) -> Self {
         enabled("This test requires a \(os) host OS.") {
             ProcessInfo.hostOperatingSystem == os && condition
         }
     }
 
-    // Skip test if the host operating system matches the running OS.
+    /// Skip test if the host operating system matches the running OS.
     public static func skipHostOS(_ os: OperatingSystem, _ comment: Comment? = nil) -> Self {
         disabled(comment ?? "This test cannot run on a \(os) host OS.") {
             ProcessInfo.hostOperatingSystem == os
         }
     }
 
-    // Skip test unconditionally
+    /// Skip test unconditionally
     public static func skip(_ comment: Comment? = nil) -> Self {
         disabled(comment ?? "Unconditional skip, a comment should be added for the reason") { true }
     }
 
-    // Skip test if the environment is self hosted.
+    /// Skip test if the environment is self hosted.
     public static func skipSwiftCISelfHosted(_ comment: Comment? = nil) -> Self {
         disabled(comment ?? "SwiftCI is self hosted") {
             ProcessInfo.processInfo.environment["SWIFTCI_IS_SELF_HOSTED"] != nil
         }
     }
 
-    // Skip test if built by XCode.
+    /// Skip test if built by XCode.
     public static func skipIfXcodeBuilt() -> Self {
-        disabled {
+        disabled("Tests built by Xcode") {
             #if Xcode
             true
             #else
             false
             #endif
         }
     }
+
+    /// Constructs a condition trait that causes a test to be disabled if the Foundation process spawning implementation
+    /// is not using `posix_spawn_file_actions_addchdir`.
+    public static var requireThreadSafeWorkingDirectory: Self {
+        disabled("Thread-safe process working directory support is unavailable.") {
+            // Amazon Linux 2 has glibc 2.26, and glibc 2.29 is needed for posix_spawn_file_actions_addchdir_np support
+            FileManager.default.contents(atPath: "/etc/system-release")
+                .map { String(decoding: $0, as: UTF8.self) == "Amazon Linux release 2 (Karoo)\n" } ?? false
+        }
+    }
 }

IntegrationTests/Sources/IntegrationTestSupport/StringChecker.swift

@@ -10,8 +10,6 @@
 
 import Foundation
 import TSCTestSupport
-import XCTest
-
 public class StringChecker {
     private let string: String
     private let lines: [Substring]