Add FOUNDATION_EXIT_TESTS conditional

Author: jmschonfeld

Package.swift

@@ -75,6 +75,10 @@ let wasiLibcCSettings: [CSetting] = [
     .define("_WASI_EMULATED_MMAN", .when(platforms: [.wasi])),
 ]
 
+let testOnlySwiftSettings: [SwiftSetting] {
+    .define("FOUNDATION_EXIT_TESTS", .when(platforms: [.macOS, .linux, .openBSD])) // The latest Windows toolchain does not yet have exit tests in swift-testing
+}
+
 let package = Package(
     name: "swift-foundation",
     platforms: [.macOS("15"), .iOS("18"), .tvOS("18"), .watchOS("11")],
@@ -171,7 +175,7 @@ let package = Package(
                 "LifetimeDependenceMutableAccessors",
                 .when(platforms: [.macOS, .iOS, .watchOS, .tvOS, .linux])
               ),
-            ] + availabilityMacros + featureSettings
+            ] + availabilityMacros + featureSettings + testOnlySwiftSettings
         ),
 
         // FoundationInternationalization
@@ -204,7 +208,7 @@ let package = Package(
                 "TestSupport",
                 "FoundationInternationalization",
             ],
-            swiftSettings: availabilityMacros + featureSettings
+            swiftSettings: availabilityMacros + featureSettings + testOnlySwiftSettings
         ),
 
         // FoundationMacros
@@ -236,7 +240,7 @@ package.targets.append(contentsOf: [
             "FoundationMacros",
             "TestSupport"
         ],
-        swiftSettings: availabilityMacros + featureSettings
+        swiftSettings: availabilityMacros + featureSettings + testOnlySwiftSettings
     )
 ])
 #endif

Tests/FoundationEssentialsTests/AttributedString/AttributedStringIndexTrackingTests.swift

@@ -173,6 +173,7 @@ private struct AttributedStringIndexTrackingTests {
         #expect(String(text[helloRange].characters) == "He")
     }
 
+    #if FOUNDATION_EXIT_TESTS
     @Test
     func trackingLostPreconditions() async {
         await #expect(processExitsWith: .failure) {
@@ -207,6 +208,7 @@ private struct AttributedStringIndexTrackingTests {
             }
         }
     }
+    #endif
 
     @Test
     func trackingLost() throws {
@@ -261,6 +263,7 @@ private struct AttributedStringIndexTrackingTests {
         #expect(AttributedString(text[updatedRanges[1]]) == original[worldRange].settingAttributes(AttributeContainer.testInt(2)))
     }
 
+    #if FOUNDATION_EXIT_TESTS
     @Test
     func invalidInputRanges() async {
         await #expect(processExitsWith: .failure) {
@@ -288,4 +291,5 @@ private struct AttributedStringIndexTrackingTests {
             }
         }
     }
+    #endif
 }