test(identity): cover seed allocation and invalid reads

Author: Kyle-Ye

Tests/OpenSwiftUITests/View/IdentityLinkTests.swift

@@ -0,0 +1,52 @@
+//
+//  IdentityLinkTests.swift
+//  OpenSwiftUITests
+
+import OpenAttributeGraphShims
+#if OPENSWIFTUI_ENABLE_PRIVATE_IMPORTS
+@_private(sourceFile: "IdentityLink.swift")
+#endif
+@testable import OpenSwiftUI
+@_spi(ForOpenSwiftUIOnly) import OpenSwiftUICore
+import Testing
+
+@MainActor
+@Suite
+struct IdentityLinkTests {
+    @Test
+    func seed() {
+        let identities = (0..<64).map { _ in ViewIdentity() }
+        #expect(Set(identities).count == 64)
+        #expect(!identities.contains(.invalid))
+    }
+
+    #if OPENSWIFTUI_ENABLE_PRIVATE_IMPORTS
+    @Test
+    func overflow() {
+        ViewIdentity.nextSeed = UInt32.max
+        let id1 = ViewIdentity()
+        #expect(id1.seed == UInt32.max)
+        let id2 = ViewIdentity()
+        #expect(id2 != .invalid)
+        #expect(id2.seed == 1)
+    }
+    #endif
+
+    #if !os(iOS) && !os(visionOS)
+    @Test
+    func readingBeforeInstallationFails() async throws {
+        let result = try await #require(
+            processExitsWith: .failure,
+            observing: [\.standardErrorContent]
+        ) {
+            _ = IdentityLink().wrappedValue
+        }
+        #if DEBUG
+        let diagnostic = String(decoding: result.standardErrorContent, as: UTF8.self)
+        #expect(diagnostic.contains("Reading IdentityLink outside View.body"))
+        #else
+        _ = result
+        #endif
+    }
+    #endif
+}