Fix tests on older Xcodes

Tests/ColorComponentsTests/XCHelpers/AssertViewBody.swift

@@ -2,19 +2,20 @@
 import XCTest
 import SwiftUI
 
+@available(iOS 13.0, macOS 10.15, tvOS 13.0, watchOS 6.0, *)
 @MainActor
 func XCTAssertBody<V: View, Expected: View & Equatable>(
     of view: V,
     equals body: @autoclosure () throws -> Expected,
     _ message: @autoclosure () -> String = "",
     file: StaticString = #filePath, line: UInt = #line)
 {
+    let viewBody = view.body
     // Xcode as of version 16 erases all `some` return types to their `@_typeErasure` type (if any).
     // There is a build setting for projects (SWIFT_ENABLE_OPAQUE_TYPE_ERASURE=NO), but that's not possible for SPM packages.
     // However, we can "unpack" the any view for these builds. Worst case scenario: We don't check the view body.
     // Kudos to Joe Groff for digging up the build setting: https://f.duriansoftware.com/@joe/113170928606701687
 #if Xcode && swift(>=6.0)
-    let viewBody = view.body
     XCTAssert(type(of: viewBody) == Expected.self || type(of: viewBody) == AnyView.self, "\(type(of: viewBody)) != \(Expected.self) || \(AnyView.self): \(message())",
               file: file, line: line)
     if let expectedTypeBody = viewBody as? Expected {
@@ -24,8 +25,8 @@ func XCTAssertBody<V: View, Expected: View & Equatable>(
         XCTAssertEqual(actualView as? Expected, try body(), message(), file: file, line: line)
     }
 #else
-    XCTAssert(type(of: view.body) == Expected.self, "\(type(of: view.body)) != \(Expected.self): \(message())", file: file, line: line)
-    XCTAssertEqual(view.body as? Expected, try body(), message(), file: file, line: line)
+    XCTAssert(type(of: viewBody) == Expected.self, "\(type(of: viewBody)) != \(Expected.self): \(message())", file: file, line: line)
+    XCTAssertEqual(viewBody as? Expected, try body(), message(), file: file, line: line)
 #endif
 }
 #endif