test: add text attribute testing function

This will be used for testing attributed strings

damusTests/Util/AttrStringTestExtensions.swift

@@ -0,0 +1,27 @@
+//
+//  AttrStringTestExtensions.swift
+//  damusTests
+//
+//  Created by William Casarin on 2023-07-17.
+//
+
+import Foundation
+import XCTest
+
+extension NSAttributedString {
+    func testAttributes(conditions: [([Key: Any]) -> Void]) throws {
+        var count = 0
+
+        self.enumerateAttributes(in: .init(0..<self.length)) { attrs, range, stop in
+            if count > conditions.count {
+                XCTAssert(false, "too many attributes \(count) attrs > \(conditions.count) conditions")
+            }
+
+            conditions[count](attrs)
+
+            count += 1
+        }
+
+        XCTAssertEqual(count, conditions.count)
+    }
+}