Add more complete tests for DOM attribute serialization

Author: sethfowler-datadog

packages/rum/src/domain/record/serialization/serialization.types.ts

@@ -8,3 +8,31 @@ export type ParentNodePrivacyLevel =
   | typeof NodePrivacyLevel.MASK
   | typeof NodePrivacyLevel.MASK_USER_INPUT
   | typeof NodePrivacyLevel.MASK_UNLESS_ALLOWLISTED
+
+/**
+ * Virtual attributes. These attributes appear in the serialized attribute map of
+ * elements, but they're not actually derived from the DOM; they're used to represent
+ * metadata about the element they're attached to.
+ */
+export interface VirtualAttributes {
+  /**
+   * For <style> and <link> elements, the rules in the element's stylesheet, extracted
+   * from the CSSOM.
+   */
+  _cssText?: string
+
+  /** For <audio> and <video> elements, the playback state of the element's media. */
+  rr_mediaState?: 'paused' | 'played'
+
+  /** For elements which are scroll containers, the element's X scroll position, if non-zero. */
+  rr_scrollLeft?: number
+
+  /** For elements which are scroll containers, the element's Y scroll position, if non-zero. */
+  rr_scrollTop?: number
+
+  /** For HIDDEN elements, the width of the element's bounding client rect. */
+  rr_width?: string
+
+  /** For HIDDEN elements, the height of the element's bounding client rect. */
+  rr_height?: string
+}