Add document about RKP VM marker testing in VM attestation

Bug: 365692904
Test: N/A
Change-Id: I9c480da2f5962b191136880e24e66439713f4bea
diff --git a/docs/vm_remote_attestation.md b/docs/vm_remote_attestation.md
index ee20591..2ee0fae 100644
--- a/docs/vm_remote_attestation.md
+++ b/docs/vm_remote_attestation.md
@@ -126,7 +126,7 @@
 
 To support VM remote attestation, vendors must include an RKP VM marker in their
 DICE certificates. This marker should be present from the early boot stage
-within the TEE and continue through to the last DICE certificate before
+within the TEE and continue through to the leaf DICE certificate before
 [pvmfw][pvmfw] takes over.
 
 ![RKP VM DICE chain][rkpvm-dice-chain]
@@ -140,6 +140,20 @@
 server because it will lack the RKP VM marker that pvmfw would have added in a
 genuine RKP VM boot process.
 
+### Testing
+
+To ensure the correct implementation and usage of RKP VM markers, we've
+incorporated comprehensive checks into various xTS tests (e.g.,
+`VtsHalRemotelyProvisionedComponentTargetTest`).
+
+These tests validate the following conditions:
+
+- The RKP VM DICE chain must have a continuous presence of at least two RKP VM
+  markers, extending to the leaf DICE certificate.
+- Non-RKP VM DICE chains must not have a continuous presence of two or more RKP
+  VM markers, preventing non-RKP VM chains from being incorrectly identified as
+  RKP VM chains.
+
 [pvmfw]: ../guest/pvmfw/README.md
 [rkpvm-dice-chain]: img/rkpvm-dice-chain.png