diff --git a/codexvalidator/basics.nim b/codexvalidator/basics.nim
index 0145102..fe8adad 100644
--- a/codexvalidator/basics.nim
+++ b/codexvalidator/basics.nim
@@ -1,7 +1,7 @@
 import std/sequtils
+import pkg/stint
+import pkg/questionable
 
 export sequtils
-
-import pkg/stint
-
 export stint
+export questionable
diff --git a/codexvalidator/blocks.nim b/codexvalidator/blocks.nim
index 9ab3228..00c2aab 100644
--- a/codexvalidator/blocks.nim
+++ b/codexvalidator/blocks.nim
@@ -7,3 +7,7 @@ export blck
 import ./blocks/serialization
 
 export serialization.toBytes
+
+import ./blocks/blockhash
+
+export blockhash.id
diff --git a/codexvalidator/blocks/blck.nim b/codexvalidator/blocks/blck.nim
index ba0e1b5..e3a87cc 100644
--- a/codexvalidator/blocks/blck.nim
+++ b/codexvalidator/blocks/blck.nim
@@ -1,12 +1,15 @@
-import pkg/mysticeti
+from pkg/mysticeti import CommitteeMember, `==`
+import ../basics
 import ../transaction
+import ../hashing
 import ./blockid
 
 export mysticeti.CommitteeMember
+export mysticeti.`==`
 
 type Block* = ref object
   author*: CommitteeMember
   round*: uint64
-  parents*: seq[blockid.BlockId]
+  parents*: seq[BlockId]
   transactions*: seq[Transaction]
-  id*: blockid.BlockId
+  hash*: ?Hash
diff --git a/codexvalidator/blocks/blockhash.nim b/codexvalidator/blocks/blockhash.nim
new file mode 100644
index 0000000..ebdec38
--- /dev/null
+++ b/codexvalidator/blocks/blockhash.nim
@@ -0,0 +1,15 @@
+import ../basics
+import ./blck
+import ./blockid
+import ./serialization
+import ../hashing
+
+func id*(blck: Block): BlockId =
+  without var hash =? blck.hash:
+    hash = Hash.hash(blck.toBytes())
+    blck.hash = some hash
+  BlockId.init(
+    blck.author,
+    blck.round,
+    hash
+  )
diff --git a/tests/codexvalidator/basics.nim b/tests/codexvalidator/basics.nim
index 2ebfcb4..f8e4c5b 100644
--- a/tests/codexvalidator/basics.nim
+++ b/tests/codexvalidator/basics.nim
@@ -1,11 +1,11 @@
 import std/unittest
-
-export unittest
-
 import std/sequtils
-
-export sequtils
-
 import pkg/stint
 
+export unittest
+export sequtils
 export stint
+
+import ./examples
+
+export examples
diff --git a/tests/codexvalidator/blocks/testBlock.nim b/tests/codexvalidator/blocks/testBlock.nim
new file mode 100644
index 0000000..a746c9e
--- /dev/null
+++ b/tests/codexvalidator/blocks/testBlock.nim
@@ -0,0 +1,12 @@
+import ../basics
+import codexvalidator/blocks
+import codexvalidator/hashing
+
+suite "Blocks":
+
+  test "have a correct block id":
+    let blck = Block.example
+    check blck.id.author == blck.author
+    check blck.id.round == blck.round
+    check blck.id.hash == Hash.hash(blck.toBytes())
+
diff --git a/tests/codexvalidator/blocks/testSerialization.nim b/tests/codexvalidator/blocks/testSerialization.nim
index a49cc5b..a4f2102 100644
--- a/tests/codexvalidator/blocks/testSerialization.nim
+++ b/tests/codexvalidator/blocks/testSerialization.nim
@@ -3,7 +3,6 @@ import codexvalidator/blocks
 import codexvalidator/blocks/serialization
 import codexvalidator/transaction/serialization
 import codexvalidator/hashing
-import ../examples
 
 suite "Block serialization":
 
diff --git a/tests/codexvalidator/testSignatures.nim b/tests/codexvalidator/testSignatures.nim
index ffad4dd..20fdbea 100644
--- a/tests/codexvalidator/testSignatures.nim
+++ b/tests/codexvalidator/testSignatures.nim
@@ -1,7 +1,6 @@
 import ./basics
 import pkg/blscurve
 import codexvalidator/signatures
-import ./examples
 
 suite "Signature scheme":
 
diff --git a/tests/codexvalidator/transaction/testSerialization.nim b/tests/codexvalidator/transaction/testSerialization.nim
index 1d48380..cd15e9f 100644
--- a/tests/codexvalidator/transaction/testSerialization.nim
+++ b/tests/codexvalidator/transaction/testSerialization.nim
@@ -1,7 +1,6 @@
 import ../basics
 import codexvalidator/transaction
 import codexvalidator/transaction/serialization
-import ../examples
 
 suite "Transaction serialization":
 
diff --git a/tests/codexvalidator/transaction/testSigning.nim b/tests/codexvalidator/transaction/testSigning.nim
index 7589940..e0b4694 100644
--- a/tests/codexvalidator/transaction/testSigning.nim
+++ b/tests/codexvalidator/transaction/testSigning.nim
@@ -1,7 +1,6 @@
 import ../basics
 import codexvalidator/signatures
 import codexvalidator/transaction
-import ../examples
 
 suite "Transaction signing":
 
diff --git a/tests/codexvalidator/transaction/testTransaction.nim b/tests/codexvalidator/transaction/testTransaction.nim
index bfc82a5..1d76b5c 100644
--- a/tests/codexvalidator/transaction/testTransaction.nim
+++ b/tests/codexvalidator/transaction/testTransaction.nim
@@ -1,6 +1,5 @@
 import ../basics
 import codexvalidator/transaction
-import ../examples
 
 suite "Transaction":
 
diff --git a/tests/tests.nim b/tests/tests.nim
index 42c33c8..a48f16d 100644
--- a/tests/tests.nim
+++ b/tests/tests.nim
@@ -2,6 +2,7 @@ import ./codexvalidator/testSignatures
 import ./codexvalidator/transaction/testTransaction
 import ./codexvalidator/transaction/testSigning
 import ./codexvalidator/transaction/testSerialization
+import ./codexvalidator/blocks/testBlock
 import ./codexvalidator/blocks/testSerialization
 
 {.warning[UnusedImport]:off.}