diff --git a/backend/src/Model/spec/TreeNode.spec.ts b/backend/src/Model/spec/TreeNode.spec.ts
index 05d1cb9..7534e58 100644
--- a/backend/src/Model/spec/TreeNode.spec.ts
+++ b/backend/src/Model/spec/TreeNode.spec.ts
@@ -2,8 +2,11 @@ import 'mocha'
 
 import { TreeNodeFactory } from  '../'
 import { expect } from 'chai'
+import { Base64Message } from '../Base64Message';
 
 describe('TreeNode', () => {
+  const number3 = Base64Message.fromString("3")
+  const number5 = Base64Message.fromString("5")
   it('firstNode should retrieve first node', () => {
     const topics = 'foo/bar'.split('/')
     const leaf = TreeNodeFactory.fromEdgesAndValue(topics, undefined)
@@ -13,40 +16,40 @@ describe('TreeNode', () => {
 
   it('updateWithNode should update value', () => {
     const topics = 'foo/bar'.split('/')
-    const leaf = TreeNodeFactory.fromEdgesAndValue(topics, '3')
-    expect(leaf.message && leaf.message.value).to.eq('3')
-    const updateLeave = TreeNodeFactory.fromEdgesAndValue(topics, '5')
+    const leaf = TreeNodeFactory.fromEdgesAndValue(topics, Base64Message.fromString('3'))
+    expect(Base64Message.toUnicodeString(leaf.message!.value!)).to.eq('3')
+    const updateLeave = TreeNodeFactory.fromEdgesAndValue(topics, Base64Message.fromString('5'))
 
     const root = leaf.firstNode()
     root.updateWithNode(updateLeave.firstNode())
 
     expect(root.sourceEdge).to.eq(undefined)
-    expect(leaf.message && leaf.message.value).to.eq('5')
+    expect(Base64Message.toUnicodeString(leaf.message!.value!)).to.eq('5')
   })
 
   it('updateWithNode should update intermediate nodes', () => {
     const topics1 = 'foo/bar/baz'.split('/')
-    const leaf = TreeNodeFactory.fromEdgesAndValue(topics1, '3')
-    expect(leaf.message && leaf.message.value).to.eq('3')
+    const leaf = TreeNodeFactory.fromEdgesAndValue(topics1, Base64Message.fromString('3'))
+    expect(Base64Message.toUnicodeString(leaf.message!.value!)).to.eq('3')
 
     const topics2 = 'foo/bar'.split('/')
-    const updateLeave = TreeNodeFactory.fromEdgesAndValue(topics2, '5')
+    const updateLeave = TreeNodeFactory.fromEdgesAndValue(topics2, Base64Message.fromString('5'))
     leaf.firstNode().updateWithNode(updateLeave.firstNode())
 
     const barNode = leaf.firstNode().findNode('foo/bar')
     expect(barNode && barNode.sourceEdge && barNode.sourceEdge.name).to.eq('bar')
-    expect(barNode && barNode.message && barNode.message.value).to.eq('5')
+    expect(Base64Message.toUnicodeString(barNode!.message!.value!)).to.eq('5')
 
     expect(leaf.sourceEdge && leaf.sourceEdge.name).to.eq('baz')
-    expect(leaf.message && leaf.message.value).to.eq('3')
+    expect(Base64Message.toUnicodeString(leaf.message!.value!)).to.eq('3')
   })
 
   it('updateWithNode should add nodes to the tree', () => {
     const topics1 = 'foo/bar'.split('/')
-    const leaf1 = TreeNodeFactory.fromEdgesAndValue(topics1, 'foo')
+    const leaf1 = TreeNodeFactory.fromEdgesAndValue(topics1, Base64Message.fromString('foo'))
 
     const topics2 = 'foo/bar/baz'.split('/')
-    const leaf2 = TreeNodeFactory.fromEdgesAndValue(topics2, 'bar')
+    const leaf2 = TreeNodeFactory.fromEdgesAndValue(topics2, Base64Message.fromString('bar'))
 
     leaf1.firstNode().updateWithNode(leaf2.firstNode())
 
diff --git a/backend/src/Model/spec/TreeNodeFactory.spec.ts b/backend/src/Model/spec/TreeNodeFactory.spec.ts
index a7f488a..2055bba 100644
--- a/backend/src/Model/spec/TreeNodeFactory.spec.ts
+++ b/backend/src/Model/spec/TreeNodeFactory.spec.ts
@@ -2,6 +2,7 @@ import 'mocha'
 
 import { TreeNodeFactory } from '../'
 import { expect } from 'chai'
+import { Base64Message } from '../Base64Message';
 
 describe('TreeNodeFactory', () => {
   it('root node must not have a sourceEdge', () => {
@@ -15,7 +16,7 @@ describe('TreeNodeFactory', () => {
   it('should create node', () => {
     const topic = 'foo/bar'
     const edges = topic.split('/')
-    const node = TreeNodeFactory.fromEdgesAndValue(edges, '5')
+    const node = TreeNodeFactory.fromEdgesAndValue(edges, Base64Message.fromString('5'))
 
     if (!node.sourceEdge || !node.sourceEdge.source || !node.message) {
       expect.fail('should not happen')
@@ -24,7 +25,7 @@ describe('TreeNodeFactory', () => {
 
     expect(node).to.not.eq(undefined)
     expect(node.sourceEdge.name).to.eq('bar')
-    expect(node.message.value).to.eq('5')
+    expect(Base64Message.toUnicodeString(node.message.value!)).to.eq('5')
 
     const foo = node.firstNode().findNode('foo')
     expect(foo && foo.sourceEdge && foo.sourceEdge.name).to.eq('foo')
@@ -33,14 +34,14 @@ describe('TreeNodeFactory', () => {
   it('node should contain edges in order', () => {
     const topic = 'foo/bar/baz'
     const edges = topic.split('/')
-    const node = TreeNodeFactory.fromEdgesAndValue(edges, '5')
+    const node = TreeNodeFactory.fromEdgesAndValue(edges, Base64Message.fromString('5'))
 
     if (!node.sourceEdge || !node.sourceEdge.source || !node.message) {
       expect.fail('should not happen')
       return
     }
 
-    expect(node.message.value).to.eq('5')
+    expect(Base64Message.toUnicodeString(node.message.value!)).to.eq('5')
     expect(node.sourceEdge.name).to.eq('baz')
 
     const barNode = node.sourceEdge.source