adding new test for no notification when assigned the same value

packages/web-components/fast-foundation/src/design-token-2/design-token.spec.ts

@@ -93,6 +93,18 @@ describe.only("DesignTokenNode", () => {
         })
 
         describe("should not notify subscribers", () => {
+            it("when the value assigned is the same value", () => {
+                const token = DesignToken.create<number>("");
+                const node = new DesignTokenNode();
+                const handleChange = chai.spy(() => {})
+                const subscriber: Subscriber = { handleChange }
+                node.setTokenValue(token, 12);
+                Observable.getNotifier(token).subscribe(subscriber);
+
+                node.setTokenValue(token, 12);
+
+                expect(handleChange).not.to.have.been.called();
+            });
         });
     });
 

packages/web-components/fast-foundation/src/design-token-2/design-token.ts

@@ -64,6 +64,18 @@ class DynamicTokenValue<T> {
     }
 }
 
+interface DesignTokenChangeRecord<T> {
+    /**
+     * The token that changed
+     */
+    token: DesignToken<T>;
+
+    /**
+     * The token value
+     */
+    value: DesignTokenValue<T>;
+}
+
 export class DesignTokenNode {
     private _parent: DesignTokenNode | null = null;
     private _children: Set<DesignTokenNode> = new Set();
@@ -151,6 +163,11 @@ export class DesignTokenNode {
             throw new Error(`No value set for token ${token} in node tree.`);
         }
     }
+
+    /**
+     * Notifies the node that a token has changed for some ancestor.
+     */
+    private notify(records: DesignTokenChangeRecord<unknown>[]) {}
 }
 
 const nextId = (() => {