feat(test): add mock for Node.contains()

Author: manucorporat

src/mock-doc/node.ts

@@ -103,6 +103,10 @@ export class MockNode {
     return null;
   }
 
+  contains(otherNode: MockNode) {
+    return this.childNodes.includes(otherNode);
+  }
+
   removeChild(childNode: MockNode) {
     const index = this.childNodes.indexOf(childNode);
     if (index > -1) {

src/mock-doc/test/element.spec.ts

@@ -11,7 +11,9 @@ describe('element', () => {
     const elmParent = document.createElement('div');
     const elmChild = document.createElement('div');
     elmParent.appendChild(elmChild);
+    expect(document.body.contains(elmParent)).toBe(false);
     document.body.appendChild(elmParent);
+    expect(document.body.contains(elmParent)).toBe(true);
     expect(elmParent.isConnected).toBe(true);
     expect(elmChild.isConnected).toBe(true);
     expect(document.body.isConnected).toBe(true);