Add tests to not call the callback from unobserved nodes

package.json

@@ -1,6 +1,6 @@
 {
   "name": "jsdom-testing-mocks",
-  "version": "1.11.0",
+  "version": "1.12.0",
   "author": "Ivan Galiatin",
   "license": "MIT",
   "description": "A set of tools for emulating browser behavior in jsdom environment",

src/mocks/intersection-observer.test.ts

@@ -0,0 +1,68 @@
+import { mockIntersectionObserver } from './intersection-observer';
+
+const io = mockIntersectionObserver();
+
+describe('mockIntersectionObserver', () => {
+  it("don't call unobserved nodes, enterNode", () => {
+    const node = document.createElement('div');
+    const callback = runner.fn();
+
+    const observer = new IntersectionObserver(callback);
+
+    observer.observe(node);
+
+    io.enterNode(node);
+
+    expect(callback).toHaveBeenCalledTimes(1);
+
+    observer.unobserve(node);
+
+    io.enterNode(node);
+
+    expect(callback).toHaveBeenCalledTimes(1);
+  });
+
+  it('handles multiple nodes correctly, enterNodes', () => {
+    const node1 = document.createElement('div');
+    const node2 = document.createElement('div');
+    const callback = runner.fn();
+
+    const observer = new IntersectionObserver(callback);
+
+    observer.observe(node1);
+    observer.observe(node2);
+
+    io.enterNodes([node1, node2]);
+
+    expect(callback).toHaveBeenCalledTimes(1);
+
+    observer.unobserve(node1);
+    observer.unobserve(node2);
+
+    io.enterNodes([node1, node2]);
+
+    expect(callback).toHaveBeenCalledTimes(1);
+  });
+
+  it('handles multiple nodes correctly, enterAll', () => {
+    const node1 = document.createElement('div');
+    const node2 = document.createElement('div');
+    const callback = runner.fn();
+
+    const observer = new IntersectionObserver(callback);
+
+    observer.observe(node1);
+    observer.observe(node2);
+
+    io.enterAll();
+
+    expect(callback).toHaveBeenCalledTimes(1);
+
+    observer.unobserve(node1);
+    observer.unobserve(node2);
+
+    io.enterAll();
+
+    expect(callback).toHaveBeenCalledTimes(1);
+  });
+});