test: resize directive

app/javascript/dashboard/helper/specs/directives/resize.spec.js

@@ -0,0 +1,78 @@
+import resize from '../../directives/resize';
+
+class ResizeObserverMock {
+  // eslint-disable-next-line class-methods-use-this
+  observe() {}
+
+  // eslint-disable-next-line class-methods-use-this
+  unobserve() {}
+
+  // eslint-disable-next-line class-methods-use-this
+  disconnect() {}
+}
+
+describe('resize directive', () => {
+  let el;
+  let binding;
+  let observer;
+
+  beforeEach(() => {
+    el = document.createElement('div');
+    binding = {
+      value: jest.fn(),
+    };
+    observer = {
+      observe: jest.fn(),
+      unobserve: jest.fn(),
+      disconnect: jest.fn(),
+    };
+    window.ResizeObserver = ResizeObserverMock;
+    jest.spyOn(window, 'ResizeObserver').mockImplementation(() => observer);
+  });
+
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('should create ResizeObserver on bind', () => {
+    resize.bind(el, binding);
+
+    expect(ResizeObserver).toHaveBeenCalled();
+    expect(observer.observe).toHaveBeenCalledWith(el);
+  });
+
+  it('should call callback on observer callback', () => {
+    el = document.createElement('div');
+    binding = {
+      value: jest.fn(),
+    };
+
+    resize.bind(el, binding);
+
+    const entries = [{ contentRect: { width: 100, height: 100 } }];
+    const callback = binding.value;
+    callback(entries[0]);
+
+    expect(binding.value).toHaveBeenCalledWith(entries[0]);
+  });
+
+  it('should destroy and recreate observer on update', () => {
+    resize.bind(el, binding);
+
+    resize.update(el, { ...binding, oldValue: 'old' });
+
+    expect(observer.unobserve).toHaveBeenCalledWith(el);
+    expect(observer.disconnect).toHaveBeenCalled();
+    expect(ResizeObserver).toHaveBeenCalledTimes(2);
+    expect(observer.observe).toHaveBeenCalledTimes(2);
+  });
+
+  it('should destroy observer on unbind', () => {
+    resize.bind(el, binding);
+
+    resize.unbind(el);
+
+    expect(observer.unobserve).toHaveBeenCalledWith(el);
+    expect(observer.disconnect).toHaveBeenCalled();
+  });
+});