feat: add rerender method (#257)

BREAKING CHANGE:

`rerender` has been renamed to `change`.
The `change` method keeps the current fixture intact and invokes `ngOnChanges`.

The new `rerender` method destroys the current component and creates a new instance with the updated properties.

BEFORE:

```ts
const { rerender } = render(...)
rerender({...})
```

AFTER:

```ts
const { change } = render(...)
change({...})
```

Author: timdeschryver

Diff for: apps/example-app-karma/src/app/issues/issue-222.spec.ts

@@ -1,14 +1,28 @@
 import { render, screen } from '@testing-library/angular';
 
-it('https://github.com/testing-library/angular-testing-library/issues/222', async () => {
+it('https://github.com/testing-library/angular-testing-library/issues/222 with rerender', async () => {
   const { rerender } = await render(`<div>Hello {{ name}}</div>`, {
     componentProperties: {
       name: 'Sarah',
     },
   });
 
   expect(screen.getByText('Hello Sarah')).toBeTruthy();
-  rerender({ name: 'Mark' });
+
+  await rerender({ name: 'Mark' });
+
+  expect(screen.getByText('Hello Mark')).toBeTruthy();
+});
+
+it('https://github.com/testing-library/angular-testing-library/issues/222 with change', async () => {
+  const { change } = await render(`<div>Hello {{ name}}</div>`, {
+    componentProperties: {
+      name: 'Sarah',
+    },
+  });
+
+  expect(screen.getByText('Hello Sarah')).toBeTruthy();
+  await change({ name: 'Mark' });
 
   expect(screen.getByText('Hello Mark')).toBeTruthy();
 });

Diff for: apps/example-app/src/app/examples/16-input-getter-setter.spec.ts

@@ -10,16 +10,29 @@ test('should run logic in the input setter and getter', async () => {
   expect(getterValueControl).toHaveTextContent('I am value from getter Angular');
 });
 
-test('should run logic in the input setter and getter while re-rendering', async () => {
-  const { rerender } = await render(InputGetterSetter, { componentProperties: { value: 'Angular' } });
+test('should run logic in the input setter and getter while changing', async () => {
+  const { change } = await render(InputGetterSetter, { componentProperties: { value: 'Angular' } });
   const valueControl = screen.getByTestId('value');
   const getterValueControl = screen.getByTestId('value-getter');
 
   expect(valueControl).toHaveTextContent('I am value from setter Angular');
   expect(getterValueControl).toHaveTextContent('I am value from getter Angular');
 
-  await rerender({ value: 'React' });
+  await change({ value: 'React' });
 
   expect(valueControl).toHaveTextContent('I am value from setter React');
   expect(getterValueControl).toHaveTextContent('I am value from getter React');
 });
+
+test('should run logic in the input setter and getter while re-rendering', async () => {
+  const { rerender } = await render(InputGetterSetter, { componentProperties: { value: 'Angular' } });
+
+  expect(screen.getByTestId('value')).toHaveTextContent('I am value from setter Angular');
+  expect(screen.getByTestId('value-getter')).toHaveTextContent('I am value from getter Angular');
+
+  await rerender({ value: 'React' });
+
+  // note we have to re-query because the elements are not the same anymore
+  expect(screen.getByTestId('value')).toHaveTextContent('I am value from setter React');
+  expect(screen.getByTestId('value-getter')).toHaveTextContent('I am value from getter React');
+});

Diff for: projects/testing-library/src/lib/models.ts

@@ -54,9 +54,16 @@ export interface RenderResult<ComponentType, WrapperType = ComponentType> extend
   navigate: (elementOrPath: Element | string, basePath?: string) => Promise<boolean>;
   /**
    * @description
-   * Re-render the same component with different props.
+   * Re-render the same component with different properties.
+   * This creates a new instance of the component.
    */
-  rerender: (componentProperties: Partial<ComponentType>) => void;
+  rerender: (rerenderedProperties: Partial<ComponentType>) => void;
+
+  /**
+   * @description
+   * Keeps the current fixture intact and invokes ngOnChanges with the updated properties.
+   */
+  change: (changedProperties: Partial<ComponentType>) => void;
 }
 
 export interface RenderComponentOptions<ComponentType, Q extends Queries = typeof queries> {

Diff for: projects/testing-library/src/lib/testing-library.ts

@@ -97,53 +97,30 @@ export async function render<SutType, WrapperType = SutType>(
     schemas: [...schemas],
   });
 
-  if (componentProviders) {
-    componentProviders
-      .reduce((acc, provider) => acc.concat(provider), [])
-      .forEach((p) => {
-        const { provide, ...provider } = p;
-        TestBed.overrideProvider(provide, provider);
-      });
-  }
-
-  const fixture = await createComponentFixture(sut, { template, wrapper });
-  setComponentProperties(fixture, { componentProperties });
-
-  if (removeAngularAttributes) {
-    fixture.nativeElement.removeAttribute('ng-version');
-    const idAttribute = fixture.nativeElement.getAttribute('id');
-    if (idAttribute && idAttribute.startsWith('root')) {
-      fixture.nativeElement.removeAttribute('id');
-    }
-  }
-
-  mountedFixtures.add(fixture);
-
   await TestBed.compileComponents();
 
-  let isAlive = true;
-  fixture.componentRef.onDestroy(() => (isAlive = false));
+  componentProviders
+    .reduce((acc, provider) => acc.concat(provider), [])
+    .forEach((p) => {
+      const { provide, ...provider } = p;
+      TestBed.overrideProvider(provide, provider);
+    });
 
-  function detectChanges() {
-    if (isAlive) {
-      fixture.detectChanges();
-    }
-  }
+  const componentContainer = createComponentFixture(sut, { template, wrapper });
 
-  // Call ngOnChanges on initial render
-  if (hasOnChangesHook(fixture.componentInstance)) {
-    const changes = getChangesObj(null, componentProperties);
-    fixture.componentInstance.ngOnChanges(changes);
-  }
+  let fixture: ComponentFixture<SutType>;
+  let detectChanges: () => void;
 
-  if (detectChangesOnRender) {
-    detectChanges();
-  }
+  await renderFixture(componentProperties);
+
+  const rerender = async (rerenderedProperties: Partial<SutType>) => {
+    await renderFixture(rerenderedProperties);
+  };
 
-  const rerender = (rerenderedProperties: Partial<SutType>) => {
-    const changes = getChangesObj(fixture.componentInstance, rerenderedProperties);
+  const change = (changedProperties: Partial<SutType>) => {
+    const changes = getChangesObj(fixture.componentInstance, changedProperties);
 
-    setComponentProperties(fixture, { componentProperties: rerenderedProperties });
+    setComponentProperties(fixture, { componentProperties: changedProperties });
 
     if (hasOnChangesHook(fixture.componentInstance)) {
       fixture.componentInstance.ngOnChanges(changes);
@@ -192,9 +169,10 @@ export async function render<SutType, WrapperType = SutType>(
 
   return {
     fixture,
-    detectChanges,
+    detectChanges: () => detectChanges(),
     navigate,
     rerender,
+    change,
     debugElement: typeof sut === 'string' ? fixture.debugElement : fixture.debugElement.query(By.directive(sut)),
     container: fixture.nativeElement,
     debug: (element = fixture.nativeElement, maxLength, options) =>
@@ -203,6 +181,42 @@ export async function render<SutType, WrapperType = SutType>(
         : console.log(dtlPrettyDOM(element, maxLength, options)),
     ...replaceFindWithFindAndDetectChanges(dtlGetQueriesForElement(fixture.nativeElement, queries)),
   };
+
+  async function renderFixture(properties: Partial<SutType>) {
+    if (fixture) {
+      cleanupAtFixture(fixture);
+    }
+
+    fixture = await createComponent(componentContainer);
+    setComponentProperties(fixture, { componentProperties: properties });
+
+    if (removeAngularAttributes) {
+      fixture.nativeElement.removeAttribute('ng-version');
+      const idAttribute = fixture.nativeElement.getAttribute('id');
+      if (idAttribute && idAttribute.startsWith('root')) {
+        fixture.nativeElement.removeAttribute('id');
+      }
+    }
+    mountedFixtures.add(fixture);
+
+    let isAlive = true;
+    fixture.componentRef.onDestroy(() => (isAlive = false));
+
+    if (hasOnChangesHook(fixture.componentInstance)) {
+      const changes = getChangesObj(null, componentProperties);
+      fixture.componentInstance.ngOnChanges(changes);
+    }
+
+    detectChanges = () => {
+      if (isAlive) {
+        fixture.detectChanges();
+      }
+    };
+
+    if (detectChangesOnRender) {
+      detectChanges();
+    }
+  }
 }
 
 async function createComponent<SutType>(component: Type<SutType>): Promise<ComponentFixture<SutType>> {
@@ -211,19 +225,19 @@ async function createComponent<SutType>(component: Type<SutType>): Promise<Compo
   return TestBed.createComponent(component);
 }
 
-async function createComponentFixture<SutType>(
+function createComponentFixture<SutType>(
   sut: Type<SutType> | string,
   { template, wrapper }: Pick<RenderDirectiveOptions<any>, 'template' | 'wrapper'>,
-): Promise<ComponentFixture<SutType>> {
+): Type<any> {
   if (typeof sut === 'string') {
     TestBed.overrideTemplate(wrapper, sut);
-    return createComponent(wrapper);
+    return wrapper;
   }
   if (template) {
     TestBed.overrideTemplate(wrapper, template);
-    return createComponent(wrapper);
+    return wrapper;
   }
-  return createComponent(sut);
+  return sut;
 }
 
 function setComponentProperties<SutType>(

Diff for: projects/testing-library/tests/change.spec.ts

@@ -0,0 +1,85 @@
+import { ChangeDetectionStrategy, Component, Input, OnChanges, SimpleChanges } from '@angular/core';
+import { render, screen } from '../src/public_api';
+
+@Component({
+  selector: 'atl-fixture',
+  template: ` {{ firstName }} {{ lastName }} `,
+})
+class FixtureComponent {
+  @Input() firstName = 'Sarah';
+  @Input() lastName;
+}
+
+test('changes the component with updated props', async () => {
+  const { change } = await render(FixtureComponent);
+  expect(screen.getByText('Sarah')).toBeInTheDocument();
+
+  const firstName = 'Mark';
+  change({ firstName });
+
+  expect(screen.getByText(firstName)).toBeInTheDocument();
+});
+
+test('changes the component with updated props while keeping other props untouched', async () => {
+  const firstName = 'Mark';
+  const lastName = 'Peeters';
+  const { change } = await render(FixtureComponent, {
+    componentProperties: {
+      firstName,
+      lastName,
+    },
+  });
+
+  expect(screen.getByText(`${firstName} ${lastName}`)).toBeInTheDocument();
+
+  const firstName2 = 'Chris';
+  change({ firstName: firstName2 });
+
+  expect(screen.getByText(`${firstName2} ${lastName}`)).toBeInTheDocument();
+});
+
+@Component({
+  selector: 'atl-fixture',
+  template: ` {{ name }} `,
+})
+class FixtureWithNgOnChangesComponent implements OnChanges {
+  @Input() name = 'Sarah';
+  @Input() nameChanged: (name: string, isFirstChange: boolean) => void;
+
+  ngOnChanges(changes: SimpleChanges) {
+    if (changes.name && this.nameChanged) {
+      this.nameChanged(changes.name.currentValue, changes.name.isFirstChange());
+    }
+  }
+}
+
+test('will call ngOnChanges on change', async () => {
+  const nameChanged = jest.fn();
+  const componentProperties = { nameChanged };
+  const { change } = await render(FixtureWithNgOnChangesComponent, { componentProperties });
+  expect(screen.getByText('Sarah')).toBeInTheDocument();
+
+  const name = 'Mark';
+  change({ name });
+
+  expect(screen.getByText(name)).toBeInTheDocument();
+  expect(nameChanged).toHaveBeenCalledWith(name, false);
+});
+
+@Component({
+  changeDetection: ChangeDetectionStrategy.OnPush,
+  selector: 'atl-fixture',
+  template: ` <div data-testid="number" [class.active]="activeField === 'number'">Number</div> `,
+})
+class FixtureWithOnPushComponent {
+  @Input() activeField: string;
+}
+
+test('update properties on change', async () => {
+  const { change } = await render(FixtureWithOnPushComponent);
+  const numberHtmlElementRef = screen.queryByTestId('number');
+
+  expect(numberHtmlElementRef).not.toHaveClass('active');
+  change({ activeField: 'number' });
+  expect(numberHtmlElementRef).toHaveClass('active');
+});