feat: toContainElement matcher (#1495)

* feat: add toContainElement matcher

* chore: replace printElement with formatElement

* chore: mimic jest-dom instead of jest-native

* fix: checking host element

* test: passing null as argument

* chore: rename basic test case

* test: negative case

* test: on null elements

* fix: validating host container and element

* refactor: code review changes

* refactor: tweaks

* refactors: cleanup

---------

Co-authored-by: Maciej Jastrzebski <mdjastrzebski@gmail.com>

Author: siepra

src/matchers/__tests__/to-contain-element.test.tsx

@@ -0,0 +1,141 @@
+import * as React from 'react';
+import { View } from 'react-native';
+import { render, screen } from '../..';
+import '../extend-expect';
+
+test('toContainElement() supports basic case', () => {
+  render(
+    <View testID="parent">
+      <View testID="child" />
+    </View>
+  );
+
+  const parent = screen.getByTestId('parent');
+  const child = screen.getByTestId('child');
+
+  expect(parent).toContainElement(child);
+
+  expect(() => expect(parent).not.toContainElement(child))
+    .toThrowErrorMatchingInlineSnapshot(`
+    "expect(container).not.toContainElement(element)
+
+      <View
+        testID="parent"
+      /> 
+
+    contains:
+
+       <View
+        testID="child"
+      />
+            "
+  `);
+});
+
+test('toContainElement() supports negative case', () => {
+  render(
+    <>
+      <View testID="view1" />
+      <View testID="view2" />
+    </>
+  );
+
+  const view1 = screen.getByTestId('view1');
+  const view2 = screen.getByTestId('view2');
+
+  expect(view1).not.toContainElement(view2);
+  expect(view2).not.toContainElement(view1);
+
+  expect(() => expect(view1).toContainElement(view2))
+    .toThrowErrorMatchingInlineSnapshot(`
+    "expect(container).toContainElement(element)
+
+      <View
+        testID="view1"
+      /> 
+
+    does not contain:
+
+       <View
+        testID="view2"
+      />
+            "
+  `);
+});
+
+test('toContainElement() handles null container', () => {
+  render(<View testID="view" />);
+
+  const view = screen.getByTestId('view');
+
+  expect(() => expect(null).toContainElement(view))
+    .toThrowErrorMatchingInlineSnapshot(`
+    "expect(received).toContainElement()
+
+    received value must be a host element.
+    Received has value: null"
+  `);
+});
+
+test('toContainElement() handles null element', () => {
+  render(<View testID="view" />);
+
+  const view = screen.getByTestId('view');
+
+  expect(view).not.toContainElement(null);
+
+  expect(() => expect(view).toContainElement(null))
+    .toThrowErrorMatchingInlineSnapshot(`
+    "expect(container).toContainElement(element)
+
+      <View
+        testID="view"
+      /> 
+
+    does not contain:
+
+       null
+            "
+  `);
+});
+
+test('toContainElement() handles non-element container', () => {
+  render(<View testID="view" />);
+
+  const view = screen.getByTestId('view');
+
+  expect(() => expect({ name: 'non-element' }).not.toContainElement(view))
+    .toThrowErrorMatchingInlineSnapshot(`
+    "expect(received).not.toContainElement()
+
+    received value must be a host element.
+    Received has type:  object
+    Received has value: {"name": "non-element"}"
+  `);
+
+  expect(() => expect(true).not.toContainElement(view))
+    .toThrowErrorMatchingInlineSnapshot(`
+      "expect(received).not.toContainElement()
+
+      received value must be a host element.
+      Received has type:  boolean
+      Received has value: true"
+    `);
+});
+
+test('toContainElement() handles non-element element', () => {
+  render(<View testID="view" />);
+
+  const view = screen.getByTestId('view');
+
+  expect(() =>
+    // @ts-expect-error
+    expect(view).not.toContainElement({ name: 'non-element' })
+  ).toThrowErrorMatchingInlineSnapshot(`
+    "expect(received).not.toContainElement()
+
+    received value must be a host element.
+    Received has type:  object
+    Received has value: {"name": "non-element"}"
+  `);
+});

src/matchers/extend-expect.d.ts

@@ -1,4 +1,5 @@
 import type { StyleProp } from 'react-native';
+import type { ReactTestInstance } from 'react-test-renderer';
 import type { TextMatch, TextMatchOptions } from '../matches';
 import type { Style } from './to-have-style';
 
@@ -12,6 +13,7 @@ export interface JestNativeMatchers<R> {
   toBePartiallyChecked(): R;
   toBeSelected(): R;
   toBeVisible(): R;
+  toContainElement(element: ReactTestInstance | null): R;
   toHaveDisplayValue(expectedValue: TextMatch, options?: TextMatchOptions): R;
   toHaveProp(name: string, expectedValue?: unknown): R;
   toHaveStyle(style: StyleProp<Style>): R;

src/matchers/extend-expect.ts

@@ -8,6 +8,7 @@ import { toBeEmptyElement } from './to-be-empty-element';
 import { toBePartiallyChecked } from './to-be-partially-checked';
 import { toBeSelected } from './to-be-selected';
 import { toBeVisible } from './to-be-visible';
+import { toContainElement } from './to-contain-element';
 import { toHaveDisplayValue } from './to-have-display-value';
 import { toHaveProp } from './to-have-prop';
 import { toHaveStyle } from './to-have-style';
@@ -23,6 +24,7 @@ expect.extend({
   toBePartiallyChecked,
   toBeSelected,
   toBeVisible,
+  toContainElement,
   toHaveDisplayValue,
   toHaveProp,
   toHaveStyle,

src/matchers/index.tsx

@@ -1,12 +1,13 @@
-export { toBeOnTheScreen } from './to-be-on-the-screen';
+export { toBeBusy } from './to-be-busy';
 export { toBeChecked } from './to-be-checked';
 export { toBeDisabled, toBeEnabled } from './to-be-disabled';
-export { toBeBusy } from './to-be-busy';
 export { toBeEmptyElement } from './to-be-empty-element';
+export { toBeOnTheScreen } from './to-be-on-the-screen';
 export { toBePartiallyChecked } from './to-be-partially-checked';
+export { toBeSelected } from './to-be-selected';
 export { toBeVisible } from './to-be-visible';
+export { toContainElement } from './to-contain-element';
 export { toHaveDisplayValue } from './to-have-display-value';
 export { toHaveProp } from './to-have-prop';
 export { toHaveStyle } from './to-have-style';
 export { toHaveTextContent } from './to-have-text-content';
-export { toBeSelected } from './to-be-selected';

src/matchers/to-contain-element.tsx

@@ -0,0 +1,38 @@
+import { ReactTestInstance } from 'react-test-renderer';
+import { matcherHint, RECEIVED_COLOR } from 'jest-matcher-utils';
+import { checkHostElement, formatElement } from './utils';
+
+export function toContainElement(
+  this: jest.MatcherContext,
+  container: ReactTestInstance,
+  element: ReactTestInstance | null
+) {
+  checkHostElement(container, toContainElement, this);
+
+  if (element !== null) {
+    checkHostElement(element, toContainElement, this);
+  }
+
+  let matches: ReactTestInstance[] = [];
+  if (element) {
+    matches = container.findAll((node) => node === element);
+  }
+
+  return {
+    pass: matches.length > 0,
+    message: () => {
+      return [
+        matcherHint(
+          `${this.isNot ? '.not' : ''}.toContainElement`,
+          'container',
+          'element'
+        ),
+        '',
+        RECEIVED_COLOR(`${formatElement(container)} ${
+          this.isNot ? '\n\ncontains:\n\n' : '\n\ndoes not contain:\n\n'
+        } ${formatElement(element)}
+        `),
+      ].join('\n');
+    },
+  };
+}