Add expectNullable and expectNotNullable to runtime tests (#5935)

## Summary

As in description, added nullcheck methods `expectNullable` and
`expectNotNullable` to runtime tests API.

## Test plan

Use either of the methods in any of existing runtime tests and run their
example.

app/src/examples/RuntimeTests/ReanimatedRuntimeTestsRunner/Matchers.ts

@@ -1,6 +1,6 @@
 import { getComparator } from './Comparators';
 import { appendWhiteSpaceToMatchLength, color } from './stringFormatUtils';
-import { ComparisonMode, OperationUpdate, TestCase, TestValue, TrackerCallCount } from './types';
+import { ComparisonMode, OperationUpdate, TestCase, TestValue, NullableTestValue, TrackerCallCount } from './types';
 
 type MatcherFunction = (
   currentValue: TestValue,
@@ -210,3 +210,15 @@ export class Matchers {
     return `Expected ${expected} snapshots, but received ${received} snapshots\n`;
   }
 }
+
+export function nullableMatch(currentValue: NullableTestValue, testCase: TestCase, negation: boolean = false) {
+  const pass = currentValue === null || currentValue === undefined;
+
+  const coloredExpected = color('nullable', 'green');
+  const coloredReceived = color(currentValue, 'red');
+  const message = `Expected${negation ? ' NOT' : ''} ${coloredExpected} received ${coloredReceived}`;
+
+  if ((!pass && !negation) || (pass && negation)) {
+    testCase.errors.push(message);
+  }
+}

app/src/examples/RuntimeTests/ReanimatedRuntimeTestsRunner/RuntimeTestsApi.ts

@@ -2,7 +2,7 @@ import { Component, ReactElement } from 'react';
 import { TestRunner } from './TestRunner';
 import { TestComponent } from './TestComponent';
 import type { SharedValue } from 'react-native-reanimated';
-import { TestConfiguration, TestValue } from './types';
+import { TestConfiguration, TestValue, NullableTestValue } from './types';
 
 export { Presets } from './Presets';
 
@@ -100,6 +100,14 @@ export function expect(value: TestValue) {
   return testRunner.expect(value);
 }
 
+export function expectNullable(currentValue: NullableTestValue) {
+  return testRunner.expectNullable(currentValue);
+}
+
+export function expectNotNullable(currentValue: NullableTestValue) {
+  return testRunner.expectNotNullable(currentValue);
+}
+
 export function configure(config: TestConfiguration) {
   return testRunner.configure(config);
 }

app/src/examples/RuntimeTests/ReanimatedRuntimeTestsRunner/TestRunner.ts

@@ -1,5 +1,6 @@
 import { Component, MutableRefObject, ReactElement, useRef } from 'react';
 import type {
+  NullableTestValue,
   LockObject,
   Operation,
   SharedValueSnapshot,
@@ -15,7 +16,7 @@ import { render, stopRecordingAnimationUpdates, unmockAnimationTimer } from './R
 import { makeMutable, runOnUI, runOnJS, SharedValue } from 'react-native-reanimated';
 import { color, formatString, indentNestingLevel } from './stringFormatUtils';
 import { createUpdatesContainer } from './UpdatesContainer';
-import { Matchers } from './Matchers';
+import { Matchers, nullableMatch } from './Matchers';
 import { assertMockedAnimationTimestamp, assertTestCase, assertTestSuite } from './Asserts';
 
 let callTrackerRegistryJS: Record<string, number> = {};
@@ -258,6 +259,16 @@ export class TestRunner {
     return new Matchers(currentValue, this._currentTestCase);
   }
 
+  public expectNullable(currentValue: NullableTestValue) {
+    assertTestCase(this._currentTestCase);
+    nullableMatch(currentValue, this._currentTestCase);
+  }
+
+  public expectNotNullable(currentValue: NullableTestValue) {
+    assertTestCase(this._currentTestCase);
+    nullableMatch(currentValue, this._currentTestCase, true);
+  }
+
   public beforeAll(job: () => void) {
     assertTestSuite(this._currentTestSuite);
     this._currentTestSuite.beforeAll = job;

app/src/examples/RuntimeTests/ReanimatedRuntimeTestsRunner/stringFormatUtils.ts

@@ -1,4 +1,4 @@
-import { TestValue } from './types';
+import { NullableTestValue } from './types';
 
 export const RUNTIME_TEST_ERRORS = {
   UNDEFINED_TEST_SUITE: 'Undefined test suite context',
@@ -16,7 +16,7 @@ export function appendWhiteSpaceToMatchLength(message: string | number, length:
   return `${messageStr}${' '.repeat(length - messageLen)}`;
 }
 
-export function color(value: TestValue, color: 'yellow' | 'cyan' | 'green' | 'red' | 'gray') {
+export function color(value: NullableTestValue, color: 'yellow' | 'cyan' | 'green' | 'red' | 'gray') {
   const COLOR_CODES = {
     red: '\x1b[31m',
     green: '\x1b[32m',

app/src/examples/RuntimeTests/ReanimatedRuntimeTestsRunner/types.ts

@@ -65,6 +65,7 @@ export interface Operation {
 }
 
 export type TestValue = TrackerCallCount | string | Array<unknown> | number | bigint | Record<string, unknown>;
+export type NullableTestValue = TestValue | null | undefined;
 
 export type TestConfiguration = {
   render: Dispatch<SetStateAction<ReactNode | null>>;