Add .toBeFalsy and .toBeTruthy

Summary:
Changelog: [Internal]
Add missing jest expect apis

Differential Revision: D69119852

packages/react-native-fantom/runtime/expect.js

@@ -144,6 +144,24 @@ class Expect {
     }
   }
 
+  toBeFalsy(): void {
+    const pass = Boolean(this.#received) === false;
+    if (!this.#isExpectedResult(pass)) {
+      throw new ErrorWithCustomBlame(
+        `Expected ${String(this.#received)}${this.#maybeNotLabel()} to be falsy`,
+      ).blameToPreviousFrame();
+    }
+  }
+
+  toBeTruthy(): void {
+    const pass = Boolean(this.#received);
+    if (!this.#isExpectedResult(pass)) {
+      throw new ErrorWithCustomBlame(
+        `Expected ${String(this.#received)}${this.#maybeNotLabel()} to be truthy`,
+      ).blameToPreviousFrame();
+    }
+  }
+
   toThrow(expected?: string): void {
     if (expected != null && typeof expected !== 'string') {
       throw new ErrorWithCustomBlame(

packages/react-native-fantom/src/__tests__/expect-itest.js

@@ -178,6 +178,29 @@ describe('expect', () => {
     }).toThrow();
   });
 
+  test('toBeFalsy', () => {
+    expect(false).toBeFalsy();
+    expect(0).toBeFalsy();
+    expect('').toBeFalsy();
+    expect(null).toBeFalsy();
+    expect(undefined).toBeFalsy();
+    expect(NaN).toBeFalsy();
+    expect([]).not.toBeFalsy();
+    expect(['']).not.toBeFalsy();
+  });
+
+  test('toBeTruthy', () => {
+    expect(true).toBeTruthy();
+    expect([]).toBeTruthy();
+    expect('a').toBeTruthy();
+    expect(false).not.toBeTruthy();
+    expect(0).not.toBeTruthy();
+    expect('').not.toBeTruthy();
+    expect(null).not.toBeTruthy();
+    expect(undefined).not.toBeTruthy();
+    expect(NaN).not.toBeTruthy();
+  });
+
   ['toBeCalled', 'toHaveBeenCalled'].map(toHaveBeenCalledAlias =>
     test(toHaveBeenCalledAlias, () => {
       const fn = jest.fn();