add tests for Fantom.scheduleTask (#50033)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/50033

changelog: [internal]

All public APIs should be covered with tests, this diff adds tests for Fantom.scheduleTask.

Reviewed By: rubennorte

Differential Revision: D71195921

fbshipit-source-id: dc7f0f889b9633b1e641dc8887fd506bc4753fe5

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

@@ -829,3 +829,35 @@ describe('Fantom', () => {
     });
   });
 });
+
+describe('scheduleTask', () => {
+  it('does not run task immediately', () => {
+    let didRun = false;
+
+    Fantom.scheduleTask(() => {
+      didRun = true;
+    });
+
+    expect(didRun).toBe(false);
+
+    Fantom.runWorkLoop();
+
+    expect(didRun).toBe(true);
+  });
+
+  it('can be scheduled from within another task', () => {
+    let didInnerTaskRun = false;
+
+    Fantom.scheduleTask(() => {
+      Fantom.scheduleTask(() => {
+        didInnerTaskRun = true;
+      });
+    });
+
+    expect(didInnerTaskRun).toBe(false);
+
+    Fantom.runWorkLoop();
+
+    expect(didInnerTaskRun).toBe(true);
+  });
+});