ReduxRoutine: Improve isGenerator accuracy

packages/redux-routine/src/is-generator.js

@@ -1,10 +1,15 @@
 /**
  * Returns true if the given object is a generator, or false otherwise.
  *
+ * @link https://www.ecma-international.org/ecma-262/6.0/#sec-generator-objects
+ *
  * @param {*} object Object to test.
  *
  * @return {boolean} Whether object is a generator.
  */
 export default function isGenerator( object ) {
-	return !! object && typeof object.next === 'function';
+	return (
+		object &&
+		object[ Symbol.toStringTag ] === 'Generator'
+	);
 }

packages/redux-routine/src/test/is-generator.js

@@ -17,6 +17,18 @@ describe( 'isGenerator', () => {
 		} );
 	} );
 
+	it( 'should return false if an imposter!', () => {
+		const value = { next() {} };
+
+		expect( isGenerator( value ) ).toBe( false );
+	} );
+
+	it( 'should return false if an async generator', () => {
+		const value = ( async function* () {}() );
+
+		expect( isGenerator( value ) ).toBe( false );
+	} );
+
 	it( 'should return true if a generator', () => {
 		const value = ( function* () {}() );