test: add failing test for ReactiveX#5237

spec/operators/finalize-spec.ts

@@ -1,8 +1,9 @@
 import { expect } from 'chai';
-import { finalize, map, share } from 'rxjs/operators';
+import { finalize, first, map, share } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
 import { hot, cold, expectObservable, expectSubscriptions } from '../helpers/marble-testing';
-import { of, timer, interval } from 'rxjs';
+import { of, timer, interval, NEVER } from 'rxjs';
+import { asInteropOperator } from '../helpers/interop-helper';
 
 declare const type: Function;
 
@@ -161,4 +162,18 @@ describe('finalize operator', () => {
     rxTestScheduler.flush();
     expect(executed).to.be.true;
   });
+
+  it('should handle interop sources', (done: MochaDone) => {
+    // See https://github.com/ReactiveX/rxjs/issues/5237
+    let completed = false;
+    NEVER.pipe(
+      asInteropOperator(finalize(() => {
+        expect(completed).to.be.true;
+        done();
+      })),
+      asInteropOperator(first())
+    ).subscribe(null, null, () => {
+      completed = true;
+    });
+  });
 });