fix(searchFunction): Fix unresolved returned Promise (#2913)

* fix(searchFunction): Fix unresolved returned Promise
* test(searchFunction): Test `searchFunction` with multiple requests

Author: francoischalifour

src/lib/InstantSearch.js

@@ -314,7 +314,7 @@ Usage: instantsearch({
       helper.search = () => {
         const helperSearchFunction = algoliasearchHelper(
           {
-            search: () => Promise.resolve({ results: [{}] }),
+            search: () => new Promise(() => {}),
           },
           helper.state.index,
           helper.state

src/lib/__tests__/InstantSearch-test-2.js

@@ -159,4 +159,24 @@ describe('InstantSearch life cycle', () => {
 
     jest.runAllTimers();
   });
+
+  it('does not break when providing searchFunction with multiple resquests', () => {
+    const search = new InstantSearch({
+      appId,
+      apiKey,
+      indexName,
+      searchFunction: h => {
+        h.addDisjunctiveFacetRefinement('brand', 'Apple');
+        h.search();
+      },
+      searchParameters: {
+        disjunctiveFacetsRefinements: { brand: ['Apple'] },
+        disjunctiveFacets: ['brand'],
+      },
+    });
+
+    expect(() => {
+      search.start();
+    }).not.toThrow();
+  });
 });