[TEST] add regular scroll REST test

Closes #7860

rest-api-spec/test/scroll/10_basic.yaml

@@ -1,14 +1,24 @@
 ---
-"Basic scroll":
+"Basic scan":
   - do:
       indices.create:
-          index:  test_scroll
+        index: test_scroll
+        body:
+          settings:
+            number_of_shards: "1"
+  - do:
+      index:
+        index:  test_scroll
+        type:   test
+        id:     42
+        body:   { foo: bar }
+
   - do:
       index:
-          index:  test_scroll
-          type:   test
-          id:     42
-          body:   { foo: bar }
+        index:  test_scroll
+        type:   test
+        id:     43
+        body:   { foo: bar }
 
   - do:
       indices.refresh: {}
@@ -17,16 +27,96 @@
       search:
         index: test_scroll
         search_type: scan
+        size: 1
         scroll: 1m
         body:
           query:
             match_all: {}
 
   - set: {_scroll_id: scroll_id}
+  - match: {hits.total:      2    }
+  - length: {hits.hits:      0    }
+
+  - do:
+      scroll:
+        scroll_id: $scroll_id
+        scroll: 1m
+
+  - set: {_scroll_id: scroll_id}
+  - match: {hits.total:      2    }
+  - length: {hits.hits: 1 }
 
   - do:
       scroll:
         scroll_id: $scroll_id
+        scroll: 1m
+
+  - set: {_scroll_id: scroll_id}
+  - match: {hits.total:      2    }
+  - length: {hits.hits: 1 }
+
+  - do:
+      scroll:
+        scroll_id: $scroll_id
+        scroll: 1m
+
+  - match: {hits.total:      2    }
+  - length: {hits.hits: 0 }
+
+---
+"Basic scroll":
+  - do:
+      indices.create:
+        index: test_scroll
+  - do:
+      index:
+        index:  test_scroll
+        type:   test
+        id:     42
+        body:   { foo: bar }
+
+  - do:
+      index:
+        index:  test_scroll
+        type:   test
+        id:     43
+        body:   { foo: bar }
+
+  - do:
+      indices.refresh: {}
+
+  - do:
+      search:
+        index: test_scroll
+        size: 1
+        scroll: 1m
+        body:
+          query:
+            match_all: {}
+
+  - set: {_scroll_id: scroll_id}
+  - match: {hits.total:      2    }
+  - length: {hits.hits:      1    }
+
+  - do:
+      index:
+        index:  test_scroll
+        type:   test
+        id:     42
+        body:   { foo: bar }
+
+  - do:
+      indices.refresh: {}
+
+  - do:
+      scroll:
+        scroll_id: $scroll_id
+        scroll: 1m
+
+  - match: {hits.total:      2    }
+  - length: {hits.hits:      1    }
+
+  - do:
+      clear_scroll:
+        scroll_id: $scroll_id
 
-  - match: {hits.total:      1    }
-  - match: {hits.hits.0._id: "42" }