Fix flaky test in 91_flat_object_null_value.yml (#15545) (#15634)

This test assumed that the order of returned hits will match the order
of insertion. That's not generally true, especially if there was a
flush partway through, so documents end up in different segments.

This fixes it by explicitly sorting the returned documents to
guarantee that they come back in the correct order.

Also, we were getting a NPE when trying to output the failure message
because the expected value was intentionally null. I fixed that too.


(cherry picked from commit eb1cbb8)

Signed-off-by: Michael Froh <[email protected]>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: opensearch-trigger-bot[bot]

rest-api-spec/src/main/resources/rest-api-spec/test/index/91_flat_object_null_value.yml

@@ -16,12 +16,15 @@ setup:
             properties:
               record:
                 type: "flat_object"
+              order:
+                type: "integer"
   - do:
       index:
         index: flat_object_null_value
         id: 1
         body: {
-          "record": null
+          "record": null,
+          "order" : 1
         }
 
   - do:
@@ -31,7 +34,8 @@ setup:
         body: {
           "record": {
             "name": null
-          }
+          },
+          "order" : 2
         }
 
   - do:
@@ -43,7 +47,8 @@ setup:
             "name": null,
             "age":"5",
             "name1": null
-          }
+          },
+          "order" : 3
         }
 
   - do:
@@ -60,7 +65,8 @@ setup:
                 }
               }
             ]
-          }
+          },
+          "order" : 4
         }
 
   - do:
@@ -77,7 +83,8 @@ setup:
               },
               null
             ]
-          }
+          },
+          "order" : 5
         }
 
   - do:
@@ -97,7 +104,8 @@ setup:
                 }
               }
             ]
-          }
+          },
+          "order" : 6
         }
 
   - do:
@@ -108,7 +116,8 @@ setup:
           "record": {
             "name": null,
             "age":"3"
-          }
+          },
+          "order" : 7
         }
 
   - do:
@@ -119,7 +128,8 @@ setup:
           "record": {
             "age":"3",
             "name": null
-          }
+          },
+          "order" : 8
         }
 
   - do:
@@ -133,7 +143,8 @@ setup:
               3
             ],
             "age": 4
-          }
+          },
+          "order" : 9
         }
 
   - do:
@@ -147,7 +158,8 @@ setup:
               null,
               3
             ]
-          }
+          },
+          "order" : 10
         }
 
   - do:
@@ -157,7 +169,8 @@ setup:
         body: {
           "record": {
             "name": null
-          }
+          },
+          "order": 11
         }
 
   - do:
@@ -171,7 +184,8 @@ setup:
                 null
               ]
             }
-          }
+          },
+          "order": 12
         }
 
   - do:
@@ -183,7 +197,8 @@ setup:
             "labels": [
               null
             ]
-          }
+          },
+          "order": 13
         }
 
   - do:
@@ -198,7 +213,8 @@ setup:
                 null
               ]
             }
-          }
+          },
+          "order": 14
         }
 
   - do:
@@ -211,7 +227,8 @@ setup:
             "labels": [
               null
             ]
-          }
+          },
+          "order": 15
         }
 
   - do:
@@ -224,7 +241,8 @@ setup:
               null
             ],
             "age": "4"
-          }
+          },
+          "order": 16
         }
 
   - do:
@@ -239,7 +257,8 @@ setup:
                 "dsdsdsd"
               ]
             }
-          }
+          },
+          "order": 17
         }
 
   - do:
@@ -253,7 +272,8 @@ setup:
                 "name2": null
               }
             }
-          }
+          },
+          "order": 18
         }
 
   - do:
@@ -271,7 +291,8 @@ setup:
                 ]
               ]
             }
-          }
+          },
+          "order": 19
         }
 
   - do:
@@ -299,7 +320,7 @@ teardown:
   - is_true: flat_object_null_value.mappings
   - match: { flat_object_null_value.mappings.properties.record.type: flat_object }
   # https://github.com/opensearch-project/OpenSearch/tree/main/rest-api-spec/src/main/resources/rest-api-spec/test#length
-  - length: { flat_object_null_value.mappings.properties: 1 }
+  - length: { flat_object_null_value.mappings.properties: 2 }
 
 
 ---
@@ -328,7 +349,8 @@ teardown:
           size: 30,
           query: {
             exists: { "field": "record" }
-          }
+          },
+          sort: [{ order: asc}]
         }
 
   - length: { hits.hits: 12 }
@@ -352,7 +374,8 @@ teardown:
           _source: true,
           query: {
             exists: { "field": "record.d" }
-          }
+          },
+          sort: [{ order: asc}]
         }
 
   - length: { hits.hits: 3 }
@@ -367,7 +390,8 @@ teardown:
           _source: true,
           query: {
             term: { record: "dsdsdsd" }
-          }
+          },
+          sort: [{ order: asc}]
         }
 
   - length: { hits.hits: 2 }
@@ -381,7 +405,8 @@ teardown:
           _source: true,
           query: {
             term: { record.name.name1: "dsdsdsd" }
-          }
+          },
+          sort: [{ order: asc}]
         }
 
   - length: { hits.hits: 2 }

test/framework/src/main/java/org/opensearch/test/NotEqualMessageBuilder.java

@@ -181,18 +181,9 @@ public void compare(String field, boolean hadKey, @Nullable Object actual, Objec
             field(field, "same [" + expected + "]");
             return;
         }
-        field(
-            field,
-            "expected "
-                + expected.getClass().getSimpleName()
-                + " ["
-                + expected
-                + "] but was "
-                + actual.getClass().getSimpleName()
-                + " ["
-                + actual
-                + "]"
-        );
+        String expectedClass = expected == null ? "null object" : expected.getClass().getSimpleName();
+        String actualClass = actual == null ? "null object" : actual.getClass().getSimpleName();
+        field(field, "expected " + expectedClass + " [" + expected + "] but was " + actualClass + " [" + actual + "]");
     }
 
     private void indent() {