Add helpers to create database and client change streams.

GODRIVER-437
GODRIVER-469
GODRIVER-591

Change-Id: I52270279e9ea05c1e64e5ec3d9d8a86478cd9986

Author: Divjot Arora

data/change-streams/change-streams-errors.json

@@ -0,0 +1,78 @@
+{
+  "collection_name": "test",
+  "database_name": "change-stream-tests",
+  "collection2_name": "test2",
+  "database2_name": "change-stream-tests-2",
+  "tests": [
+    {
+      "description": "The watch helper must not throw a custom exception when executed against a single server topology, but instead depend on a server error",
+      "minServerVersion": "3.6.0",
+      "target": "collection",
+      "topology": [
+        "single"
+      ],
+      "changeStreamPipeline": [],
+      "changeStreamOptions": {},
+      "operations": [],
+      "expectations": [],
+      "result": {
+        "error": {
+          "code": 40573
+        }
+      }
+    },
+    {
+      "description": "Change Stream should error when an invalid aggregation stage is passed in",
+      "minServerVersion": "3.6.0",
+      "target": "collection",
+      "topology": [
+        "replicaset"
+      ],
+      "changeStreamPipeline": [
+        {
+          "$unsupported": "foo"
+        }
+      ],
+      "changeStreamOptions": {},
+      "operations": [
+        {
+          "database": "change-stream-tests",
+          "collection": "test",
+          "name": "insertOne",
+          "arguments": {
+            "document": {
+              "z": 3
+            }
+          }
+        }
+      ],
+      "expectations": [
+        {
+          "command_started_event": {
+            "command": {
+              "aggregate": "test",
+              "cursor": {},
+              "pipeline": [
+                {
+                  "$changeStream": {
+                    "fullDocument": "default"
+                  }
+                },
+                {
+                  "$unsupported": "foo"
+                }
+              ]
+            },
+            "command_name": "aggregate",
+            "database_name": "change-stream-tests"
+          }
+        }
+      ],
+      "result": {
+        "error": {
+          "code": 40324
+        }
+      }
+    }
+  ]
+}