DRIVERS-1958: Do not expect readConcern for pre-4.2 servers (#1081)

aggregate-write-readPreference tests use client-level readConcern and writeConcern options to assert that they are still inherited and passed in the aggregate command; however, readConcern is generally not supported for write stages in server versions prior to 4.2.

As noted in the test comments, pre-4.2 servers may still allow a "local" read concern anyway, but some drivers may avoid inheriting a client-level read concern for pre-4.2. Skipping these tests for pre-4.2 servers avoids any ambiguity.

Author: jmikola

source/crud/tests/unified/aggregate-write-readPreference.json

@@ -181,6 +181,7 @@
       "description": "Aggregate with $out omits read preference for pre-5.0 server",
       "runOnRequirements": [
         {
+          "minServerVersion": "4.2",
           "maxServerVersion": "4.4.99",
           "serverless": "forbid"
         }

source/crud/tests/unified/aggregate-write-readPreference.yml

@@ -87,7 +87,11 @@ tests:
 
   - description: "Aggregate with $out omits read preference for pre-5.0 server"
     runOnRequirements:
-      - maxServerVersion: "4.4.99"
+      # MongoDB 4.2 introduced support for read concerns and write stages.
+      # Pre-4.2 servers may allow a "local" read concern anyway, but some
+      # drivers may avoid inheriting a client-level read concern for pre-4.2.
+      - minServerVersion: "4.2"
+        maxServerVersion: "4.4.99"
         serverless: "forbid"
     operations:
       - object: *collection0

source/crud/tests/unified/db-aggregate-write-readPreference.json

@@ -158,6 +158,7 @@
       "description": "Database-level aggregate with $out omits read preference for pre-5.0 server",
       "runOnRequirements": [
         {
+          "minServerVersion": "4.2",
           "maxServerVersion": "4.4.99",
           "serverless": "forbid"
         }

source/crud/tests/unified/db-aggregate-write-readPreference.yml

@@ -81,7 +81,11 @@ tests:
 
   - description: "Database-level aggregate with $out omits read preference for pre-5.0 server"
     runOnRequirements:
-      - maxServerVersion: "4.4.99"
+      # MongoDB 4.2 introduced support for read concerns and write stages.
+      # Pre-4.2 servers may allow a "local" read concern anyway, but some
+      # drivers may avoid inheriting a client-level read concern for pre-4.2.
+      - minServerVersion: "4.2"
+        maxServerVersion: "4.4.99"
         serverless: "forbid"
     operations:
       - object: *database0