RUBY-2876 Add test for let options for replace_one (#2405)

Author: comandeo-mongo

spec/runners/unified/crud_operations.rb

@@ -164,6 +164,7 @@ def replace_one(op)
           args.use!('filter'),
           args.use!('replacement'),
           upsert: args.use('upsert'),
+          let: args.use('let')
         )
       end
     end

spec/spec_tests/data/crud_unified/replaceOne-let.yml

@@ -0,0 +1,94 @@
+description: "replaceOne-let"
+
+schemaVersion: "1.0"
+
+createEntities:
+  - client:
+      id: &client0 client0
+      observeEvents: [ commandStartedEvent ]
+  - database:
+      id: &database0 database0
+      client: *client0
+      databaseName: &database0Name crud-tests
+  - collection:
+      id: &collection0 collection0
+      database: *database0
+      collectionName: &collection0Name coll0
+
+initialData: &initialData
+  - collectionName: *collection0Name
+    databaseName: *database0Name
+    documents:
+      - { _id: 1 }
+      - { _id: 2 }
+
+tests:
+  - description: "ReplaceOne with let option"
+    runOnRequirements:
+      - minServerVersion: "5.0"
+    operations:
+      - name: replaceOne
+        object: *collection0
+        arguments:
+          filter: &filter
+            $expr:
+              $eq: [ "$_id", "$$id" ]
+          replacement: &replacement
+            x: "foo"
+          let: &let
+            id: 1
+        expectResult:
+          matchedCount: 1
+          modifiedCount: 1
+          upsertedCount: 0
+    expectEvents:
+      - client: *client0
+        events:
+          - commandStartedEvent:
+              command:
+                update: *collection0Name
+                updates:
+                  -
+                    q: *filter
+                    u: *replacement
+                let: *let
+    outcome:
+      -
+        collectionName: *collection0Name
+        databaseName: *database0Name
+        documents:
+          - { _id: 1, x: "foo" }
+          - { _id: 2 }
+
+  - description: "ReplaceOne with let option unsupported (server-side error)"
+    runOnRequirements:
+      - minServerVersion: "3.6.0"
+        maxServerVersion: "4.4.99"
+    operations:
+      - name: replaceOne
+        object: *collection0
+        arguments:
+          filter: *filter
+          replacement: *replacement
+          let: *let
+        expectError:
+          errorContains: "'update.let' is an unknown field"
+          isClientError: false
+    expectEvents:
+      - client: *client0
+        events:
+          - commandStartedEvent:
+              command:
+                update: *collection0Name
+                updates:
+                  -
+                    q: *filter
+                    u: *replacement
+                let: *let
+    outcome:
+      -
+        collectionName: *collection0Name
+        databaseName: *database0Name
+        documents:
+          - { _id: 1 }
+          - { _id: 2 }