test: lowercase returnDocument for spec tests

Author: dariakp

test/functional/crud_spec.test.js

@@ -320,6 +320,9 @@ describe('CRUD spec', function () {
     const filter = args.filter;
     const second = args.update || args.replacement;
     const options = Object.assign({}, args);
+    if (options.returnDocument) {
+      options.returnDocument = options.returnDocument.toLowerCase();
+    }
 
     delete options.filter;
     delete options.update;

test/functional/retryable_writes.test.js

@@ -136,8 +136,10 @@ function generateArguments(test) {
     Object.keys(test.operation.arguments).forEach(arg => {
       if (arg === 'requests') {
         args.push(test.operation.arguments[arg].map(convertBulkWriteOperation));
-      } else if (arg === 'upsert' || arg === 'returnDocument') {
-        options[arg] = test.operation.arguments[arg];
+      } else if (arg === 'upsert') {
+        options.upsert = test.operation.arguments[arg];
+      } else if (arg === 'returnDocument') {
+        options.returnDocument = test.operation.arguments[arg].toLowerCase();
       } else {
         args.push(test.operation.arguments[arg]);
       }

test/functional/spec-runner/index.js

@@ -680,6 +680,10 @@ function testOperation(operation, obj, context, options) {
             return;
           }
 
+          if (key === 'returnDocument') {
+            opOptions.returnDocument = operation.arguments[key].toLowerCase();
+          }
+
           if (key === 'options') {
             Object.assign(opOptions, operation.arguments[key]);
             if (opOptions.readPreference) {