test: improve testing of default write concern

NODE-2291

test/functional/write_concern.test.js

@@ -0,0 +1,19 @@
+'use strict';
+
+const TestRunnerContext = require('./spec-runner').TestRunnerContext;
+const generateTopologyTests = require('./spec-runner').generateTopologyTests;
+const loadSpecTests = require('../spec').loadSpecTests;
+
+describe('Write Concern', function() {
+  describe('spec tests', function() {
+    const testContext = new TestRunnerContext();
+    const testSuites = loadSpecTests('read-write-concern/operation');
+
+    after(() => testContext.teardown());
+    before(function() {
+      return testContext.setup(this.configuration);
+    });
+
+    generateTopologyTests(testSuites, testContext);
+  });
+});