make fixture await render if contents are attached

CHANGELOG.md

@@ -40,6 +40,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
   - mwc-floating-label-directive
   - mwc-top-app-bar-fixed
   - mwc-top-app-bar-short
+- Testing Infra:
+  - Tests now in TS
+  - Tests now all pass
+  -
 
 ## [0.6.0] - 2019-06-05
 - Upgrade lerna to 3.x

test/src/util/helpers.ts

@@ -89,13 +89,17 @@ interface FixtureOptions {
 }
 
 export const fixture =
-    (template: TemplateResult, options?: Partial<FixtureOptions>) => {
+    async (template: TemplateResult, options?: Partial<FixtureOptions>) => {
       const opts: FixtureOptions = {...defaultOpts, ...options};
       const tf = opts.document.createElement('test-fixture') as TestFixture;
       tf.shouldAttachContents = opts.shouldAttachContents;
       tf.template = template;
 
+
       opts.document.body.appendChild(tf);
+      if (opts.shouldAttachContents) {
+        await tf.updateComplete;
+      }
 
       return tf;
     };