Create an abstract class for tests

Created test.dart containing a class named Test.

Author: thomasio101

common/test.dart

@@ -0,0 +1,9 @@
+import 'data.dart';
+
+typedef num Workload<T>(T);
+
+abstract class Test<T> {
+  Workload<T> workload;
+
+  num call(Iterable<T> dataPoint);
+}