implemented tests

test/resolvers/value_resolver_test.dart

@@ -0,0 +1,11 @@
+import 'package:dart_di/resolvers/value_resolver.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test('Value resolver resolves with selected value', () {
+    var a = 3;
+    final valResolver = new ValueResolver(a);
+
+    expect(valResolver.resolve(), a);
+  });
+}