Add (minimal) test

See issue #31

packages/provider/test/unit.js

+import {assert} from 'chai';
+
+import '../src/dbp-provider';
+import '../src/dbp-provider-demo';
+
+suite('dbp-provider basics', () => {
+    let node;
+
+    suiteSetup(async () => {
+        node = document.createElement('dbp-provider');
+        document.body.appendChild(node);
+        await node.updateComplete;
+    });
+
+    suiteTeardown(() => {
+        node.remove();
+    });
+
+    test('should render', () => {
+        assert(node.shadowRoot !== undefined);
+    });
+});
+
+suite('dbp-provider-demo basics', () => {
+    let node;
+
+    suiteSetup(async () => {
+        node = document.createElement('dbp-provider-demo');
+        document.body.appendChild(node);
+        await node.updateComplete;
+    });
+
+    suiteTeardown(() => {
+        node.remove();
+    });
+
+    test('should render', () => {
+        assert(node.shadowRoot !== undefined);
+    });
+});