test: add dom tests

test/dom/index.ts

@@ -0,0 +1,34 @@
+import * as assert from 'assert';
+import { detach } from 'svelte/internal';
+
+describe('dom', () => {
+	describe('detach', () => {
+		describe('when parentNode exists', () => {
+			it('should detach the child from the parent', () => {
+				const parent = document.createElement('div');
+				const child = document.createElement('div');
+				parent.appendChild(child);
+
+				assert.equal(child.parentElement, parent);
+
+				detach(child);
+
+				assert.equal(child.parentElement, null);
+			});
+		});
+		describe('when parentNode does not exist', () => {
+			it('should not throw an exception', () => {
+				const childWithoutParent = document.createElement('div');
+        let error = null;
+
+        try {
+          detach(childWithoutParent);
+        } catch (e) {
+          error = e;
+        }
+
+				assert.equal(error, null);
+			});
+		});
+	});
+});