test: add test for simple elements streaming

src/__tests__/__snapshots__/stream-elements.expected/step-0.html

@@ -0,0 +1 @@
+<h1>H1</h1>

src/__tests__/__snapshots__/stream-elements.expected/step-1.html

@@ -0,0 +1,2 @@
+<h1>H1</h1>
+<h2>H2</h2>

src/__tests__/__snapshots__/stream-elements.expected/step-2.html

@@ -0,0 +1,3 @@
+<h1>H1</h1>
+<h2>H2</h2>
+<h3>H3</h3>

src/__tests__/index.test.ts

@@ -6,6 +6,8 @@ declare const inlineScriptValues: unknown[];
 
 it("stream-text", fixture(["Hello", "World"]));
 
+it("stream-elements", fixture(["<h1>H1</h1>", "<h2>H2</h2>", "<h3>H3</h3>"]));
+
 it(
   "blocking-scripts",
   fixture([