Add failing test for null hydration

test/hydration/samples/dynamic-text-nil/_after.html

@@ -0,0 +1,2 @@
+<p></p>
+<p>undefined</p>

test/hydration/samples/dynamic-text-nil/_before.html

@@ -0,0 +1,2 @@
+<p>null</p>
+<p>undefined</p>

test/hydration/samples/dynamic-text-nil/_config.js

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+export default {
+	props: {},
+
+	snapshot(target) {
+		const nullText = target.querySelectorAll('p')[0].textContent;
+		const undefinedText = target.querySelectorAll('p')[1].textContent;
+
+		return {
+			nullText,
+			undefinedText,
+		};
+	},
+
+	test(assert, target, snapshot) {
+		const nullText = target.querySelectorAll('p')[0].textContent;
+		const undefinedText = target.querySelectorAll('p')[1].textContent;
+
+		assert.equal(nullText, snapshot.nullText);
+		assert.equal(undefinedText, snapshot.undefinedText);
+	},
+};

test/hydration/samples/dynamic-text-nil/main.svelte

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+<script>
+	let maybeNull = null;
+	let maybeUndefined = undefined;
+</script>
+
+<p>{maybeNull}</p>
+<p>{maybeUndefined}</p>