test(tabs): add more unit tests (#2201)

Author: metonym

tests/Tab/Tab.test.svelte

@@ -0,0 +1,16 @@
+<script lang="ts">
+  import { Tabs, Tab } from "carbon-components-svelte";
+
+  export let label = "Test Tab";
+  export let href = "#test";
+  export let disabled = false;
+  export let tabindex = "0";
+  export let id = "test-tab";
+</script>
+
+<Tabs>
+  <Tab {label} {href} {disabled} {tabindex} {id} />
+  <svelte:fragment slot="content">
+    <div>Test Content</div>
+  </svelte:fragment>
+</Tabs>