1 files changed, 63 insertions, 0 deletions
diff --git a/spec/frontend/vue_shared/new_namespace/components/legacy_container_spec.js b/spec/frontend/vue_shared/new_namespace/components/legacy_container_spec.js
new file mode 100644
index 00000000000..52f36aa0e77
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+++ b/spec/frontend/vue_shared/new_namespace/components/legacy_container_spec.js
@@ -0,0 +1,63 @@
+import { shallowMount } from '@vue/test-utils';
+import { setHTMLFixture, resetHTMLFixture } from 'helpers/fixtures';
+import LegacyContainer from '~/vue_shared/new_namespace/components/legacy_container.vue';
+
+describe('Legacy container component', () => {
+  let wrapper;
+  let dummy;
+
+  const createComponent = (propsData) => {
+    wrapper = shallowMount(LegacyContainer, { propsData });
+  };
+
+  afterEach(() => {
+    wrapper.destroy();
+    resetHTMLFixture();
+    wrapper = null;
+  });
+
+  describe('when selector targets real node', () => {
+    beforeEach(() => {
+      setHTMLFixture('<div class="dummy-target"></div>');
+      dummy = document.querySelector('.dummy-target');
+      createComponent({ selector: '.dummy-target' });
+    });
+
+    describe('when mounted', () => {
+      it('moves node inside component', () => {
+        expect(dummy.parentNode).toBe(wrapper.element);
+      });
+
+      it('sets active class', () => {
+        expect(dummy.classList.contains('active')).toBe(true);
+      });
+    });
+
+    describe('when unmounted', () => {
+      beforeEach(() => {
+        wrapper.destroy();
+      });
+
+      it('moves node back', () => {
+        expect(dummy.parentNode).toBe(document.body);
+      });
+
+      it('removes active class', () => {
+        expect(dummy.classList.contains('active')).toBe(false);
+      });
+    });
+  });
+
+  describe('when selector targets template node', () => {
+    beforeEach(() => {
+      setHTMLFixture('<template class="dummy-target">content</template>');
+      dummy = document.querySelector('.dummy-target');
+      createComponent({ selector: '.dummy-target' });
+    });
+
+    it('copies node content when mounted', () => {
+      expect(dummy.innerHTML).toEqual(wrapper.element.innerHTML);
+      expect(dummy.parentNode).toBe(document.body);
+    });
+  });
+});