1 files changed, 74 insertions, 0 deletions
diff --git a/spec/frontend/lib/apollo/persist_link_spec.js b/spec/frontend/lib/apollo/persist_link_spec.js
new file mode 100644
index 00000000000..ddb861bcee0
--- /dev/null
+++ b/spec/frontend/lib/apollo/persist_link_spec.js
@@ -0,0 +1,74 @@
+/* eslint-disable no-underscore-dangle */
+import { gql, execute, ApolloLink, Observable } from '@apollo/client/core';
+import { testApolloLink } from 'helpers/test_apollo_link';
+import { getPersistLink } from '~/lib/apollo/persist_link';
+
+const DEFAULT_QUERY = gql`
+  query {
+    foo {
+      bar
+    }
+  }
+`;
+
+const QUERY_WITH_DIRECTIVE = gql`
+  query {
+    foo @persist {
+      bar
+    }
+  }
+`;
+
+const QUERY_WITH_PERSIST_FIELD = gql`
+  query {
+    foo @persist {
+      bar
+      __persist
+    }
+  }
+`;
+
+const terminatingLink = new ApolloLink(() => Observable.of({ data: { foo: { bar: 1 } } }));
+
+describe('~/lib/apollo/persist_link', () => {
+  let subscription;
+
+  afterEach(() => {
+    if (subscription) {
+      subscription.unsubscribe();
+    }
+  });
+
+  it('removes `@persist` directive from the operation', async () => {
+    const operation = await testApolloLink(getPersistLink(), {}, QUERY_WITH_DIRECTIVE);
+    const { selections } = operation.query.definitions[0].selectionSet;
+
+    expect(selections[0].directives).toEqual([]);
+  });
+
+  it('removes `__persist` fields from the operation with `@persist` directive', async () => {
+    const operation = await testApolloLink(getPersistLink(), {}, QUERY_WITH_PERSIST_FIELD);
+
+    const { selections } = operation.query.definitions[0].selectionSet;
+    const childFields = selections[0].selectionSet.selections;
+
+    expect(childFields).toHaveLength(1);
+    expect(childFields.some((field) => field.name.value === '__persist')).toBe(false);
+  });
+
+  it('decorates the response with `__persist: true` is there is `__persist` field in the query', async () => {
+    const link = getPersistLink().concat(terminatingLink);
+
+    subscription = execute(link, { query: QUERY_WITH_PERSIST_FIELD }).subscribe(({ data }) => {
+      expect(data.foo.__persist).toBe(true);
+    });
+  });
+
+  it('does not decorate the response with `__persist: true` is there if query is not persistent', async () => {
+    const link = getPersistLink().concat(terminatingLink);
+
+    subscription = execute(link, { query: DEFAULT_QUERY }).subscribe(({ data }) => {
+      expect(data.foo.__persist).toBe(undefined);
+    });
+  });
+});