1 files changed, 54 insertions, 0 deletions
diff --git a/spec/frontend/lib/apollo/instrumentation_link_spec.js b/spec/frontend/lib/apollo/instrumentation_link_spec.js
new file mode 100644
index 00000000000..ef686129257
--- /dev/null
+++ b/spec/frontend/lib/apollo/instrumentation_link_spec.js
@@ -0,0 +1,54 @@
+import { testApolloLink } from 'helpers/test_apollo_link';
+import { getInstrumentationLink, FEATURE_CATEGORY_HEADER } from '~/lib/apollo/instrumentation_link';
+
+const TEST_FEATURE_CATEGORY = 'foo_feature';
+
+describe('~/lib/apollo/instrumentation_link', () => {
+  const setFeatureCategory = (val) => {
+    window.gon.feature_category = val;
+  };
+
+  afterEach(() => {
+    getInstrumentationLink.cache.clear();
+  });
+
+  describe('getInstrumentationLink', () => {
+    describe('with no gon.feature_category', () => {
+      beforeEach(() => {
+        setFeatureCategory(null);
+      });
+
+      it('returns null', () => {
+        expect(getInstrumentationLink()).toBe(null);
+      });
+    });
+
+    describe('with gon.feature_category', () => {
+      beforeEach(() => {
+        setFeatureCategory(TEST_FEATURE_CATEGORY);
+      });
+
+      it('returns memoized apollo link', () => {
+        const result = getInstrumentationLink();
+
+        // expect.any(ApolloLink) doesn't work for some reason...
+        expect(result).toHaveProp('request');
+        expect(result).toBe(getInstrumentationLink());
+      });
+
+      it('adds a feature category header from the returned apollo link', async () => {
+        const defaultHeaders = { Authorization: 'foo' };
+        const operation = await testApolloLink(getInstrumentationLink(), {
+          context: { headers: defaultHeaders },
+        });
+
+        const { headers } = operation.getContext();
+
+        expect(headers).toEqual({
+          ...defaultHeaders,
+          [FEATURE_CATEGORY_HEADER]: TEST_FEATURE_CATEGORY,
+        });
+      });
+    });
+  });
+});