feature/cache: Add tests for initial cache function

Author: Intellicode

src/cache.spec.js

@@ -0,0 +1,55 @@
+// env jest
+
+const cache = require('./cache');
+
+describe('cache()', () => {
+  const parent = { id: 1 };
+  const args = { name: 'hello' };
+  let cacheMock;
+
+  beforeAll(() => {
+    cacheMock = {
+      get: jest.fn(() => Promise.resolve()),
+    };
+  });
+
+  describe('hashing', () => {
+    it('hashes the root and arguments consistently', () => {
+      const resolver = cache(() => {});
+
+      resolver(parent, args, { resolverCache: cacheMock });
+      resolver(parent, args, { resolverCache: cacheMock });
+
+      const call1Args = cacheMock.get.mock.calls[0][0];
+      const call2Args = cacheMock.get.mock.calls[1][0];
+
+      expect(call1Args).toEqual(call2Args);
+    });
+  });
+
+  describe('cache retrieval', () => {
+    const cachedValue = 'cached';
+    const uncachedValue = 'uncached';
+    const resolver = cache(() => uncachedValue);
+
+    it('returns cached value if the cache returns a value', () => {
+      cacheMock.get = jest.fn(() => Promise.resolve(cachedValue));
+
+      expect.assertions(1);
+
+      resolver(parent, args, { resolverCache: cacheMock }).then(actual => {
+        expect(actual).toEqual(cachedValue);
+      });
+    });
+
+    it('returns uncached value if the cache returns undefined', () => {
+      cacheMock.get = jest.fn(() => Promise.resolve(undefined));
+
+      expect.assertions(1);
+
+      resolver(parent, args, { resolverCache: cacheMock }).then(actual => {
+        expect(actual).toEqual(uncachedValue);
+      });
+    });
+  });
+});