1 files changed, 49 insertions, 0 deletions
diff --git a/spec/frontend/__helpers__/fake_date.js b/spec/frontend/__helpers__/fake_date.js
new file mode 100644
index 00000000000..5391ae04797
--- /dev/null
+++ b/spec/frontend/__helpers__/fake_date.js
@@ -0,0 +1,49 @@
+// Frida Kahlo's birthday (6 = July)
+export const DEFAULT_ARGS = [2020, 6, 6];
+
+const RealDate = Date;
+
+const isMocked = (val) => Boolean(val.mock);
+
+export const createFakeDateClass = (ctorDefault) => {
+  const FakeDate = new Proxy(RealDate, {
+    construct: (target, argArray) => {
+      const ctorArgs = argArray.length ? argArray : ctorDefault;
+
+      return new RealDate(...ctorArgs);
+    },
+    apply: (target, thisArg, argArray) => {
+      const ctorArgs = argArray.length ? argArray : ctorDefault;
+
+      return new RealDate(...ctorArgs).toString();
+    },
+    // We want to overwrite the default 'now', but only if it's not already mocked
+    get: (target, prop) => {
+      if (prop === 'now' && !isMocked(target[prop])) {
+        return () => new RealDate(...ctorDefault).getTime();
+      }
+
+      return target[prop];
+    },
+    getPrototypeOf: (target) => {
+      return target.prototype;
+    },
+    // We need to be able to set props so that `jest.spyOn` will work.
+    set: (target, prop, value) => {
+      // eslint-disable-next-line no-param-reassign
+      target[prop] = value;
+      return true;
+    },
+  });
+
+  return FakeDate;
+};
+
+export const useFakeDate = (...args) => {
+  const FakeDate = createFakeDateClass(args.length ? args : DEFAULT_ARGS);
+  global.Date = FakeDate;
+};
+
+export const useRealDate = () => {
+  global.Date = RealDate;
+};