title: Manual mock not working in with Jest
body: <p>Can somebody help me with manual mocking in Jest, please? :)
  I try to have Jest use the mock instead of the actual module.</p>
  
  <p>my test: </p>
  
  <pre><code>// __tests__/mockTest.js
  
  import ModuleA from "../src/ModuleA"
  
  describe("ModuleA", () =&gt; {
      beforeEach(() =&gt; {
          jest.mock("../src/ModuleA")
      })
  
      it("should return the mock name", () =&gt; {
          const name = ModuleA.getModuleName()
          expect(name).toBe("mockModuleA")
      })
  })
  </code></pre>
  
  <p>my code:</p>
  
  <pre><code>// src/ModuleA.js
  export default {
      getModuleName: () =&gt; "moduleA"
  }
  
  // src/__mocks__/ModuleA.js
  export default {
      getModuleName: () =&gt; "mockModuleA"
  }
  </code></pre>
  
  <p>I think I followed everything the <a href="https://facebook.github.io/jest/docs/en/manual-mocks.html" rel="noreferrer">documentation</a> says about manual mocks, but perhaps I'm overlooking something here?
  This is my result:</p>
  
  <pre><code>Expected value to be:
        "mockModuleA"
  Received:
        "moduleA"
  </code></pre>