title: How to test if an array contains arrays? (Jest)
body: <p>Given the following function:</p>
  
  <pre><code>chunk = (arr, n) =&gt; {
      return arr.reduce(function(p, cur, i) {
          (p[i/n|0] = p[i/n|0] || []).push(cur);
          return p;
      }, []);
  }
  </code></pre>
  
  <p>I want to test if the output array contains arrays:</p>
  
  <pre><code>test("Splits a given array in N arrays", () =&gt; {
      let _input = Array.from({length: 999}, () =&gt; Math.floor(Math.random() * 999));;
      let int = mockService.getRandomArbitrary();
      expect(generalService.chunk(_input, int)).toContain(???????);
  })
  </code></pre>
  
  <p>Considering <a href="https://jestjs.io/docs/en/using-matchers#arrays-and-iterables" rel="nofollow noreferrer">matchers</a>, how can one test if an array contains arrays?</p>