title: How is testify/assert.Contains used with a map?
body: <p>the <a href="https://godoc.org/github.com/stretchr/testify/assert#Contains" rel="noreferrer">docs</a> show this as an example:</p>
  
  <p><code>assert.Contains(t, {"Hello": "World"}, "Hello", "But {'Hello': 'World'} does contain 'Hello'")</code></p>
  
  <p>But running this fails</p>
  
  <pre><code>mymap := map[string]string{}
  mymap["Hello"] = "World"
  assert.Contains(t, mymap, "Hello")
  </code></pre>
  
  <p>results in the error:</p>
  
  <p><code>Error:     "map[Hello:World]" could not be applied builtin len()</code></p>
  
  <p>switching mymap and "hello" results in this:</p>
  
  <p><code>Error:     "Hello" does not contain "map[Hello:World]"</code></p>