code: function checkResponse(actual, expected, bindings) {
  
      debug('Checking response, expecting:', expected)
  
      addTest('Status: ' + expected.title, function() {
        assert.equal(actual.statusCode, expected.code)
      })
  
      for (var key in expected.headers) {
        var val = expected.headers[key]
        addTest('Header: ' + key + ': ' + val, function() {
          assert.ok(actual.headers[key], "Header " + key + " expected, but not found")
          assert.ok(interpolate.match(actual.headers[key], val, bindings), "Expected headers to match")
        })
      }
  
      if (expected.body) {
        assertBodyMatches(actual.body, expected.body, bindings)
      } else {
        addTest('No body', function() {
          if (actual.body) assert.fail(actual.body, '', "Expected empty body")
        })
      }
    }
docs: Internal: interpolate the values from `context` into the `params` struct