Testing QueryStrings in http.Request

Posted on Sat 14 November 2015

This one threw me; say you have a subject that reads a value from an HTTP Request's Query, something like this:

func ValidateState(req *http.Request) error {
    fwdState := req.URL.Query().Get("state")
    if fwdState !== "expected" {
      return fmt.Errorf("Unexpected state value: %s", fwdState)
    }
    return nil
}

In order to test this method, you'll want to create an http.Request instead and pre-populate the QueryString. My first attempt was the reverse how we read the Query value:

func Test_ValidateState(t *testing.T) {
    req := &http.Request{URL:&url.URL{}}
    req.URL.Query().Set("state", "expected")
    err := ValidateState(req)
    require.NoError(t, err)
}

However, this fails with the ValidateState function returning an "Unexepcted state value: " error. Instead, we need to set the Request.URL.RawQuery value directly:

func Test_ValidateState(t *testing.T) {
    req := &http.Request{URL:&url.URL{}}
    req.URL.RawQuery = "state=expected"
    err := ValidateState(req)
    require.NoError(t, err)
}