Unit testing http json response in Golang

I am using gin as my http server and sending back an empty array in json as my response:

c.JSON(http.StatusOK, []string{})

The resulting json string I get is "[]\n". The newline is added by the json Encoder object, see here.

Using goconvey, I could test my json like

So(response.Body.String(), ShouldEqual, "[]\n")

But is there a better way to generate the expected json string than just adding a newline to all of them?

You should first unmarshal the body of the response into a struct and compare against the resulting object. Example:

result := []string{}
if err := json.NewDecoder(response.Body).Decode(&result); err != nil {
    log.Fatalln(err)
}
So(len(result), ShouldEqual, 0)

Unmarshal the body into a struct and the use Gocheck's DeepEquals
https://godoc.org/launchpad.net/gocheck

You may find jsonassert useful.
It has no dependencies outside the standard library and allows you to verify that JSON strings are semantically equivalent to a JSON string you expect.

In your case:

// white space is ignored, no need for \n
jsonassert.New(t).Assertf(response.Body().String(), "[]")

It can handle any form of JSON, and has very friendly assertion error messages.

Disclaimer: I wrote this package.

I made it this way. Because I don't want to include an extra library.

tc := testCase{
    w: httptest.NewRecorder(),
    wantResponse: mustJson(t, map[string]string{"message": "unauthorized"}),
}
...

if tc.wantResponse != tc.w.Body.String() {
	t.Errorf("want %s, got %s", tt.wantResponse, tt.w.Body.String())
}

...
func mustJson(t *testing.T, v interface{}) string {
	t.Helper()
	out, err := json.Marshal(v)
	if err != nil {
		t.Fatal(err)
	}
	return string(out)
}