Golang Testing — JSON Responses with Gin

Recently I’ve been implementing a small side project in Go with Gin. I know how easy it is to setup tests with Go, but I was very surprised not many people had covered examples of how to test the JSON responses for your APIs. With Gin specifically.

I discovered, it’s quite simple.

First we want an endpoint to test so here we go. The following would return a simple {"hello":"world"} JSON response. On a GET request to / in a file called main.go put:

package main
import (
   "net/http"
   "github.com/gin-gonic/gin"
)
func main() {
   router := SetupRouter()
   router.Run()
}
func SetupRouter() *gin.Engine {
   router := gin.Default()
   router.GET("/", func(c *gin.Context) {
      c.JSON(http.StatusOK, gin.H{
          "hello": "world",
      })
   })
   
   return router
}

Then following conventions with Go we’ll create another file for tests main_test.go in the same directory:

package main
import (
   "encoding/json"
   "net/http"
   "net/http/httptest"
   "testing"
   "github.com/gin-gonic/gin"
   "github.com/stretchr/testify/assert"
)
func performRequest(r http.Handler, method, path string) *httptest.ResponseRecorder {
   req, _ := http.NewRequest(method, path, nil)
   w := httptest.NewRecorder()
   r.ServeHTTP(w, req)
   return w
}
func TestHelloWorld(t *testing.T) {
   // Build our expected body
   body := gin.H{
      "hello": "world",
   }
   // Grab our router
   router := SetupRouter()
   // Perform a GET request with that handler.
   w := performRequest(router, "GET", "/")
   // Assert we encoded correctly,
   // the request gives a 200
   assert.Equal(t, http.StatusOK, w.Code)
   // Convert the JSON response to a map
   var response map[string]string
   err := json.Unmarshal([]byte(w.Body.String()), &response)
   // Grab the value & whether or not it exists
   value, exists := response["hello"]
   // Make some assertions on the correctness of the response.
   assert.Nil(t, err)
   assert.True(t, exists)
   assert.Equal(t, body["hello"], value)
}

Running go test in the same directory as these files will run the tests. I hope this is of use to you, I know it took me a while to find any substantial examples; for now this is the way I’m going to be verifying my JSON responses

Photo by Agence Olloweb on Unsplash

Update: I recently published another article on testing, how to mock Redis, you can check it out here: https://medium.com/@craigchilds94/golang-testing-mocking-redis-b48d09386c70