Make mock gin.Context in Golang

In order to get a *gin.Context instance that you can test, you need a mock HTTP request and response. An easy way to create those is to use the net/http and net/http/httptest packages. Based on the code you linked, your test would look like this:

package main

import (
    "net/http"
    "net/http/httptest"
    "testing"

    "github.com/gin-gonic/gin"
)

func TestControllerGetAll(t *testing.T) {

    // Switch to test mode so you don't get such noisy output
    gin.SetMode(gin.TestMode)

    // Setup your router, just like you did in your main function, and
    // register your routes
    r := gin.Default()
    r.GET("/users", GetUsers)

    // Create the mock request you'd like to test. Make sure the second argument
    // here is the same as one of the routes you defined in the router setup
    // block!
    req, err := http.NewRequest(http.MethodGet, "/users", nil)
    if err != nil {
        t.Fatalf("Couldn't create request: %v\n", err)
    }

    // Create a response recorder so you can inspect the response
    w := httptest.NewRecorder()

    // Perform the request
    r.ServeHTTP(w, req)

    // Check to see if the response was what you expected
    if w.Code != http.StatusOK {
        t.Fatalf("Expected to get status %d but instead got %d\n", http.StatusOK, w.Code)
    }
}

Although you could create a mock *gin.Context, it's probably easier to use the method above, since it'll execute and handle your request the same as it would an actual request.

Gin provides the option to create a Test Context which you can use for whatever you need: https://godoc.org/github.com/gin-gonic/gin#CreateTestContext

Like that:

c, _ := gin.CreateTestContext(httptest.NewRecorder())

Here is an example of how I mock a context, add a param, use it in a function, then print the string of the response if there was a non-200 response.

gin.SetMode(gin.TestMode)

w := httptest.NewRecorder()
c, _ := gin.CreateTestContext(w)

c.Params = []gin.Param{gin.Param{Key: "k", Value: "v"}}

foo(c)

if w.Code != 200 {
    b, _ := ioutil.ReadAll(w.Body)
    t.Error(w.Code, string(b))
}