Introduction
In this example, I will create unit tests using the httptest library and we will see how to create test coverage for http handlers.
How to test http handlers in Go?
So we can test any handler http, we need a structure to be able to store the handler response, such as http status code, headers, body, etc.
The package httptest provide the structure httptest.ResponseRecorder, that's all we need to store the handler response.
// NewRecorder returns an initialized ResponseRecorder.
func NewRecorder() *ResponseRecorder {
return &ResponseRecorder{
HeaderMap: make(http.Header),
Body: new(bytes.Buffer),
Code: 200,
}
}
The sample API
In our sample API, we have a handler called /check-is-prime, which checks if a number is prime.
The code:
The first test
The logic of the tests is very simple, for each test we build the HTTP request and then compare the response.
Adding more tests
Using table design in tests, its easy to add more cases:
{
name: "must return http.StatusOk and true to prime number (7)",
args: func(*testing.T) args {
req, err := http.NewRequest("GET", "/check-is-prime", nil)
if err != nil {
t.Fatalf("fail to create request: %s", err.Error())
}
q := req.URL.Query()
q.Add("number", "7")
req.URL.RawQuery = q.Encode()
return args{
req: req,
}
},
wantCode: http.StatusOK,
wantBody: "true",
},
{
name: "must return http.StatusOk and false because number (1) is not prime",
args: func(*testing.T) args {
req, err := http.NewRequest("GET", "/check-is-prime", nil)
if err != nil {
t.Fatalf("fail to create request: %s", err.Error())
}
q := req.URL.Query()
q.Add("number", "1")
req.URL.RawQuery = q.Encode()
return args{
req: req,
}
},
wantCode: http.StatusOK,
wantBody: "false",
},
Complete code:
Conclusion
Have these utilities in the Go standard library, helps a lot when creating and maintaining our tests. We saw in practice with the package httptest.
Another important point is to isolate mux creation, this is necessary to call handlers in tests.
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