How to unit testing with Gorm, mux, postgresql - rest

Question

I'm new in Go and unit test. I build a samll side projecy called "urlshortener" using Go with Gorm, mux and postgresql.
There is a qeustion annoying me after search many articles.
To make the question clean, I delete some irrelevant code like connect db, .env, etc
My code is below(main.go):
package main
type Url struct {
ID uint `gorm:"primaryKey"` // used for shortUrl index
Url string `gorm:"unique"` // prevent duplicate url
ExpireAt string
ShortUrl string
}
var db *gorm.DB
var err error
func main() {
// gain access to database by getting .env
...
// database connection string
...
// make migrations to the dbif they have not already been created
db.AutoMigrate(&Url{})
// API routes
router := mux.NewRouter()
router.HandleFunc("/{id}", getURL).Methods("GET")
router.HandleFunc("/api/v1/urls", createURL).Methods("POST")
router.HandleFunc("/create/urls", createURLs).Methods("POST")
// Listener
http.ListenAndServe(":80", router)
// close connection to db when main func finishes
defer db.Close()
}
Now I'm building unit test for getURL function, which is a GET method to get data from my postgresql database called urlshortener and the table name is urls.
Here is getURL function code:
func getURL(w http.ResponseWriter, r *http.Request) {
params := mux.Vars(r)
var url Url
err := db.Find(&url, params["id"]).Error
if err != nil {
w.WriteHeader(http.StatusNotFound)
} else {
w.WriteHeader(http.StatusOK)
json.NewEncoder(w).Encode(url.Url)
}
}
This is work fine with my database. See curl command below:
I know that the unit test is not for mock data, and it aim to test a function/method is stable or not. Although I import mux and net/http for conncetion, but I think the unit test on it should be "SQL syntax". So I decide to focus on testing if gorm return the right value to the test function.
In this case, db.Find will return a *gorm.DB struct which should be exactly same with second line. (see docs https://gorm.io/docs/query.html)
db.Find(&url, params["id"])
SELECT * FROM urls WHICH id=<input_number>
My question is how to write a unit test on it for check the SQL syntax is correct or not in this case (gorm+mux)? I've check some articles, but most of them are testing the http connect status but not for SQL.
And my function do not have the return value, or I need to rewrite the function to have a return value before I can test it?
below is the test structure in my mind:
func TestGetURL(t *testing.T) {
//set const answer for this test
//set up the mock sql connection
//call getURL()
//check if equal with answer using assert
}
Update
According to #Emin Laletovic answer
Now I have a prototype of my testGetURL. Now I have new questions on it.
func TestGetURL(t *testing.T) {
//set const answer for this test
testQuery := `SELECT * FROM "urls" WHERE id=1`
id := 1
//set up the mock sql connection
testDB, mock, err := sqlmock.New()
if err != nil {
panic("sqlmock.New() occurs an error")
}
// uses "gorm.io/driver/postgres" library
dialector := postgres.New(postgres.Config{
DSN: "sqlmock_db_0",
DriverName: "postgres",
Conn: testDB,
PreferSimpleProtocol: true,
})
db, err = gorm.Open(dialector, &gorm.Config{})
if err != nil {
panic("Cannot open stub database")
}
//mock the db.Find function
rows := sqlmock.NewRows([]string{"id", "url", "expire_at", "short_url"}).
AddRow(1, "http://somelongurl.com", "some_date", "http://shorturl.com")
mock.ExpectQuery(regexp.QuoteMeta(testQuery)).
WillReturnRows(rows).WithArgs(id)
//create response writer and request for testing
mockedRequest, _ := http.NewRequest("GET", "/1", nil)
mockedWriter := httptest.NewRecorder()
//call getURL()
getURL(mockedWriter, mockedRequest)
//check values in mockedWriter using assert
}
In the code, I mock the request and respone with http, httptest libs.
I run the test, but it seems that the getURL function in main.go cannot receive the args I pass in, see the pic below.
when db.find called, mock.ExpectQuery receive it and start to compare it, so far so good.
db.Find(&url, params["id"])
mock.ExpectQuery(regexp.QuoteMeta(testQuery)).WillReturnRows(rows).WithArgs(id)
According to the testing log, it shows that when db.Find triggerd, it only excute SELECT * FROM "urls" but not I expected SELECT * FROM "urls" WHERE "urls"."id" = $1.
But when I test db.Find on local with postman and log the SQL syntax out, it can be excute properly. see pic below.
In summary, I think the problem is the responeWriter/request I put in getURL(mockedWriter, mockedRequest) are wrong, and it leads that getURL(w http.ResponseWriter, r *http.Request) cannot work as we expect.
Please let me know if I missing anything~
Any idea or way to rewrite the code would be help, thank you!

Answer 1

If you just want to test the SQL string that db.Find returns, you can use the DryRun feature (per documentation).
stmt := db.Session(&Session{DryRun: true}).Find(&url, params["id"]).Statement
stmt.SQL.String() //returns SQL query string without the param value
stmt.Vars // contains an array of input params
However, to write a test for the getURL function, you could use sqlmock to mock the results that would be returned when executing the db.Find call.
func TestGetURL(t *testing.T) {
//set const answer for this test
testQuery := "SELECT * FROM `urls` WHERE `id` = $1"
id := 1
//create response writer and request for testing
//set up the mock sql connection
testDB, mock, err := sqlmock.New()
//handle error
// uses "gorm.io/driver/postgres" library
dialector := postgres.New(postgres.Config{
DSN: "sqlmock_db_0",
DriverName: "postgres",
Conn: testDB,
PreferSimpleProtocol: true,
})
db, err = gorm.Open(dialector, &gorm.Config{})
//handle error
//mock the db.Find function
rows := sqlmock.NewRows([]string{"id", "url", "expire_at", "short_url"}).
AddRow(1, "http://somelongurl.com", "some_date", "http://shorturl.com")
mock.ExpectQuery(regexp.QuoteMeta(testQuery)).
WillReturnRows(rows).WithArgs(id)
//call getURL()
getUrl(mockedWriter, &mockedRequest)
//check values in mockedWriter using assert
}

Answer 2

This Post and Emin Laletovic are really helps me alot.
I think I get the answer to this qeustion.
Let's recap this questioon. First, I'm using gorm for postgresql and mux for http services and build a CRUD service.
I need to write a unit test to check if my database syntax is correct (we assuming that the connection is statusOK), so we focus on how to write a unit test for SQL syntax.
But the handler function in main.go don't have return value, so we need to use mock-sql/ ExpectQuery(), this function will be triggered when the db.Find() inside getURL(). By doing this, we dont have to return a value to check if it match our target or not.
The problem I met in Update is fixed by This Post, building an unit test with mux, but that post is focusing on status check and return value.
I set the const answer for this test, the id variable is what we expect to get. Noticed that $1 I don't know how to change it, and I've try many times to rewrite but SQL syntax is still return $1, maybe it is some kind of constraint I dont know.
//set const answer for this test
testQuery := `SELECT * FROM "urls" WHERE "urls"."id" = $1`
id := "1"
I set the value pass into the getURL() by doint this
//set the value send into the function
vars := map[string]string{
"id": "1",
}
//create response writer and request for testing
mockedWriter := httptest.NewRecorder()
mockedRequest := httptest.NewRequest("GET", "/{id}", nil)
mockedRequest = mux.SetURLVars(mockedRequest, vars)
Finally, we call mock.ExpectationsWereMet() to check if anything went wrong.
if err := mock.ExpectationsWereMet(); err != nil {
t.Errorf("SQL syntax is not match: %s", err)
}
Below is my test code:
func TestGetURL(t *testing.T) {
//set const answer for this test
testQuery := `SELECT * FROM "urls" WHERE "urls"."id" = $1`
id := "1"
//set up the mock sql connection
testDB, mock, err := sqlmock.New()
if err != nil {
panic("sqlmock.New() occurs an error")
}
// uses "gorm.io/driver/postgres" library
dialector := postgres.New(postgres.Config{
DSN: "sqlmock_db_0",
DriverName: "postgres",
Conn: testDB,
PreferSimpleProtocol: true,
})
db, err = gorm.Open(dialector, &gorm.Config{})
if err != nil {
panic("Cannot open stub database")
}
//mock the db.Find function
rows := sqlmock.NewRows([]string{"id", "url", "expire_at", "short_url"}).
AddRow(1, "url", "date", "shorurl")
//try to match the real SQL syntax we get and testQuery
mock.ExpectQuery(regexp.QuoteMeta(testQuery)).WillReturnRows(rows).WithArgs(id)
//set the value send into the function
vars := map[string]string{
"id": "1",
}
//create response writer and request for testing
mockedWriter := httptest.NewRecorder()
mockedRequest := httptest.NewRequest("GET", "/{id}", nil)
mockedRequest = mux.SetURLVars(mockedRequest, vars)
//call getURL()
getURL(mockedWriter, mockedRequest)
//check result in mockedWriter mocksql built function
if err := mock.ExpectationsWereMet(); err != nil {
t.Errorf("SQL syntax is not match: %s", err)
}
}
And I run two tests with args(1, 1) and args(1, 2), and it works fine. see pic below(please ignore the chinese words)