Test helpers

Learn helpers like t.Helper and t.Cleanup.

Test helpers

Move repeated checks into helper functions and add t.Helper() at the top; then the failure line points to the test line calling the helper, not inside it:

func esit(t *testing.T, got, want int) {
    t.Helper()
    if got != want {
        t.Errorf("got %d, want %d", got, want)
    }
}

For resources needing setup, t.Cleanup(f) registers cleanup to run when the test ends; t.TempDir() gives a temporary folder that is deleted automatically.

Parallel tests and TestMain

Tests that call t.Parallel() run concurrently with the package's other parallel tests, speeding up slow I/O tests. If the whole package needs one-time setup, write TestMain(m *testing.M):

func TestMain(m *testing.M) {
    db := kur()
    kod := m.Run()
    db.Close()
    os.Exit(kod)
}

Exercise Cleanup order

Imitate t.Cleanup's LIFO behavior with defer: inside calistir(), register defer fmt.Println("db kapandı") and then defer fmt.Println("dosya silindi"), then print "test".

Show example solution

package main

import "fmt"

func calistir() {
    defer fmt.Println("db kapandı")
    defer fmt.Println("dosya silindi")
    fmt.Println("test")
}

func main() {
    calistir()
}

Test yourself

In what order do functions registered with <code>t.Cleanup</code> run?
- Randomly
- In parallel
- Last registered runs first (LIFO)
- In registration order
Show answer

Last registered runs first (LIFO) — Cleanup behaves like defer; the resource set up later is closed first.

Fix the line

func esit(t *testing.T, got, want string) {
    t.____()
    if got != want { t.Errorf("got %q, want %q", got, want) }
}

Show answer

func esit(t *testing.T, got, want string) {
    t.Helper()
    if got != want { t.Errorf("got %q, want %q", got, want) }
}

Helper and role

t.Helper()

Correct failure line
t.Cleanup(f)

End-of-test cleanup
t.TempDir()

Temporary folder
t.Parallel()

Concurrent running

Next lesson: Example tests

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies