Piye carane ngetèst kode Go?

Question

Accepted Answer

Go nduweni **testing built-in** liwat paket `testing` lan perintah `go test` — ora perlu framework eksternal. Tests manggon ing file `_test.go`, lan Go ngutamakake **table-driven tests**, benchmarks, lan tooling sing apik minangka fitur first-class.

## A basic test

```go
// math.go
func Add(a, b int) int { return a + b }

// math_test.go — same package, _test.go suffix
import "testing"

func TestAdd(t *testing.T) {     // Test prefix + *testing.T parameter
    result := Add(2, 3)
    if result != 5 {
        t.Errorf("Add(2,3) = %d; want 5", result)   // report failure (continues)
        // t.Fatalf stops the test immediately
    }
}
// run with: go test  (or `go test -v` for verbose, `go test ./...` for all packages)
```

Fungsi test diwiwiti karo `Test`, njupuk `*testing.T`, lan nglaporake kegagalan liwat `t.Errorf`/`t.Fatalf`. Ora ana keyword assertion — sampeyan mriksa kondisi karo `if` biasa lan nglaporake kegagalan (Go luwih seneng gaya sing eksplisit iki).

## Table-driven tests — pola idiomatic Go

```go
func TestAdd(t *testing.T) {
    tests := []struct {           // a table of test CASES
        name     string
        a, b     int
        expected int
    }{
        {"positives", 2, 3, 5},
        {"with zero", 0, 5, 5},
        {"negatives", -1, -1, -2},
    }
    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {     // a SUBTEST per case (named, isolated)
            if got := Add(tt.a, tt.b); got != tt.expected {
                t.Errorf("Add(%d,%d) = %d; want %d", tt.a, tt.b, got, tt.expected)
            }
        })
    }
}
```

**Table-driven tests** minangka idiom Go sing dominan — nggawe slice kasus, loop over karo `t.Run` subtests. Iki nggawe nambah kasus jadi gampang lan menehi reporting pass/fail sing jelas lan individual per kasus.

## Benchmarks — testing performa built-in

```go
func BenchmarkAdd(b *testing.B) {
    for i := 0; i < b.N; i++ {     // the framework chooses b.N for statistical accuracy
        Add(2, 3)
    }
}
// go test -bench=. → reports ns/op (and -benchmem for allocations)
```

## Coverage lan tooling liyane

```bash
go test -cover                    # coverage percentage
go test -coverprofile=c.out       # then: go tool cover -html=c.out (visual report)
go test -race                     # the RACE DETECTOR — finds data races (crucial for concurrency)
go test -run TestAdd              # run specific tests
```

Flag **`-race`** arang penting — ndeteksi data races ing kode concurrent, alat kunci amarga fokus concurrency Go.

## Test helpers lan setup

```go
func TestMain(m *testing.M) {     // package-level setup/teardown
    setup()
    code := m.Run()
    teardown()
    os.Exit(code)
}
// t.Helper() marks a function as a test helper (better failure line reporting)
// httptest package for testing HTTP handlers; interfaces for mocking dependencies
```

## Mengapa penting

Testing minangka bagian first-class, built-in Go — paket `testing` lan `go test` ora mbutuhake framework eksternal, ngrefleksikake enfase Go ing testing minangka praktik inti.

Nembe konvensi iku essential everyday knowledge: file `_test.go` lan struktur `TestXxx(t *testing.T)`, gaya failure-reporting sing eksplisit (tanpa assertion), lan utamané pola **table-driven test** sing dominan idiomatic Go (nyakup akeh kasus kanthi compact karo reporting per-kasus sing jelas liwat subtests).

Tuduh penting uga **benchmarks** Go built-in (performa minangka testable concern) lan **tooling** sing kuat — analisis coverage lan utamané **detector `-race`**, sing nemokake data races ing kode concurrent (vital amarga panggunaan concurrency-heavy Go).

Nembe carane nulis tests effective lan idiomatic Go, gunakaké race detector, lan leverage `httptest`/interfaces kanggo ngetèst komponen nyata minangka hallmark professional Go development lan topik sing asring ngrefleksikake code-quality fluency.