Go Test function

main.go

…

Expected output

Lesson notes

Test function

Learn the func TestXxx signature and the go test command.

Test functions

In Go, tests are written in files ending with _test.go and run with go test. A test function starts with Test and takes a *testing.T:

// topla_test.go
package hesap

import "testing"

func TestTopla(t *testing.T) {
    if got := Topla(2, 3); got != 5 {
        t.Errorf("Topla(2, 3) = %d, beklenen 5", got)
    }
}

There is no separate test framework; the standard testing package is enough.

go test flags

Commonly used flags:

go test ./...            # all packages
go test -v -run TestTopla # verbose, tests matching the name
go test -race ./...      # data race detection
go test -cover ./...     # coverage
go test -count=1 ./...   # skip the cache

Tests can access the package's internal functions; to look from outside, use package hesap_test.

Exercise Mini test runner

Imitate the essence of a test: write Topla(a, b int) int. In main, compute got := Topla(2, 3) and print "FAIL" if got != 5, otherwise "PASS".

Show example solution

package main

import "fmt"

func Topla(a, b int) int { return a + b }

func main() {
    if got := Topla(2, 3); got != 5 {
        fmt.Println("FAIL")
        return
    }
    fmt.Println("PASS")
}

Test yourself

Which function does <code>go test</code> run as a test?
- func TestToplam()
- func TestToplam(t *testing.T)
- func testToplam(t *testing.T)
- func Testtoplam(t *testing.T)
Show answer

func TestToplam(t *testing.T) — The name must start with Test followed by an upper-case letter (or nothing), and the only parameter must be *testing.T.

Test file

// topla____.go
package hesap

Show answer

// topla_test.go
package hesap

Flag and effect

-v

Verbose output
-run

Filter by name
-race

Race detection
-cover

Coverage

Next lesson: t.Error and t.Fatal