Testing in Go: The `testing` Package

Testing in Go: The testing Package

Testing is built into Go. This lesson explains how to write unit tests, run them, and use table-driven patterns.

Unit testing

Create a file ending in _test.go and use the testing package.

package main

import "testing"

func TestAdd(t *testing.T) {
    got := add(2, 3)
    want := 5
    if got != want {
        t.Fatalf("add(2,3) = %d; want %d", got, want)
    }
}

Run tests with:

go test ./... -v

Table-driven tests

Use a slice of cases to test many inputs with the same logic.

func TestIsEven(t *testing.T) {
    cases := []struct{ in int; want bool }{{2,true},{3,false},{0,true}}
    for _, c := range cases {
        if got := isEven(c.in); got != c.want {
            t.Errorf("isEven(%d) = %v; want %v", c.in, got, c.want)
        }
    }
}

Benchmarks

Benchmark code measures performance and runs repeatedly.

func BenchmarkAdd(b *testing.B) {
    for i := 0; i < b.N; i++ {
        add(i, i)
    }
}