golang: Separating Integration Tests and Unit Tests

_.md

Separating Integration Tests and Unit Tests

We can use build tags to run only certain types of tests. In this case, we want integration tests to run by default, so we tag the integration tests with a negated unit test tag, which indicates that the test should not be run if the unit build flag is set.

Alternatively, the integration tests could be tagged with integration or some other tag, and they'd only be run if the integration tag is set on test invocation.

How to run go test with tags

$ go test -tags unit

foo.go

package foo

import "io"

type Foo struct{}

func (f Foo) String() string {
	return "foo"
}

// Read is not properly implemented since it just returns EOF no matter what,
// even if the destination buffer is not large enough to contain the entire
// "foo" string, but for this example's purposes, it's fine. Do as I say, not
// as I do: don't actually write a reader like this. :O
func (f Foo) Read(b []byte) (int, error) {
	s := []byte(f.String())
	l := len(s)
	if len(b) < l {
		l = len(b)
	}
	return copy(b, s[:l]), io.EOF
}

foo_integration_test.go

// +build !unit

package foo

import (
	"bytes"
	"io"
	"testing"
)

func TestRead(t *testing.T) {
	f := Foo{}
	w := &bytes.Buffer{}
	io.Copy(w, f)
	if w.String() != "foo" {
		t.Error("expected 'foo'")
	}
}

foo_test.go

package foo

import "testing"

func TestFoo(t *testing.T) {
	f := Foo{}
	if f.String() != "foo" {
		t.Error("expected 'foo'")
	}
}

zTestRun: All

$ go test -v
=== RUN   TestRead
--- PASS: TestRead (0.00s)
=== RUN   TestFoo
--- PASS: TestFoo (0.00s)
PASS
ok  	_/tmp/test_test	0.006s

zTestRun: Unit Tests Only

$ go test -v -tags unit
=== RUN   TestFoo
--- PASS: TestFoo (0.00s)
PASS
ok  	_/tmp/test_test	0.006s