moby/pkg/libcontainer/cgroups/fs/test_util.go

/*
Utility for testing cgroup operations.

Creates a mock of the cgroup filesystem for the duration of the test.
*/
package fs

import (
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"testing"
)

type cgroupTestUtil struct {
	// data to use in tests.
	CgroupData *data

	// Path to the mock cgroup directory.
	CgroupPath string

	// Temporary directory to store mock cgroup filesystem.
	tempDir string
	t       *testing.T
}

// Creates a new test util for the specified subsystem
func NewCgroupTestUtil(subsystem string, t *testing.T) *cgroupTestUtil {
	d := &data{}
	tempDir, err := ioutil.TempDir("", fmt.Sprintf("%s_cgroup_test", subsystem))
	if err != nil {
		t.Fatal(err)
	}
	d.root = tempDir
	testCgroupPath, err := d.path(subsystem)
	if err != nil {
		t.Fatal(err)
	}

	// Ensure the full mock cgroup path exists.
	err = os.MkdirAll(testCgroupPath, 0755)
	if err != nil {
		t.Fatal(err)
	}
	return &cgroupTestUtil{CgroupData: d, CgroupPath: testCgroupPath, tempDir: tempDir, t: t}
}

func (c *cgroupTestUtil) cleanup() {
	os.RemoveAll(c.tempDir)
}

// Write the specified contents on the mock of the specified cgroup files.
func (c *cgroupTestUtil) writeFileContents(fileContents map[string]string) {
	for file, contents := range fileContents {
		err := writeFile(c.CgroupPath, file, contents)
		if err != nil {
			c.t.Fatal(err)
		}
	}
}

// Expect the specified stats.
func expectStats(t *testing.T, expected, actual map[string]int64) {
	for stat, expectedValue := range expected {
		actualValue, ok := actual[stat]
		if !ok {
			log.Printf("Expected stat %s to exist: %s", stat, actual)
			t.Fail()
		} else if actualValue != expectedValue {
			log.Printf("Expected stats %s to have value %f but had %f instead", stat, expectedValue, actualValue)
			t.Fail()
		}
	}
}