add network integration test

pkg/cluster/internal/providers/docker/network_test.go

@@ -18,9 +18,65 @@ package docker
 
 import (
 	"fmt"
+	"regexp"
+	"strings"
 	"testing"
+
+	"sigs.k8s.io/kind/pkg/errors"
+	"sigs.k8s.io/kind/pkg/exec"
+
+	"sigs.k8s.io/kind/pkg/internal/integration"
 )
 
+func TestIntegrationEnsureNetworkConcurrent(t *testing.T) {
+	integration.MaybeSkip(t)
+
+	testNetworkName := "integration-test-ensure-kind-network"
+
+	// cleanup
+	cleanup := func() {
+		exec.Command("docker", "network", "rm", testNetworkName).Run()
+	}
+	cleanup()
+	defer cleanup()
+
+	// this is more than enough to trigger race conditions
+	networkConcurrency := 10
+
+	// Create multiple networks concurrently
+	errCh := make(chan error, networkConcurrency)
+	for i := 0; i < networkConcurrency; i++ {
+		go func() {
+			errCh <- ensureNetwork(testNetworkName)
+		}()
+	}
+	for i := 0; i < networkConcurrency; i++ {
+		if err := <-errCh; err != nil {
+			t.Errorf("error creating network: %v", err)
+			rerr := exec.RunErrorForError(err)
+			if rerr != nil {
+				t.Errorf("%q", rerr.Output)
+				t.Errorf("%v", strings.HasPrefix(string(rerr.Output), "Error response from daemon: network with name") && strings.HasSuffix(string(rerr.Output), "already exists\n"))
+			}
+			t.Errorf("%+v", errors.StackTrace(err))
+		}
+	}
+
+	cmd := exec.Command(
+		"docker", "network", "ls",
+		fmt.Sprintf("--filter=name=^%s$", regexp.QuoteMeta(testNetworkName)),
+		"--format={{.Name}}",
+	)
+
+	lines, err := exec.OutputLines(cmd)
+	if err != nil {
+		t.Errorf("obtaining the docker networks")
+	}
+	if len(lines) != 1 {
+		t.Errorf("wrong number of networks created: %d", len(lines))
+	}
+}
+
 func Test_generateULASubnetFromName(t *testing.T) {
 	t.Parallel()
 	cases := []struct {

pkg/internal/integration/integration.go

@@ -0,0 +1,33 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package integration
+
+import "testing"
+
+// *testing.T methods used by assert
+type testingDotT interface {
+	Skip(args ...interface{})
+}
+
+// MaybeSkip skips if integration tests should be skipped
+// currently this is when testing.Short() is true
+// This should be called at the beginning of an integration test
+func MaybeSkip(t testingDotT) {
+	if testing.Short() {
+		t.Skip("Skipping integration test due to -short")
+	}
+}