Separate go module for client tests

Will help us drop dependency to github.com/Microsoft/hcsshim/test in the
main go.mod

Signed-off-by: Davanum Srinivas <davanum@gmail.com>

integration/client/export_test.go

@@ -0,0 +1,85 @@
+/*
+   Copyright The containerd 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 containerd
+
+import (
+	"archive/tar"
+	"bytes"
+	"io"
+	"runtime"
+	"testing"
+
+	. "github.com/containerd/containerd"
+	"github.com/containerd/containerd/images/archive"
+	"github.com/containerd/containerd/platforms"
+)
+
+// TestExport exports testImage as a tar stream
+func TestExport(t *testing.T) {
+	// TODO: support windows
+	if testing.Short() || runtime.GOOS == "windows" {
+		t.Skip()
+	}
+	ctx, cancel := testContext(t)
+	defer cancel()
+
+	client, err := New(address)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer client.Close()
+
+	_, err = client.Fetch(ctx, testImage)
+	if err != nil {
+		t.Fatal(err)
+	}
+	wb := bytes.NewBuffer(nil)
+	err = client.Export(ctx, wb, archive.WithPlatform(platforms.Default()), archive.WithImage(client.ImageService(), testImage))
+	if err != nil {
+		t.Fatal(err)
+	}
+	assertOCITar(t, bytes.NewReader(wb.Bytes()))
+}
+
+func assertOCITar(t *testing.T, r io.Reader) {
+	// TODO: add more assertion
+	tr := tar.NewReader(r)
+	foundOCILayout := false
+	foundIndexJSON := false
+	for {
+		h, err := tr.Next()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		if h.Name == "oci-layout" {
+			foundOCILayout = true
+		}
+		if h.Name == "index.json" {
+			foundIndexJSON = true
+		}
+	}
+	if !foundOCILayout {
+		t.Error("oci-layout not found")
+	}
+	if !foundIndexJSON {
+		t.Error("index.json not found")
+	}
+}