Added a test acceptance for the new functionality.

GOOGLE_COMPUTE_DISK_SNAPSHOT_URI must be set to a valid snapshot's uri like one of the output of
gcloud compute snapshots list --uri

GOOGLE_COMPUTE_DISK_SNAPSHOT_URI should be replaced by a proper snapshot made by TF (#11690)

builtin/providers/google/provider_test.go

@@ -78,6 +78,10 @@ func testAccPreCheck(t *testing.T) {
 	if v := os.Getenv("GOOGLE_XPN_HOST_PROJECT"); v == "" {
 		t.Fatal("GOOGLE_XPN_HOST_PROJECT must be set for acceptance tests")
 	}
+
+	if v := os.Getenv("GOOGLE_COMPUTE_DISK_SNAPSHOT_URI"); v == "" {
+		t.Fatal("GOOGLE_COMPUTE_DISK_SNAPSHOT_URI must be set for acceptance tests")
+	}
 }
 
 func TestProvider_getRegionFromZone(t *testing.T) {

builtin/providers/google/resource_compute_disk_test.go

@@ -2,6 +2,7 @@ package google
 
 import (
 	"fmt"
+	"os"
 	"testing"
 
 	"github.com/hashicorp/terraform/helper/acctest"
@@ -30,6 +31,26 @@ func TestAccComputeDisk_basic(t *testing.T) {
 	})
 }
 
+func TestAccComputeDisk_from_snapshot_uri(t *testing.T) {
+	diskName := fmt.Sprintf("tf-test-%s", acctest.RandString(10))
+	var disk compute.Disk
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckComputeDiskDestroy,
+		Steps: []resource.TestStep{
+			resource.TestStep{
+				Config: testAccComputeDisk_from_snapshot_uri(diskName),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckComputeDiskExists(
+						"google_compute_disk.foobar", &disk),
+				),
+			},
+		},
+	})
+}
+
 func TestAccComputeDisk_encryption(t *testing.T) {
 	diskName := fmt.Sprintf("tf-test-%s", acctest.RandString(10))
 	var disk compute.Disk
@@ -130,6 +151,17 @@ resource "google_compute_disk" "foobar" {
 }`, diskName)
 }
 
+func testAccComputeDisk_from_snapshot_uri(diskName string) string {
+	uri := os.Getenv("GOOGLE_COMPUTE_DISK_SNAPSHOT_URI")
+	return fmt.Sprintf(`
+resource "google_compute_disk" "foobar" {
+	name = "%s"
+	snapshot = "%s"
+	type = "pd-ssd"
+	zone = "us-central1-a"
+}`, diskName, uri)
+}
+
 func testAccComputeDisk_encryption(diskName string) string {
 	return fmt.Sprintf(`
 resource "google_compute_disk" "foobar" {