Vendor dependencies for GCS

vendor/cloud.google.com/go/spanner/backoff_test.go

@@ -0,0 +1,62 @@
+/*
+Copyright 2017 Google Inc. All Rights Reserved.
+
+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 spanner
+
+import (
+	"math"
+	"time"
+
+	"testing"
+)
+
+// Test if exponential backoff helper can produce correct series of
+// retry delays.
+func TestBackoff(t *testing.T) {
+	b := exponentialBackoff{minBackoff, maxBackoff}
+	tests := []struct {
+		retries int
+		min     time.Duration
+		max     time.Duration
+	}{
+		{
+			retries: 0,
+			min:     minBackoff,
+			max:     minBackoff,
+		},
+		{
+			retries: 1,
+			min:     minBackoff,
+			max:     time.Duration(rate * float64(minBackoff)),
+		},
+		{
+			retries: 3,
+			min:     time.Duration(math.Pow(rate, 3) * (1 - jitter) * float64(minBackoff)),
+			max:     time.Duration(math.Pow(rate, 3) * float64(minBackoff)),
+		},
+		{
+			retries: 1000,
+			min:     time.Duration((1 - jitter) * float64(maxBackoff)),
+			max:     maxBackoff,
+		},
+	}
+	for _, test := range tests {
+		got := b.delay(test.retries)
+		if float64(got) < float64(test.min) || float64(got) > float64(test.max) {
+			t.Errorf("delay(%v) = %v, want in range [%v, %v]", test.retries, got, test.min, test.max)
+		}
+	}
+}