add unit tests for caching

Author: nkubala

util/file_cache_test.go

@@ -0,0 +1,77 @@
+/*
+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 util
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/GoogleCloudPlatform/container-diff/pkg/cache"
+)
+
+var c *cache.FileCache
+
+func TestCacheData(t *testing.T) {
+	data := "this is a test of caching some bytes. this could be any data."
+	cacheAndTest(t, data, "sha256:realdata")
+}
+
+func TestCacheEmpty(t *testing.T) {
+	cacheAndTest(t, "", "sha256:emptydata")
+}
+
+func cacheAndTest(t *testing.T, testStr string, layerId string) {
+	byteArr := []byte(testStr)
+	r := bytes.NewReader(byteArr)
+
+	if c.HasLayer(layerId) {
+		t.Errorf("cache already has test layer %s", layerId)
+	}
+	c.SetLayer(layerId, r)
+
+	if !c.HasLayer(layerId) {
+		t.Errorf("layer %s not successfully cached", layerId)
+	}
+	cachedLayer, err := c.GetLayer(layerId)
+	if err != nil {
+		t.Errorf(err.Error())
+	}
+	cachedData, err := ioutil.ReadAll(cachedLayer)
+	cachedStr := string(cachedData)
+	if cachedStr != testStr {
+		t.Errorf("cached data %s does not match original: %s", cachedStr, testStr)
+	}
+}
+
+func TestMain(m *testing.M) {
+	var err error
+	cacheDir, err := ioutil.TempDir("", ".cache")
+	if err != nil {
+		fmt.Printf(err.Error())
+		os.Exit(1)
+	}
+	defer os.RemoveAll(cacheDir)
+	c, err = cache.NewFileCache(cacheDir)
+	if err != nil {
+		fmt.Printf(err.Error())
+		os.Exit(1)
+	}
+	os.Exit(m.Run())
+}