add wrapper around ioutil.ReadFile. (#226)

* add wrapper around ioutil.ReadFile.

* rename ReadFromFile to ReadFile

* refactor interna/ioutil_wrapper.go to util_test.go

metrics_proto_api_test.go

@@ -17,7 +17,6 @@ package stackdriver_test
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
 	"net"
 	"strings"
 	"sync"
@@ -427,7 +426,7 @@ func readTestCaseFromFiles(t *testing.T, filename string) *testCases {
 	}
 
 	// Read input Metrics proto.
-	f, err := ioutil.ReadFile("testdata/" + filename + "/inMetrics.txt")
+	f, err := readFile("testdata/" + filename + "/inMetrics.txt")
 	if err != nil {
 		t.Fatalf("error opening in file " + filename)
 	}
@@ -443,7 +442,7 @@ func readTestCaseFromFiles(t *testing.T, filename string) *testCases {
 	}
 
 	// Read expected output CreateMetricDescriptorRequest proto.
-	f, err = ioutil.ReadFile("testdata/" + filename + "/outMDR.txt")
+	f, err = readFile("testdata/" + filename + "/outMDR.txt")
 	if err != nil {
 		t.Fatalf("error opening in file " + filename)
 	}
@@ -461,7 +460,7 @@ func readTestCaseFromFiles(t *testing.T, filename string) *testCases {
 	}
 
 	// Read expected output CreateTimeSeriesRequest proto.
-	f, err = ioutil.ReadFile("testdata/" + filename + "/outTSR.txt")
+	f, err = readFile("testdata/" + filename + "/outTSR.txt")
 	if err != nil {
 		t.Fatalf("error opening in file " + filename)
 	}
@@ -480,7 +479,7 @@ func readTestCaseFromFiles(t *testing.T, filename string) *testCases {
 
 func readTestResourcesFiles(t *testing.T, filename string) ([]*resourcepb.Resource, []*monitoredrespb.MonitoredResource) {
 	// Read input Resource proto.
-	f, err := ioutil.ReadFile("testdata/" + filename + "/in.txt")
+	f, err := readFile("testdata/" + filename + "/in.txt")
 	if err != nil {
 		t.Fatalf("error opening in file " + filename)
 	}
@@ -497,7 +496,7 @@ func readTestResourcesFiles(t *testing.T, filename string) ([]*resourcepb.Resour
 	}
 
 	// Read output Resource proto.
-	f, err = ioutil.ReadFile("testdata/" + filename + "/out.txt")
+	f, err = readFile("testdata/" + filename + "/out.txt")
 	if err != nil {
 		t.Fatalf("error opening out file " + filename)
 	}

util_test.go

@@ -0,0 +1,24 @@
+// Copyright 2019, OpenCensus 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 stackdriver_test
+
+import (
+	"io/ioutil"
+)
+
+// readFile is a wrapper to read a file. It is meant for internal use for testing.
+func readFile(filename string) ([]byte, error) {
+	return ioutil.ReadFile(filename)
+}