storage: readObject method for tests

Add a method to simplify some tests.

Change-Id: I6e38ec01d9cfd8af72a45731ad9e1d9aa30ce39c
Reviewed-on: https://code-review.googlesource.com/8991
Reviewed-by: Jonathan Amsterdam <jba@google.com>

storage/integration_test.go

@@ -519,18 +519,13 @@ func TestObjects(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	rc, err := publicClient.Bucket(bucket).Object(publicObj).NewReader(ctx)
-	if err != nil {
-		t.Error(err)
-	}
-	slurp, err := ioutil.ReadAll(rc)
+
+	slurp, err := readObject(ctx, publicClient.Bucket(bucket).Object(publicObj))
 	if err != nil {
-		t.Errorf("ReadAll failed with %v", err)
-	}
-	if !bytes.Equal(slurp, contents[publicObj]) {
+		t.Errorf("readObject failed with %v", err)
+	} else if !bytes.Equal(slurp, contents[publicObj]) {
 		t.Errorf("Public object's content: got %q, want %q", slurp, contents[publicObj])
 	}
-	rc.Close()
 
 	// Test writer error handling.
 	wc := publicClient.Bucket(bucket).Object(publicObj).NewWriter(ctx)
@@ -567,7 +562,7 @@ func TestObjects(t *testing.T) {
 	if _, err := c.Run(ctx); err != nil {
 		t.Fatalf("ComposeFrom error: %v", err)
 	}
-	rc, err = compDst.NewReader(ctx)
+	rc, err := compDst.NewReader(ctx)
 	if err != nil {
 		t.Fatalf("compDst.NewReader: %v", err)
 	}
@@ -797,20 +792,24 @@ func TestZeroSizedObject(t *testing.T) {
 	defer obj.Delete(ctx)
 
 	// Check we can read it too.
-	r, err := obj.NewReader(ctx)
+	body, err := readObject(ctx, obj)
 	if err != nil {
-		t.Fatalf("NewReader: %v", err)
-	}
-	defer r.Close()
-	body, err := ioutil.ReadAll(r)
-	if err != nil {
-		t.Fatalf("ioutil.ReadAll: %v", err)
+		t.Fatalf("readObject: %v", err)
 	}
 	if len(body) != 0 {
 		t.Errorf("Body is %v, want empty []byte{}", body)
 	}
 }
 
+func readObject(ctx context.Context, obj *ObjectHandle) ([]byte, error) {
+	r, err := obj.NewReader(ctx)
+	if err != nil {
+		return nil, err
+	}
+	defer r.Close()
+	return ioutil.ReadAll(r)
+}
+
 // cleanup deletes the bucket used for testing, as well as old
 // testing buckets that weren't cleaned previously.
 func cleanup() error {