erasureReadFile and erasureCreateFile testcases. (#2229)

* unit-tests: Unit tests for erasureCreateFile and erasureReadFile.

* appendFile() should return errXLWriteQuorum.

* TestErasureReadFileOffsetLength() tests erasureReadFile() for different offset and lengths.

* Fix for the failure seen in the erasure read unit test case. Issue #2227

* Move common erasure setup code to newErasureTestSetup()

* Review fixes. Add few more test cases for erasureReadFile.

erasure_test.go

@@ -18,7 +18,6 @@ package main
 
 import (
 	"bytes"
-	"crypto/rand"
 	"io/ioutil"
 	"os"
 	"testing"
@@ -187,24 +186,24 @@ func TestErasureDecode(t *testing.T) {
 	}
 }
 
-// Simulates a faulty disk for AppendFile()
-type AppendDiskDown struct {
-	*posix
+// Setup for erasureCreateFile and erasureReadFile tests.
+type erasureTestSetup struct {
+	dataBlocks   int
+	parityBlocks int
+	blockSize    int64
+	diskPaths    []string
+	disks        []StorageAPI
 }
 
-func (a AppendDiskDown) AppendFile(volume string, path string, buf []byte) error {
-	return errFaultyDisk
+// Removes the temporary disk directories.
+func (e erasureTestSetup) Remove() {
+	for _, path := range e.diskPaths {
+		removeAll(path)
+	}
 }
 
-// Test erasureCreateFile()
-// TODO:
-// * check when more disks are down.
-// * verify written content by using erasureReadFile.
-func TestErasureCreateFile(t *testing.T) {
-	// Initialize environment needed for the test.
-	dataBlocks := 7
-	parityBlocks := 7
-	blockSize := int64(blockSizeV1)
+// Returns an initialized setup for erasure tests.
+func newErasureTestSetup(dataBlocks int, parityBlocks int, blockSize int64) (*erasureTestSetup, error) {
 	diskPaths := make([]string, dataBlocks+parityBlocks)
 	disks := make([]StorageAPI, len(diskPaths))
 
@@ -212,44 +211,16 @@ func TestErasureCreateFile(t *testing.T) {
 		var err error
 		diskPaths[i], err = ioutil.TempDir(os.TempDir(), "minio-")
 		if err != nil {
-			t.Fatal("Unable to create tmp dir", err)
+			return nil, err
 		}
-		defer removeAll(diskPaths[i])
 		disks[i], err = newPosix(diskPaths[i])
 		if err != nil {
-			t.Fatal(err)
+			return nil, err
 		}
 		err = disks[i].MakeVol("testbucket")
 		if err != nil {
-			t.Fatal(err)
+			return nil, err
 		}
 	}
-
-	// Prepare a slice of 1MB with random data.
-	data := make([]byte, 1*1024*1024)
-	_, err := rand.Read(data)
-	if err != nil {
-		t.Fatal(err)
-	}
-	// Test when all disks are up.
-	size, _, err := erasureCreateFile(disks, "testbucket", "testobject1", bytes.NewReader(data), blockSize, dataBlocks, parityBlocks, dataBlocks+1)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if size != int64(len(data)) {
-		t.Errorf("erasureCreateFile returned %d, expected %d", size, len(data))
-	}
-
-	// Two disks down.
-	disks[4] = AppendDiskDown{disks[4].(*posix)}
-	disks[5] = AppendDiskDown{disks[5].(*posix)}
-
-	// Test when two disks are down.
-	size, _, err = erasureCreateFile(disks, "testbucket", "testobject2", bytes.NewReader(data), blockSize, dataBlocks, parityBlocks, dataBlocks+1)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if size != int64(len(data)) {
-		t.Errorf("erasureCreateFile returned %d, expected %d", size, len(data))
-	}
+	return &erasureTestSetup{dataBlocks, parityBlocks, blockSize, diskPaths, disks}, nil
 }