diff --git a/cmd/config.go b/cmd/config.go
index 7ee8019..416ef4b 100644
--- a/cmd/config.go
+++ b/cmd/config.go
@@ -1,7 +1,8 @@
 package cmd
 
 import (
-	"errors"
+	"fmt"
+	"github.com/spf13/afero"
 	"strings"
 
 	"github.com/aswinkarthik/csvdiff/pkg/digest"
@@ -13,6 +14,8 @@ type Config struct {
 	ValueColumnPositions   []int
 	IncludeColumnPositions []int
 	Format                 string
+	BaseFilename           string
+	DeltaFilename          string
 }
 
 // GetPrimaryKeys is to return the --primary-key flags as digest.Positions array.
@@ -42,13 +45,52 @@ func (c Config) GetIncludeColumnPositions() digest.Positions {
 
 // Validate validates the config object
 // and returns error if not valid.
-func (c *Config) Validate() error {
+func (c *Config) Validate(fs afero.Fs) error {
+	{
+		// format validation
 
-	for _, format := range allFormats {
-		if strings.ToLower(c.Format) == format {
-			return nil
+		formatFound := false
+		for _, format := range allFormats {
+			if strings.ToLower(c.Format) == format {
+				formatFound = true
+			}
+		}
+		if !formatFound {
+			return fmt.Errorf("specified format is not valid")
+		}
+	}
+
+	{
+		// base-file validation
+
+		if exists, err := afero.Exists(fs, c.BaseFilename); err != nil {
+			return fmt.Errorf("error reading base-file %s: %v", c.BaseFilename, err)
+		} else if !exists {
+			return fmt.Errorf("base-file %s does not exits", c.BaseFilename)
+		}
+
+		if isDir, err := afero.IsDir(fs, c.BaseFilename); err != nil {
+			return fmt.Errorf("error reading base-file %s: %v", c.BaseFilename, err)
+		} else if isDir {
+			return fmt.Errorf("base-file %s should be a file", c.BaseFilename)
+		}
+	}
+
+	{
+		// delta file validation
+
+		if exists, err := afero.Exists(fs, c.DeltaFilename); err != nil {
+			return fmt.Errorf("error reading delta-file %s: %v", c.DeltaFilename, err)
+		} else if !exists {
+			return fmt.Errorf("delta-file %s does not exits", c.DeltaFilename)
+		}
+
+		if isDir, err := afero.IsDir(fs, c.DeltaFilename); err != nil {
+			return fmt.Errorf("error reading delta-file %s: %v", c.DeltaFilename, err)
+		} else if isDir {
+			return fmt.Errorf("delta-file %s should be a file", c.DeltaFilename)
 		}
 	}
 
-	return errors.New("Specified format is not valid")
+	return nil
 }
diff --git a/cmd/config_test.go b/cmd/config_test.go
index 46d7102..a7b8fba 100644
--- a/cmd/config_test.go
+++ b/cmd/config_test.go
@@ -1,6 +1,8 @@
 package cmd_test
 
 import (
+	"github.com/spf13/afero"
+	"os"
 	"testing"
 
 	"github.com/aswinkarthik/csvdiff/cmd"
@@ -31,15 +33,67 @@ func TestValueColumnPositions(t *testing.T) {
 }
 
 func TestConfigValidate(t *testing.T) {
-	config := &cmd.Config{}
-	assert.Error(t, config.Validate())
+	t.Run("should validate format", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
 
-	config = &cmd.Config{Format: "rowmark"}
-	assert.NoError(t, config.Validate())
+		config := validConfig(t, fs)
 
-	config = &cmd.Config{Format: "rowMARK"}
-	assert.NoError(t, config.Validate())
+		config.Format = ""
+		assert.Error(t, config.Validate(fs))
 
-	config = &cmd.Config{Format: "json"}
-	assert.NoError(t, config.Validate())
+		config.Format = "rowmark"
+		assert.NoError(t, config.Validate(fs))
+
+		config.Format = "rowMARK"
+		assert.NoError(t, config.Validate(fs))
+
+		config.Format = "json"
+		assert.NoError(t, config.Validate(fs))
+	})
+
+	t.Run("should validate base file existence", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
+
+		config := &cmd.Config{Format: "json", BaseFilename: "/base.csv", DeltaFilename: "/delta.csv"}
+		err := config.Validate(fs)
+		assert.EqualError(t, err, "base-file /base.csv does not exits")
+	})
+
+	t.Run("should validate if base file or delta file is a file", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
+		err := fs.Mkdir("/base.csv", os.ModePerm)
+		assert.NoError(t, err)
+
+		config := &cmd.Config{Format: "json", BaseFilename: "/base.csv", DeltaFilename: "/delta.csv"}
+		err = config.Validate(fs)
+		assert.EqualError(t, err, "base-file /base.csv should be a file")
+
+		_, err = fs.Create("/valid-base.csv")
+		err = fs.Mkdir("/delta.csv", os.ModePerm)
+		assert.NoError(t, err)
+
+		config = &cmd.Config{Format: "json", BaseFilename: "/valid-base.csv", DeltaFilename: "/delta.csv"}
+		err = config.Validate(fs)
+		assert.EqualError(t, err, "delta-file /delta.csv should be a file")
+	})
+
+	t.Run("should validate if both base and delta file exist", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
+		_, err := fs.Create("/base.csv")
+		assert.NoError(t, err)
+		_, err = fs.Create("/delta.csv")
+		assert.NoError(t, err)
+
+		config := &cmd.Config{Format: "json", BaseFilename: "/base.csv", DeltaFilename: "/delta.csv"}
+		err = config.Validate(fs)
+		assert.NoError(t, err)
+	})
+}
+
+func validConfig(t *testing.T, fs afero.Fs) *cmd.Config {
+	_, err := fs.Create("/base.csv")
+	assert.NoError(t, err)
+	_, err = fs.Create("/delta.csv")
+	assert.NoError(t, err)
+	return &cmd.Config{Format: "json", BaseFilename: "/base.csv", DeltaFilename: "/delta.csv"}
 }
diff --git a/cmd/root.go b/cmd/root.go
index 770241d..105c494 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -23,6 +23,7 @@ package cmd
 import (
 	"fmt"
 	"github.com/fatih/color"
+	"github.com/spf13/afero"
 	"io"
 	"os"
 	"strings"
@@ -64,20 +65,36 @@ Most suitable for csv files created from database tables`,
 		if timed {
 			defer timeTrack(time.Now(), "csvdiff")
 		}
+		fs := afero.NewOsFs()
 
-		baseFile := newReadCloser(args[0])
-		defer baseFile.Close()
-		deltaFile := newReadCloser(args[1])
-		defer deltaFile.Close()
+		baseFilename := args[0]
+		deltaFilename := args[1]
+
+		baseFile, err := newReadCloser(baseFilename)
+		if err != nil {
+			return fmt.Errorf("error opening base-file %s: %v", baseFilename, err)
+		}
+
+		deltaFile, err := newReadCloser(deltaFilename)
+		if err != nil {
+			return fmt.Errorf("error opening delta-file %s: %v", deltaFilename, err)
+		}
+
+		defer func() {
+			_ = baseFile.Close()
+			_ = deltaFile.Close()
+		}()
 
 		config := Config{
 			IncludeColumnPositions: includeColumnPositions,
 			Format:                 format,
 			PrimaryKeyPositions:    primaryKeyPositions,
 			ValueColumnPositions:   valueColumnPositions,
+			BaseFilename:           baseFilename,
+			DeltaFilename:          deltaFilename,
 		}
 
-		if err := config.Validate(); err != nil {
+		if err := config.Validate(fs); err != nil {
 			return err
 		}
 
@@ -151,16 +168,16 @@ func init() {
 	rootCmd.Flags().BoolVarP(&timed, "time", "", false, "Measure time")
 }
 
-func newReadCloser(filename string) io.ReadCloser {
+func newReadCloser(filename string) (io.ReadCloser, error) {
 	file, err := os.Open(filename)
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 
-	return file
+	return file, nil
 }
 
 func timeTrack(start time.Time, name string) {
 	elapsed := time.Since(start)
-	fmt.Fprintln(os.Stderr, fmt.Sprintf("%s took %s", name, elapsed))
+	_, _ = fmt.Fprintln(os.Stderr, fmt.Sprintf("%s took %s", name, elapsed))
 }
diff --git a/go.mod b/go.mod
index fd1a46c..a74f26a 100644
--- a/go.mod
+++ b/go.mod
@@ -6,6 +6,7 @@ require (
 	github.com/fatih/color v1.7.0
 	github.com/mattn/go-colorable v0.1.2 // indirect
 	github.com/spaolacci/murmur3 v1.1.0 // indirect
+	github.com/spf13/afero v1.1.2
 	github.com/spf13/cobra v0.0.5
 	github.com/stretchr/testify v1.3.0
 	golang.org/x/sys v0.0.0-20190804053845-51ab0e2deafa // indirect
diff --git a/go.sum b/go.sum
index e412cc7..0b0dbf7 100644
--- a/go.sum
+++ b/go.sum
@@ -35,6 +35,7 @@ github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72 h1:qLC7fQah7D6K1
 github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
 github.com/spaolacci/murmur3 v1.1.0 h1:7c1g84S4BPRrfL5Xrdp6fOJ206sU9y293DDHaoy0bLI=
 github.com/spaolacci/murmur3 v1.1.0/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
+github.com/spf13/afero v1.1.2 h1:m8/z1t7/fwjysjQRYbP0RD+bUIF/8tJwPdEZsI83ACI=
 github.com/spf13/afero v1.1.2/go.mod h1:j4pytiNVoe2o6bmDsKpLACNPDBIoEAkihy7loJ1B0CQ=
 github.com/spf13/cast v1.3.0/go.mod h1:Qx5cxh0v+4UWYiBimWS+eyWzqEqokIECu5etghLkUJE=
 github.com/spf13/cobra v0.0.5 h1:f0B+LkLX6DtmRH1isoNA9VTtNUK9K8xYd28JNNfOv/s=
@@ -55,6 +56,7 @@ golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223 h1:DH4skfRX4EBpamg7iV4ZlCpbl
 golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190804053845-51ab0e2deafa h1:KIDDMLT1O0Nr7TSxp8xM5tJcdn8tgyAONntO829og1M=
 golang.org/x/sys v0.0.0-20190804053845-51ab0e2deafa/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
diff --git a/pkg/digest/config.go b/pkg/digest/config.go
index 8ad6b16..c2c0428 100644
--- a/pkg/digest/config.go
+++ b/pkg/digest/config.go
@@ -8,7 +8,6 @@ import "io"
 // Key: The primary key positions
 // Value: The Value positions that needs to be compared for diff
 // Include: Include these positions in output. It is Value positions by default.
-// KeepSource: return the source and target string if diff is computed
 type Config struct {
 	Key     Positions
 	Value   Positions