Add one level of outer most test

cmd/root.go

@@ -78,28 +78,36 @@ Most suitable for csv files created from database tables`,
 			DeltaFilename:          deltaFilename,
 		}
 
-		if err := ctx.Validate(fs); err != nil {
-			return err
-		}
+		return runContext(ctx, fs, os.Stdout, os.Stderr)
+	},
+}
 
-		baseConfig, err := ctx.BaseDigestConfig(fs)
-		if err != nil {
-			return fmt.Errorf("error opening base-file %s: %v", baseFilename, err)
-		}
-		deltaConfig, err := ctx.DeltaDigestConfig(fs)
-		if err != nil {
-			return fmt.Errorf("error opening delta-file %s: %v", deltaFilename, err)
-		}
-		defer ctx.Close()
+func runContext(
+	ctx Context,
+	fs afero.Fs,
+	outputStream,
+	errorStream io.Writer) error {
+	if err := ctx.Validate(fs); err != nil {
+		return err
+	}
 
-		diff, err := digest.Diff(baseConfig, deltaConfig)
+	baseConfig, err := ctx.BaseDigestConfig(fs)
+	if err != nil {
+		return fmt.Errorf("error opening base-file %s: %v", ctx.BaseFilename, err)
+	}
+	deltaConfig, err := ctx.DeltaDigestConfig(fs)
+	if err != nil {
+		return fmt.Errorf("error opening delta-file %s: %v", ctx.DeltaFilename, err)
+	}
+	defer ctx.Close()
 
-		if err != nil {
-			return err
-		}
+	diff, err := digest.Diff(baseConfig, deltaConfig)
 
-		return NewFormatter(os.Stdout, os.Stderr, ctx).Format(diff)
-	},
+	if err != nil {
+		return err
+	}
+
+	return NewFormatter(outputStream, errorStream, ctx).Format(diff)
 }
 
 func isValidFile(path string) error {

cmd/root_test.go

@@ -0,0 +1,66 @@
+package cmd
+
+import (
+	"bytes"
+	"github.com/aswinkarthik/csvdiff/pkg/digest"
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/assert"
+	"os"
+	"testing"
+)
+
+func TestRunContext(t *testing.T) {
+	t.Run("should find diff in happy path", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
+		{
+			baseContent := []byte(`id,name,age,desc
+0,tom,2,developer
+2,ryan,20,qa
+4,emin,40,pm
+
+`)
+			err := afero.WriteFile(fs, "/base.csv", baseContent, os.ModePerm)
+			assert.NoError(t, err)
+		}
+		{
+			deltaContent := []byte(`id,name,age,desc
+0,tom,2,developer
+1,caprio,3,developer
+2,ryan,23,qa
+`)
+			err := afero.WriteFile(fs, "/delta.csv", deltaContent, os.ModePerm)
+			assert.NoError(t, err)
+		}
+
+		ctx := Context{
+			Format:                 "json",
+			BaseFilename:           "/base.csv",
+			DeltaFilename:          "/delta.csv",
+			PrimaryKeyPositions:    digest.Positions{0},
+			ValueColumnPositions:   digest.Positions{1, 2},
+			IncludeColumnPositions: digest.Positions{0, 1, 2},
+		}
+		outStream := &bytes.Buffer{}
+		errStream := &bytes.Buffer{}
+
+		err := runContext(ctx, fs, outStream, errStream)
+		expected := `{
+  "Additions": [
+    "1,caprio,3"
+  ],
+  "Modifications": [
+    {
+      "Original": "2,ryan,20",
+      "Current": "2,ryan,23"
+    }
+  ],
+  "Deletions": [
+    "4,emin,40"
+  ]
+}`
+
+		assert.NoError(t, err)
+		assert.Equal(t, expected, outStream.String())
+
+	})
+}