Started working on unit tests

Fixed some bugs in the CSVColumn processor

fmt_test.go

@@ -1,7 +1,40 @@
 package scriptx_test
 
-import "testing"
+import (
+	"testing"
+
+	"github.com/bitfield/script"
+	"github.com/lmika/scriptx"
+	"github.com/stretchr/testify/assert"
+)
 
 func TestPrintf(t *testing.T) {
-	t.Log("Hello")
-}
+	t.Run("should format each line according to the pattern", func(t *testing.T) {
+		verifyPipeLines(t, func(p *script.Pipe) *script.Pipe {
+			return p.Filter(scriptx.Printf("Line: [%v]"))
+		}, []string{
+			"Line 1",
+			"Line 2",
+			"Line 3",
+		}, []string{
+			"Line: [Line 1]",
+			"Line: [Line 2]",
+			"Line: [Line 3]",
+		})
+	})
+}
+
+func verifyPipeLines(t *testing.T, fn func(p *script.Pipe) *script.Pipe, inLines []string, expOut []string) {
+	pipe := script.Slice(inLines)
+	outLines, err := fn(pipe).Slice()
+
+	assert.NoError(t, err)
+	assert.Equal(t, expOut, outLines)
+}
+
+func verifyPipeErr(t *testing.T, fn func(p *script.Pipe) *script.Pipe, inLines []string) {
+	pipe := script.Slice(inLines)
+	_, err := fn(pipe).Slice()
+
+	assert.Error(t, err)
+}