diff --git a/pkg/yqlib/json_converter.go b/pkg/marshal/json_converter.go
similarity index 54%
rename from pkg/yqlib/json_converter.go
rename to pkg/marshal/json_converter.go
index e837188..d42a001 100644
--- a/pkg/yqlib/json_converter.go
+++ b/pkg/marshal/json_converter.go
@@ -1,4 +1,4 @@
-package yqlib
+package marshal
 
 import (
 	"encoding/json"
@@ -8,21 +8,31 @@ import (
 	yaml "github.com/mikefarah/yaml/v2"
 )
 
-func JsonToString(context interface{}) (string, error) {
-	out, err := json.Marshal(toJSON(context))
+type JsonConverter interface {
+	JsonToString(context interface{}) (string, error)
+}
+
+type jsonConverter struct {}
+
+func NewJsonConverter() JsonConverter {
+	return &jsonConverter{}
+}
+
+func (j *jsonConverter) JsonToString(context interface{}) (string, error) {
+	out, err := json.Marshal(j.toJSON(context))
 	if err != nil {
 		return "", fmt.Errorf("error printing yaml as json: %v", err)
 	}
 	return string(out), nil
 }
 
-func toJSON(context interface{}) interface{} {
+func (j *jsonConverter) toJSON(context interface{}) interface{} {
 	switch context := context.(type) {
 	case []interface{}:
 		oldArray := context
 		newArray := make([]interface{}, len(oldArray))
 		for index, value := range oldArray {
-			newArray[index] = toJSON(value)
+			newArray[index] = j.toJSON(value)
 		}
 		return newArray
 	case yaml.MapSlice:
@@ -30,11 +40,11 @@ func toJSON(context interface{}) interface{} {
 		newMap := make(map[string]interface{})
 		for _, entry := range oldMap {
 			if str, ok := entry.Key.(string); ok {
-				newMap[str] = toJSON(entry.Value)
+				newMap[str] = j.toJSON(entry.Value)
 			} else if i, ok := entry.Key.(int); ok {
-				newMap[strconv.Itoa(i)] = toJSON(entry.Value)
+				newMap[strconv.Itoa(i)] = j.toJSON(entry.Value)
 			} else if b, ok := entry.Key.(bool); ok {
-				newMap[strconv.FormatBool(b)] = toJSON(entry.Value)
+				newMap[strconv.FormatBool(b)] = j.toJSON(entry.Value)
 			}
 		}
 		return newMap
diff --git a/pkg/yqlib/json_converter_test.go b/pkg/marshal/json_converter_test.go
similarity index 76%
rename from pkg/yqlib/json_converter_test.go
rename to pkg/marshal/json_converter_test.go
index ae1c08d..e568902 100644
--- a/pkg/yqlib/json_converter_test.go
+++ b/pkg/marshal/json_converter_test.go
@@ -1,4 +1,4 @@
-package yqlib
+package marshal
 
 import (
 	"testing"
@@ -11,7 +11,7 @@ func TestJsonToString(t *testing.T) {
 b:
   c: 2
 `)
-	got, _ := JsonToString(data)
+	got, _ := NewJsonConverter().JsonToString(data)
 	test.AssertResult(t, "{\"b\":{\"c\":2}}", got)
 }
 
@@ -21,7 +21,7 @@ func TestJsonToString_withIntKey(t *testing.T) {
 b:
   2: c
 `)
-	got, _ := JsonToString(data)
+	got, _ := NewJsonConverter().JsonToString(data)
 	test.AssertResult(t, `{"b":{"2":"c"}}`, got)
 }
 
@@ -31,7 +31,7 @@ func TestJsonToString_withBoolKey(t *testing.T) {
 b:
   false: c
 `)
-	got, _ := JsonToString(data)
+	got, _ := NewJsonConverter().JsonToString(data)
 	test.AssertResult(t, `{"b":{"false":"c"}}`, got)
 }
 
@@ -42,6 +42,6 @@ b:
   - item: one
   - item: two
 `)
-	got, _ := JsonToString(data)
+	got, _ := NewJsonConverter().JsonToString(data)
 	test.AssertResult(t, "{\"b\":[{\"item\":\"one\"},{\"item\":\"two\"}]}", got)
 }
diff --git a/pkg/yqlib/yaml_converter.go b/pkg/marshal/yaml_converter.go
similarity index 52%
rename from pkg/yqlib/yaml_converter.go
rename to pkg/marshal/yaml_converter.go
index 08eec17..a632ae9 100644
--- a/pkg/yqlib/yaml_converter.go
+++ b/pkg/marshal/yaml_converter.go
@@ -1,4 +1,4 @@
-package yqlib
+package marshal
 
 import (
 	yaml "github.com/mikefarah/yaml/v2"
@@ -6,16 +6,26 @@ import (
 	"strings"
 )
 
-func YamlToString(context interface{}, trimOutput bool) (string, error) {
+type YamlConverter interface {
+	YamlToString(context interface{}, trimOutput bool) (string, error)
+}
+
+type yamlConverter struct {}
+
+func NewYamlConverter() YamlConverter {
+	return &yamlConverter{}
+}
+
+func (y *yamlConverter) YamlToString(context interface{}, trimOutput bool) (string, error) {
 	switch context := context.(type) {
 	case string:
 		return context, nil
 	default:
-		return marshalContext(context, trimOutput)
+		return y.marshalContext(context, trimOutput)
 	}
 }
 
-func marshalContext(context interface{}, trimOutput bool) (string, error) {
+func (y *yamlConverter) marshalContext(context interface{}, trimOutput bool) (string, error) {
 	out, err := yaml.Marshal(context)
 
 	if err != nil {
diff --git a/pkg/yqlib/data_navigator.go b/pkg/yqlib/data_navigator.go
index 2b66dee..c0e4c58 100644
--- a/pkg/yqlib/data_navigator.go
+++ b/pkg/yqlib/data_navigator.go
@@ -7,9 +7,96 @@ import (
 	"strings"
 
 	yaml "github.com/mikefarah/yaml/v2"
+	logging "gopkg.in/op/go-logging.v1"
 )
 
-func matchesKey(key string, actual interface{}) bool {
+type DataNavigator interface {
+	ReadChildValue(child interface{}, remainingPaths []string) (interface{}, error)
+	UpdatedChildValue(child interface{}, remainingPaths []string, value interface{}) interface{}
+	DeleteChildValue(child interface{}, remainingPaths []string) (interface{}, error)
+}
+
+type navigator struct {
+	log *logging.Logger
+}
+
+func NewDataNavigator(l *logging.Logger) DataNavigator {
+	return &navigator {
+		log: l,
+	}
+}
+
+func (n *navigator) ReadChildValue(child interface{}, remainingPaths []string) (interface{}, error) {
+	if len(remainingPaths) == 0 {
+		return child, nil
+	}
+	return n.recurse(child, remainingPaths[0], remainingPaths[1:])
+}
+
+func (n *navigator) UpdatedChildValue(child interface{}, remainingPaths []string, value interface{}) interface{} {
+	if len(remainingPaths) == 0 {
+		return value
+	}
+	n.log.Debugf("UpdatedChildValue for child %v with path %v to set value %v", child, remainingPaths, value)
+	n.log.Debugf("type of child is %v", reflect.TypeOf(child))
+
+	switch child := child.(type) {
+	case nil:
+		if remainingPaths[0] == "+" || remainingPaths[0] == "*" {
+			return n.writeArray(child, remainingPaths, value)
+		}
+	case []interface{}:
+		_, nextIndexErr := strconv.ParseInt(remainingPaths[0], 10, 64)
+		arrayCommand := nextIndexErr == nil || remainingPaths[0] == "+" || remainingPaths[0] == "*"
+		if arrayCommand {
+			return n.writeArray(child, remainingPaths, value)
+		}
+	}
+	return n.writeMap(child, remainingPaths, value)
+}
+
+func (n *navigator) DeleteChildValue(child interface{}, remainingPaths []string) (interface{}, error) {
+	n.log.Debugf("DeleteChildValue for %v for %v\n", remainingPaths, child)
+	if len(remainingPaths) == 0 {
+		return child, nil
+	}
+	var head = remainingPaths[0]
+	var tail = remainingPaths[1:]
+	switch child := child.(type) {
+	case yaml.MapSlice:
+		return n.deleteMap(child, remainingPaths)
+	case []interface{}:
+		if head == "*" {
+			return n.deleteArraySplat(child, tail)
+		}
+		index, err := strconv.ParseInt(head, 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("error accessing array: %v", err)
+		}
+		return n.deleteArray(child, remainingPaths, index)
+	}
+	return child, nil
+}
+
+func (n *navigator) recurse(value interface{}, head string, tail []string) (interface{}, error) {
+	switch value := value.(type) {
+	case []interface{}:
+		if head == "*" {
+			return n.readArraySplat(value, tail)
+		}
+		index, err := strconv.ParseInt(head, 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("error accessing array: %v", err)
+		}
+		return n.readArray(value, index, tail)
+	case yaml.MapSlice:
+		return n.readMap(value, head, tail)
+	default:
+		return nil, nil
+	}
+}
+
+func (n *navigator) matchesKey(key string, actual interface{}) bool {
 	var actualString = fmt.Sprintf("%v", actual)
 	var prefixMatch = strings.TrimSuffix(key, "*")
 	if prefixMatch != key {
@@ -18,18 +105,18 @@ func matchesKey(key string, actual interface{}) bool {
 	return actualString == key
 }
 
-func entriesInSlice(context yaml.MapSlice, key string) []*yaml.MapItem {
+func (n *navigator) entriesInSlice(context yaml.MapSlice, key string) []*yaml.MapItem {
 	var matches = make([]*yaml.MapItem, 0)
 	for idx := range context {
 		var entry = &context[idx]
-		if matchesKey(key, entry.Key) {
+		if n.matchesKey(key, entry.Key) {
 			matches = append(matches, entry)
 		}
 	}
 	return matches
 }
 
-func getMapSlice(context interface{}) yaml.MapSlice {
+func (n *navigator) getMapSlice(context interface{}) yaml.MapSlice {
 	var mapSlice yaml.MapSlice
 	switch context := context.(type) {
 	case yaml.MapSlice:
@@ -40,7 +127,7 @@ func getMapSlice(context interface{}) yaml.MapSlice {
 	return mapSlice
 }
 
-func getArray(context interface{}) (array []interface{}, ok bool) {
+func (n *navigator) getArray(context interface{}) (array []interface{}, ok bool) {
 	switch context := context.(type) {
 	case []interface{}:
 		array = context
@@ -52,68 +139,46 @@ func getArray(context interface{}) (array []interface{}, ok bool) {
 	return
 }
 
-func writeMap(context interface{}, paths []string, value interface{}) interface{} {
-	log.Debugf("writeMap with path %v for %v to set value %v\n", paths, context, value)
+func (n *navigator) writeMap(context interface{}, paths []string, value interface{}) interface{} {
+	n.log.Debugf("writeMap with path %v for %v to set value %v\n", paths, context, value)
 
-	mapSlice := getMapSlice(context)
+	mapSlice := n.getMapSlice(context)
 
 	if len(paths) == 0 {
 		return context
 	}
 
-	children := entriesInSlice(mapSlice, paths[0])
+	children := n.entriesInSlice(mapSlice, paths[0])
 
 	if len(children) == 0 && paths[0] == "*" {
-		log.Debugf("\tNo matches, return map as is")
+		n.log.Debugf("\tNo matches, return map as is")
 		return context
 	}
 
 	if len(children) == 0 {
 		newChild := yaml.MapItem{Key: paths[0]}
 		mapSlice = append(mapSlice, newChild)
-		children = entriesInSlice(mapSlice, paths[0])
-		log.Debugf("\tAppended child at %v for mapSlice %v\n", paths[0], mapSlice)
+		children = n.entriesInSlice(mapSlice, paths[0])
+		n.log.Debugf("\tAppended child at %v for mapSlice %v\n", paths[0], mapSlice)
 	}
 
 	remainingPaths := paths[1:]
 	for _, child := range children {
-		child.Value = UpdatedChildValue(child.Value, remainingPaths, value)
+		child.Value = n.UpdatedChildValue(child.Value, remainingPaths, value)
 	}
-	log.Debugf("\tReturning mapSlice %v\n", mapSlice)
+	n.log.Debugf("\tReturning mapSlice %v\n", mapSlice)
 	return mapSlice
 }
 
-func UpdatedChildValue(child interface{}, remainingPaths []string, value interface{}) interface{} {
-	if len(remainingPaths) == 0 {
-		return value
-	}
-	log.Debugf("UpdatedChildValue for child %v with path %v to set value %v", child, remainingPaths, value)
-	log.Debugf("type of child is %v", reflect.TypeOf(child))
-
-	switch child := child.(type) {
-	case nil:
-		if remainingPaths[0] == "+" || remainingPaths[0] == "*" {
-			return writeArray(child, remainingPaths, value)
-		}
-	case []interface{}:
-		_, nextIndexErr := strconv.ParseInt(remainingPaths[0], 10, 64)
-		arrayCommand := nextIndexErr == nil || remainingPaths[0] == "+" || remainingPaths[0] == "*"
-		if arrayCommand {
-			return writeArray(child, remainingPaths, value)
-		}
-	}
-	return writeMap(child, remainingPaths, value)
-}
-
-func writeArray(context interface{}, paths []string, value interface{}) []interface{} {
-	log.Debugf("writeArray with path %v for %v to set value %v\n", paths, context, value)
-	array, _ := getArray(context)
+func (n *navigator) writeArray(context interface{}, paths []string, value interface{}) []interface{} {
+	n.log.Debugf("writeArray with path %v for %v to set value %v\n", paths, context, value)
+	array, _ := n.getArray(context)
 
 	if len(paths) == 0 {
 		return array
 	}
 
-	log.Debugf("\tarray %v\n", array)
+	n.log.Debugf("\tarray %v\n", array)
 
 	rawIndex := paths[0]
 	remainingPaths := paths[1:]
@@ -123,7 +188,7 @@ func writeArray(context interface{}, paths []string, value interface{}) []interf
 		index = int64(len(array))
 	} else if rawIndex == "*" {
 		for index, oldChild := range array {
-			array[index] = UpdatedChildValue(oldChild, remainingPaths, value)
+			array[index] = n.UpdatedChildValue(oldChild, remainingPaths, value)
 		}
 		return array
 	} else {
@@ -137,31 +202,31 @@ func writeArray(context interface{}, paths []string, value interface{}) []interf
 	}
 	currentChild := array[index]
 
-	log.Debugf("\tcurrentChild %v\n", currentChild)
+	n.log.Debugf("\tcurrentChild %v\n", currentChild)
 
-	array[index] = UpdatedChildValue(currentChild, remainingPaths, value)
-	log.Debugf("\tReturning array %v\n", array)
+	array[index] = n.UpdatedChildValue(currentChild, remainingPaths, value)
+	n.log.Debugf("\tReturning array %v\n", array)
 	return array
 }
 
-func readMap(context yaml.MapSlice, head string, tail []string) (interface{}, error) {
-	log.Debugf("readingMap %v with key %v\n", context, head)
+func (n *navigator) readMap(context yaml.MapSlice, head string, tail []string) (interface{}, error) {
+	n.log.Debugf("readingMap %v with key %v\n", context, head)
 	if head == "*" {
-		return readMapSplat(context, tail)
+		return n.readMapSplat(context, tail)
 	}
 
-	entries := entriesInSlice(context, head)
+	entries := n.entriesInSlice(context, head)
 	if len(entries) == 1 {
-		return calculateValue(entries[0].Value, tail)
+		return n.calculateValue(entries[0].Value, tail)
 	} else if len(entries) == 0 {
 		return nil, nil
 	}
 	var errInIdx error
 	values := make([]interface{}, len(entries))
 	for idx, entry := range entries {
-		values[idx], errInIdx = calculateValue(entry.Value, tail)
+		values[idx], errInIdx = n.calculateValue(entry.Value, tail)
 		if errInIdx != nil {
-			log.Errorf("Error updating index %v in %v", idx, context)
+			n.log.Errorf("Error updating index %v in %v", idx, context)
 			return nil, errInIdx
 		}
 
@@ -169,12 +234,12 @@ func readMap(context yaml.MapSlice, head string, tail []string) (interface{}, er
 	return values, nil
 }
 
-func readMapSplat(context yaml.MapSlice, tail []string) (interface{}, error) {
+func (n *navigator) readMapSplat(context yaml.MapSlice, tail []string) (interface{}, error) {
 	var newArray = make([]interface{}, len(context))
 	var i = 0
 	for _, entry := range context {
 		if len(tail) > 0 {
-			val, err := Recurse(entry.Value, tail[0], tail[1:])
+			val, err := n.recurse(entry.Value, tail[0], tail[1:])
 			if err != nil {
 				return nil, err
 			}
@@ -187,37 +252,19 @@ func readMapSplat(context yaml.MapSlice, tail []string) (interface{}, error) {
 	return newArray, nil
 }
 
-func Recurse(value interface{}, head string, tail []string) (interface{}, error) {
-	switch value := value.(type) {
-	case []interface{}:
-		if head == "*" {
-			return readArraySplat(value, tail)
-		}
-		index, err := strconv.ParseInt(head, 10, 64)
-		if err != nil {
-			return nil, fmt.Errorf("error accessing array: %v", err)
-		}
-		return readArray(value, index, tail)
-	case yaml.MapSlice:
-		return readMap(value, head, tail)
-	default:
-		return nil, nil
-	}
-}
-
-func readArray(array []interface{}, head int64, tail []string) (interface{}, error) {
+func (n *navigator) readArray(array []interface{}, head int64, tail []string) (interface{}, error) {
 	if head >= int64(len(array)) {
 		return nil, nil
 	}
 
 	value := array[head]
-	return calculateValue(value, tail)
+	return n.calculateValue(value, tail)
 }
 
-func readArraySplat(array []interface{}, tail []string) (interface{}, error) {
+func (n *navigator) readArraySplat(array []interface{}, tail []string) (interface{}, error) {
 	var newArray = make([]interface{}, len(array))
 	for index, value := range array {
-		val, err := calculateValue(value, tail)
+		val, err := n.calculateValue(value, tail)
 		if err != nil {
 			return nil, err
 		}
@@ -226,17 +273,17 @@ func readArraySplat(array []interface{}, tail []string) (interface{}, error) {
 	return newArray, nil
 }
 
-func calculateValue(value interface{}, tail []string) (interface{}, error) {
+func (n *navigator) calculateValue(value interface{}, tail []string) (interface{}, error) {
 	if len(tail) > 0 {
-		return Recurse(value, tail[0], tail[1:])
+		return n.recurse(value, tail[0], tail[1:])
 	}
 	return value, nil
 }
 
-func deleteMap(context interface{}, paths []string) (yaml.MapSlice, error) {
-	log.Debugf("deleteMap for %v for %v\n", paths, context)
+func (n *navigator) deleteMap(context interface{}, paths []string) (yaml.MapSlice, error) {
+	n.log.Debugf("deleteMap for %v for %v\n", paths, context)
 
-	mapSlice := getMapSlice(context)
+	mapSlice := n.getMapSlice(context)
 
 	if len(paths) == 0 {
 		return mapSlice, nil
@@ -245,10 +292,10 @@ func deleteMap(context interface{}, paths []string) (yaml.MapSlice, error) {
 	var index int
 	var child yaml.MapItem
 	for index, child = range mapSlice {
-		if matchesKey(paths[0], child.Key) {
-			log.Debugf("\tMatched [%v] with [%v] at index %v", paths[0], child.Key, index)
+		if n.matchesKey(paths[0], child.Key) {
+			n.log.Debugf("\tMatched [%v] with [%v] at index %v", paths[0], child.Key, index)
 			var badDelete error
-			mapSlice, badDelete = deleteEntryInMap(mapSlice, child, index, paths)
+			mapSlice, badDelete = n.deleteEntryInMap(mapSlice, child, index, paths)
 			if badDelete != nil {
 				return nil, badDelete
 			}
@@ -259,14 +306,14 @@ func deleteMap(context interface{}, paths []string) (yaml.MapSlice, error) {
 
 }
 
-func deleteEntryInMap(original yaml.MapSlice, child yaml.MapItem, index int, paths []string) (yaml.MapSlice, error) {
+func (n *navigator) deleteEntryInMap(original yaml.MapSlice, child yaml.MapItem, index int, paths []string) (yaml.MapSlice, error) {
 	remainingPaths := paths[1:]
 
 	var newSlice yaml.MapSlice
 	if len(remainingPaths) > 0 {
 		newChild := yaml.MapItem{Key: child.Key}
 		var errorDeleting error
-		newChild.Value, errorDeleting = DeleteChildValue(child.Value, remainingPaths)
+		newChild.Value, errorDeleting = n.DeleteChildValue(child.Value, remainingPaths)
 		if errorDeleting != nil {
 			return nil, errorDeleting
 		}
@@ -282,18 +329,18 @@ func deleteEntryInMap(original yaml.MapSlice, child yaml.MapItem, index int, pat
 	} else {
 		// Delete item from slice at index
 		newSlice = append(original[:index], original[index+1:]...)
-		log.Debugf("\tDeleted item index %d from original", index)
+		n.log.Debugf("\tDeleted item index %d from original", index)
 	}
 
-	log.Debugf("\tReturning original %v\n", original)
+	n.log.Debugf("\tReturning original %v\n", original)
 	return newSlice, nil
 }
 
-func deleteArraySplat(array []interface{}, tail []string) (interface{}, error) {
-	log.Debugf("deleteArraySplat for %v for %v\n", tail, array)
+func (n *navigator) deleteArraySplat(array []interface{}, tail []string) (interface{}, error) {
+	n.log.Debugf("deleteArraySplat for %v for %v\n", tail, array)
 	var newArray = make([]interface{}, len(array))
 	for index, value := range array {
-		val, err := DeleteChildValue(value, tail)
+		val, err := n.DeleteChildValue(value, tail)
 		if err != nil {
 			return nil, err
 		}
@@ -302,8 +349,8 @@ func deleteArraySplat(array []interface{}, tail []string) (interface{}, error) {
 	return newArray, nil
 }
 
-func deleteArray(array []interface{}, paths []string, index int64) (interface{}, error) {
-	log.Debugf("deleteArray for %v for %v\n", paths, array)
+func (n *navigator) deleteArray(array []interface{}, paths []string, index int64) (interface{}, error) {
+	n.log.Debugf("deleteArray for %v for %v\n", paths, array)
 
 	if index >= int64(len(array)) {
 		return array, nil
@@ -311,9 +358,9 @@ func deleteArray(array []interface{}, paths []string, index int64) (interface{},
 
 	remainingPaths := paths[1:]
 	if len(remainingPaths) > 0 {
-		// Recurse into the array element at index
+		// recurse into the array element at index
 		var errorDeleting error
-		array[index], errorDeleting = deleteMap(array[index], remainingPaths)
+		array[index], errorDeleting = n.deleteMap(array[index], remainingPaths)
 		if errorDeleting != nil {
 			return nil, errorDeleting
 		}
@@ -321,29 +368,9 @@ func deleteArray(array []interface{}, paths []string, index int64) (interface{},
 	} else {
 		// Delete the array element at index
 		array = append(array[:index], array[index+1:]...)
-		log.Debugf("\tDeleted item index %d from array, leaving %v", index, array)
+		n.log.Debugf("\tDeleted item index %d from array, leaving %v", index, array)
 	}
 
-	log.Debugf("\tReturning array: %v\n", array)
+	n.log.Debugf("\tReturning array: %v\n", array)
 	return array, nil
 }
-
-func DeleteChildValue(child interface{}, remainingPaths []string) (interface{}, error) {
-	log.Debugf("DeleteChildValue for %v for %v\n", remainingPaths, child)
-	var head = remainingPaths[0]
-	var tail = remainingPaths[1:]
-	switch child := child.(type) {
-	case yaml.MapSlice:
-		return deleteMap(child, remainingPaths)
-	case []interface{}:
-		if head == "*" {
-			return deleteArraySplat(child, tail)
-		}
-		index, err := strconv.ParseInt(head, 10, 64)
-		if err != nil {
-			return nil, fmt.Errorf("error accessing array: %v", err)
-		}
-		return deleteArray(child, remainingPaths, index)
-	}
-	return child, nil
-}
diff --git a/pkg/yqlib/data_navigator_test.go b/pkg/yqlib/data_navigator_test.go
index ff772e1..439ff73 100644
--- a/pkg/yqlib/data_navigator_test.go
+++ b/pkg/yqlib/data_navigator_test.go
@@ -5,53 +5,58 @@ import (
 	"sort"
 	"testing"
 	"github.com/mikefarah/yq/test"
+	logging "gopkg.in/op/go-logging.v1"
 )
 
-func TestReadMap_simple(t *testing.T) {
-	var data = test.ParseData(`
+func TestDataNavigator(t *testing.T) {
+	var log = logging.MustGetLogger("yq")
+	subject := NewDataNavigator(log)
+
+	t.Run("TestReadMap_simple", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   c: 2
 `)
-	got, _ := readMap(data, "b", []string{"c"})
-	test.AssertResult(t, 2, got)
-}
+		got, _ := subject.ReadChildValue(data, []string{"b", "c"})
+		test.AssertResult(t, 2, got)
+	})
 
-func TestReadMap_numberKey(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestReadMap_numberKey", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 200: things
 `)
-	got, _ := readMap(data, "200", []string{})
-	test.AssertResult(t, "things", got)
-}
+		got, _ := subject.ReadChildValue(data, []string{"200"})
+		test.AssertResult(t, "things", got)
+	})
 
-func TestReadMap_splat(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestReadMap_splat", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 mapSplat:
   item1: things
   item2: whatever
   otherThing: cat
 `)
-	res, _ := readMap(data, "mapSplat", []string{"*"})
-	test.AssertResult(t, "[things whatever cat]", fmt.Sprintf("%v", res))
-}
+		res, _ := subject.ReadChildValue(data, []string{"mapSplat", "*"})
+		test.AssertResult(t, "[things whatever cat]", fmt.Sprintf("%v", res))
+	})
 
-func TestReadMap_prefixSplat(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestReadMap_prefixSplat", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 mapSplat:
   item1: things
   item2: whatever
   otherThing: cat
 `)
-	res, _ := readMap(data, "mapSplat", []string{"item*"})
-	test.AssertResult(t, "[things whatever]", fmt.Sprintf("%v", res))
-}
+		res, _ := subject.ReadChildValue(data, []string{"mapSplat", "item*"})
+		test.AssertResult(t, "[things whatever]", fmt.Sprintf("%v", res))
+	})
 
-func TestReadMap_deep_splat(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestReadMap_deep_splat", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 mapSplatDeep:
   item1:
@@ -60,62 +65,62 @@ mapSplatDeep:
     cats: apples
 `)
 
-	res, _ := readMap(data, "mapSplatDeep", []string{"*", "cats"})
-	result := res.([]interface{})
-	var actual = []string{result[0].(string), result[1].(string)}
-	sort.Strings(actual)
-	test.AssertResult(t, "[apples bananas]", fmt.Sprintf("%v", actual))
-}
+		res, _ := subject.ReadChildValue(data, []string{"mapSplatDeep", "*", "cats"})
+		result := res.([]interface{})
+		var actual = []string{result[0].(string), result[1].(string)}
+		sort.Strings(actual)
+		test.AssertResult(t, "[apples bananas]", fmt.Sprintf("%v", actual))
+	})
 
-func TestReadMap_key_doesnt_exist(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestReadMap_key_doesnt_exist", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   c: 2
 `)
-	got, _ := readMap(data, "b.x.f", []string{"c"})
-	test.AssertResult(t, nil, got)
-}
+		got, _ := subject.ReadChildValue(data, []string{"b", "x", "f", "c"})
+		test.AssertResult(t, nil, got)
+	})
 
-func TestReadMap_recurse_against_string(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestReadMap_recurse_against_string", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 a: cat
 `)
-	got, _ := readMap(data, "a", []string{"b"})
-	test.AssertResult(t, nil, got)
-}
+		got, _ := subject.ReadChildValue(data, []string{"a", "b"})
+		test.AssertResult(t, nil, got)
+	})
 
-func TestReadMap_with_array(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestReadMap_with_array", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   d:
     - 3
     - 4
 `)
-	got, _ := readMap(data, "b", []string{"d", "1"})
-	test.AssertResult(t, 4, got)
-}
+		got, _ := subject.ReadChildValue(data, []string{"b", "d", "1"})
+		test.AssertResult(t, 4, got)
+	})
 
-func TestReadMap_with_array_and_bad_index(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestReadMap_with_array_and_bad_index", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   d:
     - 3
     - 4
 `)
-	_, err := readMap(data, "b", []string{"d", "x"})
-	if err == nil {
-		t.Fatal("Expected error due to invalid path")
-	}
-	expectedOutput := `error accessing array: strconv.ParseInt: parsing "x": invalid syntax`
-	test.AssertResult(t, expectedOutput, err.Error())
-}
+		_, err := subject.ReadChildValue(data, []string{"b", "d", "x"})
+		if err == nil {
+			t.Fatal("Expected error due to invalid path")
+		}
+		expectedOutput := `error accessing array: strconv.ParseInt: parsing "x": invalid syntax`
+		test.AssertResult(t, expectedOutput, err.Error())
+	})
 
-func TestReadMap_with_mapsplat_array_and_bad_index(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestReadMap_with_mapsplat_array_and_bad_index", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   d:
@@ -126,16 +131,16 @@ b:
       - 1
       - 2
 `)
-	_, err := readMap(data, "b", []string{"d", "*", "x"})
-	if err == nil {
-		t.Fatal("Expected error due to invalid path")
-	}
-	expectedOutput := `error accessing array: strconv.ParseInt: parsing "x": invalid syntax`
-	test.AssertResult(t, expectedOutput, err.Error())
-}
+		_, err := subject.ReadChildValue(data, []string{"b", "d", "*", "x"})
+		if err == nil {
+			t.Fatal("Expected error due to invalid path")
+		}
+		expectedOutput := `error accessing array: strconv.ParseInt: parsing "x": invalid syntax`
+		test.AssertResult(t, expectedOutput, err.Error())
+	})
 
-func TestReadMap_with_arraysplat_map_array_and_bad_index(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestReadMap_with_arraysplat_map_array_and_bad_index", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   d:
@@ -146,40 +151,40 @@ b:
         - sam
         - bo
 `)
-	_, err := readMap(data, "b", []string{"d", "*", "names", "x"})
-	if err == nil {
-		t.Fatal("Expected error due to invalid path")
-	}
-	expectedOutput := `error accessing array: strconv.ParseInt: parsing "x": invalid syntax`
-	test.AssertResult(t, expectedOutput, err.Error())
-}
+		_, err := subject.ReadChildValue(data, []string{"b", "d", "*", "names", "x"})
+		if err == nil {
+			t.Fatal("Expected error due to invalid path")
+		}
+		expectedOutput := `error accessing array: strconv.ParseInt: parsing "x": invalid syntax`
+		test.AssertResult(t, expectedOutput, err.Error())
+	})
 
-func TestReadMap_with_array_out_of_bounds(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestReadMap_with_array_out_of_bounds", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   d:
     - 3
     - 4
 `)
-	got, _ := readMap(data, "b", []string{"d", "3"})
-	test.AssertResult(t, nil, got)
-}
+		got, _ := subject.ReadChildValue(data, []string{"b", "d", "3"})
+		test.AssertResult(t, nil, got)
+	})
 
-func TestReadMap_with_array_out_of_bounds_by_1(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestReadMap_with_array_out_of_bounds_by_1", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   d:
     - 3
     - 4
 `)
-	got, _ := readMap(data, "b", []string{"d", "2"})
-	test.AssertResult(t, nil, got)
-}
+		got, _ := subject.ReadChildValue(data, []string{"b", "d", "2"})
+		test.AssertResult(t, nil, got)
+	})
 
-func TestReadMap_with_array_splat(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestReadMap_with_array_splat", func(t *testing.T) {
+		var data = test.ParseData(`
 e:
   -
     name: Fred
@@ -188,213 +193,204 @@ e:
     name: Sam
     thing: dog
 `)
-	got, _ := readMap(data, "e", []string{"*", "name"})
-	test.AssertResult(t, "[Fred Sam]", fmt.Sprintf("%v", got))
-}
+		got, _ := subject.ReadChildValue(data, []string{"e", "*", "name"})
+		test.AssertResult(t, "[Fred Sam]", fmt.Sprintf("%v", got))
+	})
 
-func TestWrite_really_simple(t *testing.T) {
-	var data = test.ParseData(`
-    b: 2
+	t.Run("TestWrite_really_simple", func(t *testing.T) {
+		var data = test.ParseData(`
+b: 2
 `)
 
-	updated := writeMap(data, []string{"b"}, "4")
-	test.AssertResult(t, "[{b 4}]", fmt.Sprintf("%v", updated))
-}
+		updated := subject.UpdatedChildValue(data, []string{"b"}, "4")
+		test.AssertResult(t, "[{b 4}]", fmt.Sprintf("%v", updated))
+	})
 
-func TestWrite_simple(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestWrite_simple", func(t *testing.T) {
+		var data = test.ParseData(`
 b:
   c: 2
 `)
 
-	updated := writeMap(data, []string{"b", "c"}, "4")
-	test.AssertResult(t, "[{b [{c 4}]}]", fmt.Sprintf("%v", updated))
-}
+		updated := subject.UpdatedChildValue(data, []string{"b", "c"}, "4")
+		test.AssertResult(t, "[{b [{c 4}]}]", fmt.Sprintf("%v", updated))
+	})
 
-func TestWrite_new(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestWrite_new", func(t *testing.T) {
+		var data = test.ParseData(`
 b:
   c: 2
 `)
 
-	updated := writeMap(data, []string{"b", "d"}, "4")
-	test.AssertResult(t, "[{b [{c 2} {d 4}]}]", fmt.Sprintf("%v", updated))
-}
+		updated := subject.UpdatedChildValue(data, []string{"b", "d"}, "4")
+		test.AssertResult(t, "[{b [{c 2} {d 4}]}]", fmt.Sprintf("%v", updated))
+	})
 
-func TestWrite_new_deep(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestWrite_new_deep", func(t *testing.T) {
+		var data = test.ParseData(`
 b:
   c: 2
 `)
 
-	updated := writeMap(data, []string{"b", "d", "f"}, "4")
-	test.AssertResult(t, "[{b [{c 2} {d [{f 4}]}]}]", fmt.Sprintf("%v", updated))
-}
+		updated := subject.UpdatedChildValue(data, []string{"b", "d", "f"}, "4")
+		test.AssertResult(t, "[{b [{c 2} {d [{f 4}]}]}]", fmt.Sprintf("%v", updated))
+	})
 
-func TestWrite_array(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestWrite_array", func(t *testing.T) {
+		var data = test.ParseData(`
 b:
   - aa
 `)
 
-	updated := writeMap(data, []string{"b", "0"}, "bb")
+		updated := subject.UpdatedChildValue(data, []string{"b", "0"}, "bb")
 
-	test.AssertResult(t, "[{b [bb]}]", fmt.Sprintf("%v", updated))
-}
+		test.AssertResult(t, "[{b [bb]}]", fmt.Sprintf("%v", updated))
+	})
 
-func TestWrite_new_array(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestWrite_new_array", func(t *testing.T) {
+		var data = test.ParseData(`
 b:
   c: 2
 `)
 
-	updated := writeMap(data, []string{"b", "0"}, "4")
-	test.AssertResult(t, "[{b [{c 2} {0 4}]}]", fmt.Sprintf("%v", updated))
-}
+		updated := subject.UpdatedChildValue(data, []string{"b", "0"}, "4")
+		test.AssertResult(t, "[{b [{c 2} {0 4}]}]", fmt.Sprintf("%v", updated))
+	})
 
-func TestWrite_new_array_deep(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestWrite_new_array_deep", func(t *testing.T) {
+		var data = test.ParseData(`
 a: apple
 `)
 
-	var expected = `a: apple
-b:
-- c: "4"`
+		updated := subject.UpdatedChildValue(data, []string{"b", "+", "c"}, "4")
+		test.AssertResult(t, "[{a apple} {b [[{c 4}]]}]", fmt.Sprintf("%v", updated))
+	})
 
-	updated := writeMap(data, []string{"b", "+", "c"}, "4")
-	got, _ := YamlToString(updated, true)
-	test.AssertResult(t, expected, got)
-}
-
-func TestWrite_new_map_array_deep(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestWrite_new_map_array_deep", func(t *testing.T) {
+		var data = test.ParseData(`
 b:
   c: 2
 `)
-	var expected = `b:
-  c: 2
-  d:
-  - "4"`
 
-	updated := writeMap(data, []string{"b", "d", "+"}, "4")
-	got, _ := YamlToString(updated, true)
-	test.AssertResult(t, expected, got)
-}
+		updated := subject.UpdatedChildValue(data, []string{"b", "d", "+"}, "4")
+		test.AssertResult(t, "[{b [{c 2} {d [4]}]}]", fmt.Sprintf("%v", updated))
+	})
 
-func TestWrite_add_to_array(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestWrite_add_to_array", func(t *testing.T) {
+		var data = test.ParseData(`
 b:
   - aa
 `)
 
-	var expected = `b:
-- aa
-- bb`
+		updated := subject.UpdatedChildValue(data, []string{"b", "1"}, "bb")
+		test.AssertResult(t, "[{b [aa bb]}]", fmt.Sprintf("%v", updated))
+	})
 
-	updated := writeMap(data, []string{"b", "1"}, "bb")
-	got, _ := YamlToString(updated, true)
-	test.AssertResult(t, expected, got)
-}
-
-func TestWrite_with_no_tail(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestWrite_with_no_tail", func(t *testing.T) {
+		var data = test.ParseData(`
 b:
   c: 2
 `)
-	updated := writeMap(data, []string{"b"}, "4")
+		updated := subject.UpdatedChildValue(data, []string{"b"}, "4")
 
-	test.AssertResult(t, "[{b 4}]", fmt.Sprintf("%v", updated))
-}
+		test.AssertResult(t, "[{b 4}]", fmt.Sprintf("%v", updated))
+	})
 
-func TestWriteMap_no_paths(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestWriteMap_no_paths", func(t *testing.T) {
+		var data = test.ParseData(`
 b: 5
 `)
+		var new = test.ParseData(`
+c: 4
+`)
+		result := subject.UpdatedChildValue(data, []string{}, new)
+		test.AssertResult(t, fmt.Sprintf("%v", new), fmt.Sprintf("%v", result))
+	})
 
-	result := writeMap(data, []string{}, 4)
-	test.AssertResult(t, fmt.Sprintf("%v", data), fmt.Sprintf("%v", result))
-}
+	t.Run("TestWriteArray_no_paths", func(t *testing.T) {
+		var data = make([]interface{}, 1)
+		data[0] = "mike"
+		var new = test.ParseData(`
+c: 4
+`)
+		result := subject.UpdatedChildValue(data, []string{}, new)
+		test.AssertResult(t, fmt.Sprintf("%v", new), fmt.Sprintf("%v", result))
+	})
 
-func TestWriteArray_no_paths(t *testing.T) {
-	var data = make([]interface{}, 1)
-	data[0] = "mike"
-	result := writeArray(data, []string{}, 4)
-	test.AssertResult(t, fmt.Sprintf("%v", data), fmt.Sprintf("%v", result))
-}
-
-func TestDelete_MapItem(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestDelete_MapItem", func(t *testing.T) {
+		var data = test.ParseData(`
 a: 123
 b: 456
 `)
-	var expected = test.ParseData(`
+		var expected = test.ParseData(`
 b: 456
 `)
 
-	result, _ := deleteMap(data, []string{"a"})
-	test.AssertResult(t, fmt.Sprintf("%v", expected), fmt.Sprintf("%v", result))
-}
+		result, _ := subject.DeleteChildValue(data, []string{"a"})
+		test.AssertResult(t, fmt.Sprintf("%v", expected), fmt.Sprintf("%v", result))
+	})
 
-// Ensure deleting an index into a string does nothing
-func TestDelete_index_to_string(t *testing.T) {
-	var data = test.ParseData(`
+	// Ensure deleting an index into a string does nothing
+	t.Run("TestDelete_index_to_string", func(t *testing.T) {
+		var data = test.ParseData(`
 a: mystring
 `)
-	result, _ := deleteMap(data, []string{"a", "0"})
-	test.AssertResult(t, fmt.Sprintf("%v", data), fmt.Sprintf("%v", result))
-}
+		result, _ := subject.DeleteChildValue(data, []string{"a", "0"})
+		test.AssertResult(t, fmt.Sprintf("%v", data), fmt.Sprintf("%v", result))
+	})
 
-func TestDelete_list_index(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestDelete_list_index", func(t *testing.T) {
+		var data = test.ParseData(`
 a: [3, 4]
 `)
-	var expected = test.ParseData(`
+		var expected = test.ParseData(`
 a: [3]
 `)
-	result, _ := deleteMap(data, []string{"a", "1"})
-	test.AssertResult(t, fmt.Sprintf("%v", expected), fmt.Sprintf("%v", result))
-}
+		result, _ := subject.DeleteChildValue(data, []string{"a", "1"})
+		test.AssertResult(t, fmt.Sprintf("%v", expected), fmt.Sprintf("%v", result))
+	})
 
-func TestDelete_list_index_beyond_bounds(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestDelete_list_index_beyond_bounds", func(t *testing.T) {
+		var data = test.ParseData(`
 a: [3, 4]
 `)
-	result, _ := deleteMap(data, []string{"a", "5"})
-	test.AssertResult(t, fmt.Sprintf("%v", data), fmt.Sprintf("%v", result))
-}
+		result, _ := subject.DeleteChildValue(data, []string{"a", "5"})
+		test.AssertResult(t, fmt.Sprintf("%v", data), fmt.Sprintf("%v", result))
+	})
 
-func TestDelete_list_index_out_of_bounds_by_1(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestDelete_list_index_out_of_bounds_by_1", func(t *testing.T) {
+		var data = test.ParseData(`
 a: [3, 4]
 `)
-	result, _ := deleteMap(data, []string{"a", "2"})
-	test.AssertResult(t, fmt.Sprintf("%v", data), fmt.Sprintf("%v", result))
-}
+		result, _ := subject.DeleteChildValue(data, []string{"a", "2"})
+		test.AssertResult(t, fmt.Sprintf("%v", data), fmt.Sprintf("%v", result))
+	})
 
-func TestDelete_no_paths(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestDelete_no_paths", func(t *testing.T) {
+		var data = test.ParseData(`
 a: [3, 4]
 b:
   - name: test
 `)
-	result, _ := deleteMap(data, []string{})
-	test.AssertResult(t, fmt.Sprintf("%v", data), fmt.Sprintf("%v", result))
-}
+		result, _ := subject.DeleteChildValue(data, []string{})
+		test.AssertResult(t, fmt.Sprintf("%v", data), fmt.Sprintf("%v", result))
+	})
 
-func TestDelete_array_map_item(t *testing.T) {
-	var data = test.ParseData(`
+	t.Run("TestDelete_array_map_item", func(t *testing.T) {
+		var data = test.ParseData(`
 b:
 - name: fred
   value: blah
 - name: john
   value: test
 `)
-	var expected = test.ParseData(`
+		var expected = test.ParseData(`
 b:
 - value: blah
 - name: john
   value: test
 `)
-	result, _ := deleteMap(data, []string{"b", "0", "name"})
-	test.AssertResult(t, fmt.Sprintf("%v", expected), fmt.Sprintf("%v", result))
-}
+		result, _ := subject.DeleteChildValue(data, []string{"b", "0", "name"})
+		test.AssertResult(t, fmt.Sprintf("%v", expected), fmt.Sprintf("%v", result))
+	})
+}
\ No newline at end of file
diff --git a/pkg/yqlib/lib.go b/pkg/yqlib/lib.go
index fe3a986..eb4f350 100644
--- a/pkg/yqlib/lib.go
+++ b/pkg/yqlib/lib.go
@@ -5,24 +5,38 @@ import (
 	logging "gopkg.in/op/go-logging.v1"
 )
 
-var log = logging.MustGetLogger("yq")
-
-func SetLogger(l *logging.Logger) {
-	log = l
+type YqLib interface {
+	ReadPath(dataBucket interface{}, path string) (interface{}, error)
+	WritePath(dataBucket interface{}, path string, value interface{}) (interface{})
+	PrefixPath(dataBucket interface{}, prefix string) (interface{})
+	DeletePath(dataBucket interface{}, path string) (interface{}, error)
+	Merge(dst interface{}, src interface{}, overwrite bool, append bool) error
 }
 
-func ReadPath(dataBucket interface{}, path string) (interface{}, error) {
-	var paths = ParsePath(path)
-	return Recurse(dataBucket, paths[0], paths[1:])
+type lib struct {
+	navigator DataNavigator
+	parser PathParser
 }
 
-func WritePath(dataBucket interface{}, path string, value interface{}) (interface{}) {
-	var paths = ParsePath(path)
-	return UpdatedChildValue(dataBucket, paths, value)
+func NewYqLib(l *logging.Logger) YqLib {
+	return &lib {
+		navigator: NewDataNavigator(l),
+		parser: NewPathParser(),
+	}
 }
 
-func PrefixPath(dataBucket interface{}, prefix string) (interface{}) {
-	var paths = ParsePath(prefix)
+func (l *lib) ReadPath(dataBucket interface{}, path string) (interface{}, error) {
+	var paths = l.parser.ParsePath(path)
+	return l.navigator.ReadChildValue(dataBucket, paths)
+}
+
+func (l *lib) WritePath(dataBucket interface{}, path string, value interface{}) (interface{}) {
+	var paths = l.parser.ParsePath(path)
+	return l.navigator.UpdatedChildValue(dataBucket, paths, value)
+}
+
+func (l *lib) PrefixPath(dataBucket interface{}, prefix string) (interface{}) {
+	var paths = l.parser.ParsePath(prefix)
 
 	// Inverse order
 	for i := len(paths)/2 - 1; i >= 0; i-- {
@@ -33,18 +47,18 @@ func PrefixPath(dataBucket interface{}, prefix string) (interface{}) {
 	var mapDataBucket = dataBucket
 	for _, key := range paths {
 		singlePath := []string{key}
-		mapDataBucket = UpdatedChildValue(nil, singlePath, mapDataBucket)
+		mapDataBucket = l.navigator.UpdatedChildValue(nil, singlePath, mapDataBucket)
 	}
 
 	return mapDataBucket
 }
 
-func DeletePath(dataBucket interface{}, path string) (interface{}, error) {
-	var paths = ParsePath(path)
-	return DeleteChildValue(dataBucket, paths)
+func (l *lib) DeletePath(dataBucket interface{}, path string) (interface{}, error) {
+	var paths = l.parser.ParsePath(path)
+	return l.navigator.DeleteChildValue(dataBucket, paths)
 }
 
-func Merge(dst interface{}, src interface{}, overwrite bool, append bool) error {
+func (l *lib) Merge(dst interface{}, src interface{}, overwrite bool, append bool) error {
 	if overwrite {
 		return mergo.Merge(dst, src, mergo.WithOverride)
 	} else if append {
diff --git a/pkg/yqlib/lib_test.go b/pkg/yqlib/lib_test.go
index f0511f1..6eba4fc 100644
--- a/pkg/yqlib/lib_test.go
+++ b/pkg/yqlib/lib_test.go
@@ -4,145 +4,153 @@ import (
 	"fmt"
 	"testing"
 	"github.com/mikefarah/yq/test"
+	logging "gopkg.in/op/go-logging.v1"
 )
 
-func TestReadPath(t *testing.T) {
-	var data = test.ParseData(`
+func TestLib(t *testing.T) {
+
+	var log = logging.MustGetLogger("yq")
+	subject := NewYqLib(log)
+
+	t.Run("TestReadPath", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   2: c
 `)
-
-	got, _ := ReadPath(data, "b.2")
-	test.AssertResult(t, `c`, got)
-}
-
-func TestReadPath_WithError(t *testing.T) {
-	var data = test.ParseData(`
+	
+		got, _ := subject.ReadPath(data, "b.2")
+		test.AssertResult(t, `c`, got)
+	})
+	
+	t.Run("TestReadPath_WithError", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   - c
 `)
-
-	_, err := ReadPath(data, "b.[a]")
-	if err == nil {
-		t.Fatal("Expected error due to invalid path")
-	}
-}
-
-func TestWritePath(t *testing.T) {
-	var data = test.ParseData(`
+	
+		_, err := subject.ReadPath(data, "b.[a]")
+		if err == nil {
+			t.Fatal("Expected error due to invalid path")
+		}
+	})
+	
+	t.Run("TestWritePath", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   2: c
 `)
-
-	got := WritePath(data, "b.3", "a")
-	test.AssertResult(t, `[{b [{2 c} {3 a}]}]`, fmt.Sprintf("%v", got))
-}
-
-func TestPrefixPath(t *testing.T) {
-	var data = test.ParseData(`
+	
+		got := subject.WritePath(data, "b.3", "a")
+		test.AssertResult(t, `[{b [{2 c} {3 a}]}]`, fmt.Sprintf("%v", got))
+	})
+	
+	t.Run("TestPrefixPath", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   2: c
 `)
-
-	got := PrefixPath(data, "d")
-	test.AssertResult(t, `[{d [{b [{2 c}]}]}]`, fmt.Sprintf("%v", got))
-}
-
-func TestDeletePath(t *testing.T) {
-	var data = test.ParseData(`
+	
+		got := subject.PrefixPath(data, "d")
+		test.AssertResult(t, `[{d [{b [{2 c}]}]}]`, fmt.Sprintf("%v", got))
+	})
+	
+	t.Run("TestDeletePath", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   2: c
   3: a
 `)
-
-	got, _ := DeletePath(data, "b.2")
-	test.AssertResult(t, `[{b [{3 a}]}]`, fmt.Sprintf("%v", got))
-}
-
-func TestDeletePath_WithError(t *testing.T) {
-	var data = test.ParseData(`
+	
+		got, _ := subject.DeletePath(data, "b.2")
+		test.AssertResult(t, `[{b [{3 a}]}]`, fmt.Sprintf("%v", got))
+	})
+	
+	t.Run("TestDeletePath_WithError", func(t *testing.T) {
+		var data = test.ParseData(`
 ---
 b:
   - c
 `)
-
-	_, err := DeletePath(data, "b.[a]")
-	if err == nil {
-		t.Fatal("Expected error due to invalid path")
-	}
-}
-
-func TestMerge(t *testing.T) {
-	var dst = test.ParseData(`
+	
+		_, err := subject.DeletePath(data, "b.[a]")
+		if err == nil {
+			t.Fatal("Expected error due to invalid path")
+		}
+	})
+	
+	t.Run("TestMerge", func(t *testing.T) {
+		var dst = test.ParseData(`
 ---
 a: b
 c: d
 `)
-	var src = test.ParseData(`
+		var src = test.ParseData(`
 ---
 a: 1
 b: 2
 `)
-
-	var mergedData = make(map[interface{}]interface{})
-	mergedData["root"] = dst
-	var mapDataBucket = make(map[interface{}]interface{})
-	mapDataBucket["root"] = src
-
-	Merge(&mergedData, mapDataBucket, false, false)
-	test.AssertResult(t, `[{a b} {c d}]`, fmt.Sprintf("%v", mergedData["root"]))
-}
-
-func TestMerge_WithOverwrite(t *testing.T) {
-	var dst = test.ParseData(`
+	
+		var mergedData = make(map[interface{}]interface{})
+		mergedData["root"] = dst
+		var mapDataBucket = make(map[interface{}]interface{})
+		mapDataBucket["root"] = src
+	
+		subject.Merge(&mergedData, mapDataBucket, false, false)
+		test.AssertResult(t, `[{a b} {c d}]`, fmt.Sprintf("%v", mergedData["root"]))
+	})
+	
+	t.Run("TestMerge_WithOverwrite", func(t *testing.T) {
+		var dst = test.ParseData(`
 ---
 a: b
 c: d
 `)
-	var src = test.ParseData(`
+		var src = test.ParseData(`
 ---
 a: 1
 b: 2
 `)
-
-	var mergedData = make(map[interface{}]interface{})
-	mergedData["root"] = dst
-	var mapDataBucket = make(map[interface{}]interface{})
-	mapDataBucket["root"] = src
-
-	Merge(&mergedData, mapDataBucket, true, false)
-	test.AssertResult(t, `[{a 1} {b 2}]`, fmt.Sprintf("%v", mergedData["root"]))
-}
-
-func TestMerge_WithAppend(t *testing.T) {
-	var dst = test.ParseData(`
+	
+		var mergedData = make(map[interface{}]interface{})
+		mergedData["root"] = dst
+		var mapDataBucket = make(map[interface{}]interface{})
+		mapDataBucket["root"] = src
+	
+		subject.Merge(&mergedData, mapDataBucket, true, false)
+		test.AssertResult(t, `[{a 1} {b 2}]`, fmt.Sprintf("%v", mergedData["root"]))
+	})
+	
+	t.Run("TestMerge_WithAppend", func(t *testing.T) {
+		var dst = test.ParseData(`
 ---
 a: b
 c: d
 `)
-	var src = test.ParseData(`
+		var src = test.ParseData(`
 ---
 a: 1
 b: 2
 `)
+	
+		var mergedData = make(map[interface{}]interface{})
+		mergedData["root"] = dst
+		var mapDataBucket = make(map[interface{}]interface{})
+		mapDataBucket["root"] = src
+	
+		subject.Merge(&mergedData, mapDataBucket, false, true)
+		test.AssertResult(t, `[{a b} {c d} {a 1} {b 2}]`, fmt.Sprintf("%v", mergedData["root"]))
+	})
+	
+	t.Run("TestMerge_WithError", func(t *testing.T) {
+		err := subject.Merge(nil, nil, false, false)
+		if err == nil {
+			t.Fatal("Expected error due to nil")
+		}
+	})
 
-	var mergedData = make(map[interface{}]interface{})
-	mergedData["root"] = dst
-	var mapDataBucket = make(map[interface{}]interface{})
-	mapDataBucket["root"] = src
-
-	Merge(&mergedData, mapDataBucket, false, true)
-	test.AssertResult(t, `[{a b} {c d} {a 1} {b 2}]`, fmt.Sprintf("%v", mergedData["root"]))
-}
-
-func TestMerge_WithError(t *testing.T) {
-	err := Merge(nil, nil, false, false)
-	if err == nil {
-		t.Fatal("Expected error due to nil")
-	}
 }
\ No newline at end of file
diff --git a/pkg/yqlib/path_parser.go b/pkg/yqlib/path_parser.go
index a416b72..a1628ec 100644
--- a/pkg/yqlib/path_parser.go
+++ b/pkg/yqlib/path_parser.go
@@ -1,35 +1,45 @@
 package yqlib
 
-func ParsePath(path string) []string {
-	return parsePathAccum([]string{}, path)
+type PathParser interface {
+	ParsePath(path string) []string
 }
 
-func parsePathAccum(paths []string, remaining string) []string {
-	head, tail := nextYamlPath(remaining)
+type parser struct {}
+
+func NewPathParser() PathParser {
+	return &parser{}
+}
+
+func (p *parser) ParsePath(path string) []string {
+	return p.parsePathAccum([]string{}, path)
+}
+
+func (p *parser) parsePathAccum(paths []string, remaining string) []string {
+	head, tail := p.nextYamlPath(remaining)
 	if tail == "" {
 		return append(paths, head)
 	}
-	return parsePathAccum(append(paths, head), tail)
+	return p.parsePathAccum(append(paths, head), tail)
 }
 
-func nextYamlPath(path string) (pathElement string, remaining string) {
+func (p *parser) nextYamlPath(path string) (pathElement string, remaining string) {
 	switch path[0] {
 	case '[':
 		// e.g [0].blah.cat -> we need to return "0" and "blah.cat"
-		return search(path[1:], []uint8{']'}, true)
+		return p.search(path[1:], []uint8{']'}, true)
 	case '"':
 		// e.g "a.b".blah.cat -> we need to return "a.b" and "blah.cat"
-		return search(path[1:], []uint8{'"'}, true)
+		return p.search(path[1:], []uint8{'"'}, true)
 	default:
 		// e.g "a.blah.cat" -> return "a" and "blah.cat"
-		return search(path[0:], []uint8{'.', '['}, false)
+		return p.search(path[0:], []uint8{'.', '['}, false)
 	}
 }
 
-func search(path string, matchingChars []uint8, skipNext bool) (pathElement string, remaining string) {
+func (p *parser) search(path string, matchingChars []uint8, skipNext bool) (pathElement string, remaining string) {
 	for i := 0; i < len(path); i++ {
 		var char = path[i]
-		if contains(matchingChars, char) {
+		if p.contains(matchingChars, char) {
 			var remainingStart = i + 1
 			if skipNext {
 				remainingStart = remainingStart + 1
@@ -45,7 +55,7 @@ func search(path string, matchingChars []uint8, skipNext bool) (pathElement stri
 	return path, ""
 }
 
-func contains(matchingChars []uint8, candidate uint8) bool {
+func (p *parser) contains(matchingChars []uint8, candidate uint8) bool {
 	for _, a := range matchingChars {
 		if a == candidate {
 			return true
diff --git a/pkg/yqlib/path_parser_test.go b/pkg/yqlib/path_parser_test.go
index 7680aa8..000d214 100644
--- a/pkg/yqlib/path_parser_test.go
+++ b/pkg/yqlib/path_parser_test.go
@@ -12,33 +12,17 @@ var parsePathsTests = []struct {
 	{"a.b", []string{"a", "b"}},
 	{"a.b[0]", []string{"a", "b", "0"}},
 	{"a.b.d[+]", []string{"a", "b", "d", "+"}},
+	{"a", []string{"a"}},
+	{"a.b.c", []string{"a", "b", "c"}},
+	{"\"a.b\".c", []string{"a.b", "c"}},
+	{"a.\"b.c\".d", []string{"a", "b.c", "d"}},
+	{"[1].a.d", []string{"1", "a", "d"}},
+	{"a[0].c", []string{"a", "0", "c"}},
+	{"[0]", []string{"0"}},
 }
 
 func TestParsePath(t *testing.T) {
 	for _, tt := range parsePathsTests {
-		test.AssertResultComplex(t, tt.expectedPaths, ParsePath(tt.path))
+		test.AssertResultComplex(t, tt.expectedPaths, NewPathParser().ParsePath(tt.path))
 	}
-}
-
-var nextYamlPathTests = []struct {
-	path              string
-	expectedElement   string
-	expectedRemaining string
-}{
-	{"a.b", "a", "b"},
-	{"a", "a", ""},
-	{"a.b.c", "a", "b.c"},
-	{"\"a.b\".c", "a.b", "c"},
-	{"a.\"b.c\".d", "a", "\"b.c\".d"},
-	{"[1].a.d", "1", "a.d"},
-	{"a[0].c", "a", "[0].c"},
-	{"[0]", "0", ""},
-}
-
-func TestNextYamlPath(t *testing.T) {
-	for _, tt := range nextYamlPathTests {
-		var element, remaining = nextYamlPath(tt.path)
-		test.AssertResultWithContext(t, tt.expectedElement, element, tt)
-		test.AssertResultWithContext(t, tt.expectedRemaining, remaining, tt)
-	}
-}
+}
\ No newline at end of file
diff --git a/yq.go b/yq.go
index c065edc..89623ec 100644
--- a/yq.go
+++ b/yq.go
@@ -10,6 +10,7 @@ import (
 	"strconv"
 	"strings"
 	"github.com/mikefarah/yq/pkg/yqlib"
+	"github.com/mikefarah/yq/pkg/marshal"
 
 	errors "github.com/pkg/errors"
 
@@ -29,6 +30,9 @@ var verbose = false
 var version = false
 var docIndex = "0"
 var log = logging.MustGetLogger("yq")
+var lib = yqlib.NewYqLib(log)
+var jsonConverter = marshal.NewJsonConverter()
+var yamlConverter = marshal.NewYamlConverter()
 
 func main() {
 	cmd := newCommandCLI()
@@ -39,7 +43,6 @@ func main() {
 }
 
 func newCommandCLI() *cobra.Command {
-	yqlib.SetLogger(log)
 	yaml.DefaultMapType = reflect.TypeOf(yaml.MapSlice{})
 	var rootCmd = &cobra.Command{
 		Use:   "yq",
@@ -277,7 +280,7 @@ func readProperty(cmd *cobra.Command, args []string) error {
 					log.Debugf("%v", dataBucket)
 					mappedDocs = append(mappedDocs, dataBucket)
 				} else {
-					mappedDoc, errorParsing := yqlib.ReadPath(dataBucket, path)
+					mappedDoc, errorParsing := lib.ReadPath(dataBucket, path)
 					log.Debugf("%v", mappedDoc)
 					if errorParsing != nil {
 						return errors.Wrapf(errorParsing, "Error reading path in document index %v", currentIndex)
@@ -338,7 +341,7 @@ func newYaml(args []string) (interface{}, error) {
 		path := entry.Key.(string)
 		value := entry.Value
 		log.Debugf("setting %v to %v", path, value)
-		dataBucket = yqlib.WritePath(dataBucket, path, value)
+		dataBucket = lib.WritePath(dataBucket, path, value)
 	}
 
 	return dataBucket, nil
@@ -414,7 +417,7 @@ func writeProperty(cmd *cobra.Command, args []string) error {
 				path := entry.Key.(string)
 				value := entry.Value
 				log.Debugf("setting %v to %v", path, value)
-				dataBucket = yqlib.WritePath(dataBucket, path, value)
+				dataBucket = lib.WritePath(dataBucket, path, value)
 			}
 		}
 		return dataBucket, nil
@@ -437,7 +440,7 @@ func prefixProperty(cmd *cobra.Command, args []string) error {
 
 		if updateAll || currentIndex == docIndexInt {
 			log.Debugf("Prefixing %v to doc %v", prefixPath, currentIndex)
-			var mapDataBucket = yqlib.PrefixPath(dataBucket, prefixPath)
+			var mapDataBucket = lib.PrefixPath(dataBucket, prefixPath)
 			return mapDataBucket, nil
 		}
 		return dataBucket, nil
@@ -491,7 +494,7 @@ func deleteProperty(cmd *cobra.Command, args []string) error {
 	var updateData = func(dataBucket interface{}, currentIndex int) (interface{}, error) {
 		if updateAll || currentIndex == docIndexInt {
 			log.Debugf("Deleting path in doc %v", currentIndex)
-			return yqlib.DeletePath(dataBucket, deletePath)
+			return lib.DeletePath(dataBucket, deletePath)
 		}
 		return dataBucket, nil
 	}
@@ -518,7 +521,7 @@ func mergeProperties(cmd *cobra.Command, args []string) error {
 			// map
 			var mapDataBucket = make(map[interface{}]interface{})
 			mapDataBucket["root"] = dataBucket
-			if err := yqlib.Merge(&mergedData, mapDataBucket, overwriteFlag, appendFlag); err != nil {
+			if err := lib.Merge(&mergedData, mapDataBucket, overwriteFlag, appendFlag); err != nil {
 				return nil, err
 			}
 			for _, f := range filesToMerge {
@@ -530,7 +533,7 @@ func mergeProperties(cmd *cobra.Command, args []string) error {
 					return nil, err
 				}
 				mapDataBucket["root"] = fileToMerge
-				if err := yqlib.Merge(&mergedData, mapDataBucket, overwriteFlag, appendFlag); err != nil {
+				if err := lib.Merge(&mergedData, mapDataBucket, overwriteFlag, appendFlag); err != nil {
 					return nil, err
 				}
 			}
@@ -580,9 +583,9 @@ func parseValue(argument string) interface{} {
 
 func toString(context interface{}) (string, error) {
 	if outputToJSON {
-		return yqlib.JsonToString(context)
+		return jsonConverter.JsonToString(context)
 	}
-	return yqlib.YamlToString(context, trimOutput)
+	return yamlConverter.YamlToString(context, trimOutput)
 }
 
 func safelyRenameFile(from string, to string) {
diff --git a/yq_test.go b/yq_test.go
index 21d816b..2ae665f 100644
--- a/yq_test.go
+++ b/yq_test.go
@@ -5,7 +5,7 @@ import (
 	"runtime"
 	"testing"
 	"github.com/mikefarah/yq/test"
-	"github.com/mikefarah/yq/pkg/yqlib"
+	"github.com/mikefarah/yq/pkg/marshal"
 )
 
 var parseValueTests = []struct {
@@ -30,7 +30,7 @@ func TestMultilineString(t *testing.T) {
 	testString := `
 	abcd
 	efg`
-	formattedResult, _ := yqlib.YamlToString(testString, false)
+	formattedResult, _ := marshal.NewYamlConverter().YamlToString(testString, false)
 	test.AssertResult(t, testString, formattedResult)
 }
 
@@ -57,7 +57,7 @@ func TestNewYaml_WithScript(t *testing.T) {
   e:
   - name: Mike Farah`
 	result, _ := newYaml([]string{""})
-	actualResult, _ := yqlib.YamlToString(result, true)
+	actualResult, _ := marshal.NewYamlConverter().YamlToString(result, true)
 	test.AssertResult(t, expectedResult, actualResult)
 }