diff --git a/lib/common/mapping.go b/lib/common/mapping.go
index d2f1abd..14fc973 100644
--- a/lib/common/mapping.go
+++ b/lib/common/mapping.go
@@ -14,24 +14,31 @@ type MappingValues [][2]String
 // the form of a MappingValues.
 //
 func (mapping Mapping) Values() (map_values MappingValues, errs []error) {
-	// check length and append any errors needed, max: 65537
-	// sanity check no data is missing
-
 	var str String
 	var remainder = mapping
 	var err error
+
+	length := Integer(remainder[:2])
+	remainder = remainder[2:]
+	mapping_len := len(mapping)
+	if mapping_len > length+2 {
+		errs = append(errs, errors.New("warning parsing mapping: data exists beyond length of mapping"))
+	} else if length+2 > mapping_len {
+		errs = append(errs, errors.New("warning parsing mapping: mapping length exceeds provided data"))
+	}
+
 	for {
 		// Read a key, breaking on fatal errors
 		// and appending warnings
 		str, remainder, err = ReadString(remainder)
 		key_str := str
 		if err != nil {
-			errs = append(errs, err)
 			if stopValueRead(err) {
+				errs = append(errs, err)
 				return
 			}
 		}
-		if !beginsWith(remainder, "=") {
+		if !beginsWith(remainder, 0x3d) {
 			errs = append(errs, errors.New("mapping format violation, expected ="))
 			return
 		}
@@ -42,12 +49,12 @@ func (mapping Mapping) Values() (map_values MappingValues, errs []error) {
 		str, remainder, err = ReadString(remainder)
 		val_str := str
 		if err != nil {
-			errs = append(errs, err)
 			if stopValueRead(err) {
+				errs = append(errs, err)
 				return
 			}
 		}
-		if !beginsWith(remainder, ";") {
+		if !beginsWith(remainder, 0x3b) {
 			errs = append(errs, errors.New("mapping format violation, expected ;"))
 			return
 		}
@@ -67,6 +74,16 @@ func (mapping Mapping) Values() (map_values MappingValues, errs []error) {
 // Returns true if two keys in a mapping are identical
 //
 func (mapping Mapping) HasDuplicateKeys() bool {
+	seen_values := make(map[string]bool)
+	values, _ := mapping.Values()
+	for _, pair := range values {
+		key, _ := pair[0].Data()
+		if _, present := seen_values[key]; present {
+			return true
+		} else {
+			seen_values[key] = true
+		}
+	}
 	return false
 }
 
@@ -79,8 +96,10 @@ func ValuesToMapping(values MappingValues) Mapping {
 	var mapping Mapping
 	mappingOrder(values)
 	for _, kv_pair := range values {
-		key_string := String(kv_pair[0])
-		key_value := String(kv_pair[1])
+		key_string := kv_pair[0]
+		key_string = append(key_string, []byte("=")[0])
+		key_value := kv_pair[1]
+		key_value = append(key_value, []byte(";")[0])
 		mapping = append(append(mapping, key_string...), key_value...)
 	}
 	map_len := len(mapping)
@@ -152,7 +171,7 @@ func stopValueRead(err error) bool {
 	return err.Error() == "error parsing string: zero length"
 }
 
-func beginsWith(bytes []byte, str string) bool {
+func beginsWith(bytes []byte, chr byte) bool {
 	return len(bytes) != 0 &&
-		string(bytes[0]) == str
+		bytes[0] == chr
 }
diff --git a/lib/common/mapping_test.go b/lib/common/mapping_test.go
index ecae0c9..7a46d45 100644
--- a/lib/common/mapping_test.go
+++ b/lib/common/mapping_test.go
@@ -1,5 +1,168 @@
 package common
 
 import (
-//"testing"
+	"bytes"
+	"errors"
+	"testing"
 )
+
+func TestValuesExclusesPairWithBadData(t *testing.T) {
+	bad_key := Mapping([]byte{0x00, 0x0c, 0x01, 0x61, 0x3d, 0x01, 0x62, 0x3b, 0x00})
+	values, errs := bad_key.Values()
+	if len(values) != 1 {
+		t.Fatal("Values did not return valid values when some values had bad key")
+	} else {
+		key, _ := values[0][0].Data()
+		val, _ := values[0][1].Data()
+		if key != "a" || val != "b" {
+			t.Fatal("Value returned by values when other value had invalid key was incorrect")
+		}
+	}
+	if len(errs) != 2 {
+		t.Fatal("Values reported wrong error count when some values had invalid data", errs)
+	}
+}
+
+func TestValuesWarnsMissingData(t *testing.T) {
+	mapping := Mapping([]byte{0x00, 0x06, 0x01, 0x61, 0x3d, 0x01, 0x62})
+	_, errs := mapping.Values()
+	if len(errs) != 2 || errs[0].Error() != "warning parsing mapping: mapping length exceeds provided data" {
+		t.Fatal("Values reported wrong error when missing data", len(errs), errs)
+	}
+}
+
+func TestValuesWarnsExtraData(t *testing.T) {
+	mapping := Mapping([]byte{0x00, 0x06, 0x01, 0x61, 0x3d, 0x01, 0x62, 0x3b, 0x00})
+	_, errs := mapping.Values()
+	if len(errs) != 2 || errs[0].Error() != "warning parsing mapping: data exists beyond length of mapping" {
+		t.Fatal("Values reported wrong error when extra data", len(errs), errs)
+	}
+}
+
+func TestValuesEnforcesEqualDelimitor(t *testing.T) {
+	mapping := Mapping([]byte{0x00, 0x06, 0x01, 0x61, 0x30, 0x01, 0x62, 0x3b})
+	values, errs := mapping.Values()
+	if len(errs) != 1 || errs[0].Error() != "mapping format violation, expected =" {
+		t.Fatal("wrong error reported with equal format error", errs)
+	}
+	if len(values) != 0 {
+		t.Fatal("values not empty with invalid data, equal error")
+	}
+}
+
+func TestValuesEnforcedSemicolonDelimitor(t *testing.T) {
+	mapping := Mapping([]byte{0x00, 0x06, 0x01, 0x61, 0x3d, 0x01, 0x62, 0x30})
+	values, errs := mapping.Values()
+	if len(errs) != 1 || errs[0].Error() != "mapping format violation, expected ;" {
+		t.Fatal("wrong error reported with semicolon format error", errs)
+	}
+	if len(values) != 0 {
+		t.Fatal("values not empty with invalid data, semicolon error")
+	}
+}
+
+func TestValuesReturnsValues(t *testing.T) {
+	mapping := Mapping([]byte{0x00, 0x06, 0x01, 0x61, 0x3d, 0x01, 0x62, 0x3b})
+	_, errs := mapping.Values()
+	if errs != nil {
+		t.Fatal("errs when parsing valid mapping values", errs)
+	}
+}
+
+func TestHasDuplicateKeysTrueWhenDuplicates(t *testing.T) {
+	dups := Mapping([]byte{0x00, 0x0c, 0x01, 0x61, 0x3d, 0x01, 0x62, 0x3b, 0x01, 0x61, 0x3d, 0x01, 0x62, 0x3b})
+	if dups.HasDuplicateKeys() != true {
+		t.Fatal("HasDuplicateKeys did not report true when duplicate keys present")
+	}
+}
+
+func TestHasDuplicateKeysFalseWithoutDuplicates(t *testing.T) {
+	mapping := Mapping([]byte{0x00, 0x06, 0x01, 0x61, 0x3d, 0x01, 0x62, 0x3b})
+	if mapping.HasDuplicateKeys() != false {
+		t.Fatal("HasDuplicateKeys did not report false when duplicate keys were not present")
+	}
+}
+
+func TestGoMapToMappingProducesCorrectMapping(t *testing.T) {
+	gomap := map[string]string{"a": "b"}
+	mapping, err := GoMapToMapping(gomap)
+	if err != nil {
+		t.Fatal("GoMapToMapping returned error with valid data", err)
+	}
+	expected := []byte{0x00, 0x06, 0x01, 0x61, 0x3d, 0x01, 0x62, 0x3b}
+	if bytes.Compare(mapping, expected) != 0 {
+		t.Fatal("GoMapToMapping did not produce correct Mapping", mapping, expected)
+	}
+}
+
+func TestMappingOrderSortsValuesThenKeys(t *testing.T) {
+	a, _ := ToI2PString("a")
+	b, _ := ToI2PString("b")
+	values := MappingValues{
+		[2]String{b, b},
+		[2]String{b, a},
+		[2]String{a, b},
+		[2]String{a, a},
+	}
+	mappingOrder(values)
+	for i, pair := range values {
+		key, _ := pair[0].Data()
+		value, _ := pair[1].Data()
+		switch i {
+		case 0:
+			if !(key == "a" && value == "a") {
+				t.Fatal("mappingOrder produced incorrect sort output at", i)
+			}
+		case 1:
+			if !(key == "a" && value == "b") {
+				t.Fatal("mappingOrder produced incorrect sort output at", i)
+			}
+		case 2:
+			if !(key == "b" && value == "a") {
+				t.Fatal("mappingOrder produced incorrect sort output at", i)
+			}
+		case 3:
+			if !(key == "b" && value == "b") {
+				t.Fatal("mappingOrder produced incorrect sort output at", i)
+			}
+		}
+	}
+}
+
+func TestStopValueReadTrueWhenCorrectErr(t *testing.T) {
+	status := stopValueRead(errors.New("error parsing string: zero length"))
+	if status != true {
+		t.Fatal("stopValueRead not true when String error found")
+	}
+}
+
+func TestStopValueReadFalseWhenWrongErr(t *testing.T) {
+	status := stopValueRead(errors.New("something else"))
+	if status != false {
+		t.Fatal("stopValueRead not false when error not String error")
+	}
+}
+
+func TestBeginsWithCorrectWhenTrue(t *testing.T) {
+	slice := []byte{0x41}
+	status := beginsWith(slice, 0x41)
+	if status != true {
+		t.Fatal("beginsWith did not return false on empty slice")
+	}
+}
+
+func TestBeginsWithCorrectWhenFalse(t *testing.T) {
+	slice := []byte{0x00}
+	status := beginsWith(slice, 0x41)
+	if status != false {
+		t.Fatal("beginsWith did not return false on empty slice")
+	}
+}
+
+func TestBeginsWithCorrectWhenNil(t *testing.T) {
+	slice := make([]byte, 0)
+	status := beginsWith(slice, 0x41)
+	if status != false {
+		t.Fatal("beginsWith did not return false on empty slice")
+	}
+}
diff --git a/lib/common/string_test.go b/lib/common/string_test.go
index acf0065..3a77e49 100644
--- a/lib/common/string_test.go
+++ b/lib/common/string_test.go
@@ -106,43 +106,43 @@ func TestReadStringReadsLength(t *testing.T) {
 	bytes := []byte{0x01, 0x04, 0x06}
 	str, remainder, err := ReadString(bytes)
 	if err == nil || err.Error() != "string parsing warning: string contains data beyond length" {
-		t.Fatal("ReadString(t *testing.T) returned incorrect error,", err)
+		t.Fatal("ReadString() returned incorrect error,", err)
 	}
 	if len(str) != 2 {
-		t.Fatal("ReadString(t *testing.T) did not return correct string length:", len(str))
+		t.Fatal("ReadString() did not return correct string length:", len(str))
 	}
 	if str[0] != 0x01 && str[1] != 0x04 {
-		t.Fatal("ReadString(t *testing.T) did not return correct string")
+		t.Fatal("ReadString() did not return correct string")
 	}
 	if len(remainder) != 1 {
-		t.Fatal("ReadString(t *testing.T) did not return correct remainder length")
+		t.Fatal("ReadString() did not return correct remainder length")
 	}
 	if remainder[0] != 0x06 {
-		t.Fatal("ReadString(t *testing.T) did not return correct remainder")
+		t.Fatal("ReadString() did not return correct remainder")
 	}
 }
 
 func TestReadStringErrWhenEmptySlice(t *testing.T) {
 	bytes := make([]byte, 0)
 	_, _, err := ReadString(bytes)
-	if err != nil && err.Error() != "error parsing string: zero length" {
-		t.Fatal("ReadString(t *testing.T) did not report empty slice error", err)
+	if err == nil || err.Error() != "error parsing string: zero length" {
+		t.Fatal("ReadString() did not report empty slice error", err)
 	}
 }
 
 func TestReadStringErrWhenDataTooShort(t *testing.T) {
-	bytes := []byte{0x03, 0x01}
-	str, remainder, err := ReadString(bytes)
-	if err != nil && err.Error() != "string parsing warning: string data is shorter than specified by length" {
-		t.Fatal("ReadString(t *testing.T) did not report string too long", err)
+	short_str := []byte{0x03, 0x01}
+	str, remainder, err := ReadString(short_str)
+	if err == nil || err.Error() != "string parsing warning: string data is shorter than specified by length" {
+		t.Fatal("ReadString() did not report string too long:", err)
 	}
 	if len(str) != 2 {
-		t.Fatal("ReadString(t *testing.T) did not return the slice as string when too long")
+		t.Fatal("ReadString() did not return the slice as string when too long")
 	}
 	if str[0] != 0x03 && str[1] != 0x01 {
-		t.Fatal("ReadString(t *testing.T) did not return the correct partial string")
+		t.Fatal("ReadString() did not return the correct partial string")
 	}
 	if len(remainder) != 0 {
-		t.Fatal("ReadString(t *testing.T) returned a remainder when the string data was too short")
+		t.Fatal("ReadString() returned a remainder when the string data was too short")
 	}
 }