diff --git a/Makefile b/Makefile
index 56f4d1c..ca05329 100644
--- a/Makefile
+++ b/Makefile
@@ -3,9 +3,8 @@ all: build
 build:
 	@go build
 
-test: all
-	go test -tags=online ./...
-	./e2e.sh
+test:
+	go test -tags=online,e2e ./...
 
 install:
 	@go install
diff --git a/e2e.sh b/e2e.sh
deleted file mode 100755
index 54bdb2d..0000000
--- a/e2e.sh
+++ /dev/null
@@ -1,14 +0,0 @@
-#!/bin/sh
-
-set -e
-
-for given in testdata/*_modules.txt; do
-    m=${given#testdata/}
-    m=${m%_modules.txt}
-    expected=testdata/${m}_expected.txt
-    actual=/tmp/${m}_actual.txt
-
-    ./modules2tuple ${given} > ${actual}
-    diff -u ${expected} ${actual}
-    rm ${actual}
-done
diff --git a/go.mod b/go.mod
index 9e35f71..ef8e489 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,5 @@
 module github.com/dmgk/modules2tuple
 
 go 1.13
+
+require github.com/sergi/go-diff v1.1.0
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..4dedeae
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,21 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
+github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/sergi/go-diff v1.1.0 h1:we8PVUC3FE2uYfodKH/nBHMSetSfHDR6scGdBi+erh0=
+github.com/sergi/go-diff v1.1.0/go.mod h1:STckp+ISIX8hZLjrqAeVduY0gWCT9IjLuqbuNXdaHfM=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
+github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.2.4 h1:/eiJrUcujPVeJ3xlSWaiNi3uSVmDGBK1pDHUHAnao1I=
+gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
diff --git a/parser/parser_e2e_test.go b/parser/parser_e2e_test.go
new file mode 100644
index 0000000..a7808b5
--- /dev/null
+++ b/parser/parser_e2e_test.go
@@ -0,0 +1,78 @@
+// +build e2e
+
+package parser
+
+import (
+	"fmt"
+	"io/ioutil"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/sergi/go-diff/diffmatchpatch"
+)
+
+const testdataPath = "../testdata"
+
+type example struct {
+	modules, expected string
+}
+
+func TestParserE2E(t *testing.T) {
+	examples, err := loadExamples()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for n, x := range examples {
+		expected, err := ioutil.ReadFile(x.expected)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		actual, err := Load(x.modules)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		dmp := diffmatchpatch.New()
+		diffs := dmp.DiffMain(strings.TrimSpace(string(expected)), strings.TrimSpace(actual.String()), false)
+		if dmp.DiffLevenshtein(diffs) > 0 {
+			t.Errorf("%s: expected output doesn't match actual:\n%s", n, dmp.DiffPrettyText(diffs))
+		}
+	}
+}
+
+func loadExamples() (map[string]*example, error) {
+	res := map[string]*example{}
+
+	dir, err := ioutil.ReadDir(testdataPath)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, f := range dir {
+		name := f.Name()
+		parts := strings.SplitN(strings.TrimSuffix(name, filepath.Ext(name)), "_", 2)
+		if len(parts) < 2 {
+			return nil, fmt.Errorf("unexpected testdata file name: %q", name)
+		}
+		key, kind := parts[0], parts[1]
+
+		x, ok := res[key]
+		if !ok {
+			x = &example{}
+			res[key] = x
+		}
+		switch kind {
+		case "modules":
+			x.modules = filepath.Join(testdataPath, name)
+		case "expected":
+			x.expected = filepath.Join(testdataPath, name)
+		default:
+			return nil, fmt.Errorf("unexpected testdata file name: %q", name)
+		}
+	}
+
+	return res, nil
+}
diff --git a/parser/parser_offline_test.go b/parser/parser_offline_test.go
index faec68e..895a3ec 100644
--- a/parser/parser_offline_test.go
+++ b/parser/parser_offline_test.go
@@ -1,4 +1,4 @@
-// +build !online
+// +build !online,!e2e
 
 package parser
 
diff --git a/tuple/tuple.go b/tuple/tuple.go
index 1f33112..2843fa3 100644
--- a/tuple/tuple.go
+++ b/tuple/tuple.go
@@ -106,7 +106,7 @@ type Tuple struct {
 	source   Source // tuple source (Github ot Gitlab)
 	account  string // source account
 	project  string // source project
-	hidden   bool
+	hidden   bool   // if true, tuple will be excluded from G{H,L}_TUPLE
 }
 
 var underscoreRe = regexp.MustCompile(`[^\w]+`)
@@ -363,14 +363,6 @@ func fixGithubProjectsAndTags(s Slice) error {
 	return nil
 }
 
-// func reverseVersion(v string) string {
-//     parts := strings.Split(v, "/")
-//     for i, j := 0, len(parts)-1; i < j; i, j = i+1, j-1 {
-//         parts[i], parts[j] = parts[j], parts[i]
-//     }
-//     return strings.Join(parts, "/")
-// }
-
 // fixSubdirs ensures that all subdirs are unique and makes symlinks as needed.
 func fixSubdirs(s Slice) {
 	var maxSubdir, maxVersion, maxModule int
@@ -427,6 +419,8 @@ func fixSubdirs(s Slice) {
 	}
 }
 
+// fixFsNotify takes care of fsnotify annoying ability to appear under multiple different import paths.
+// github.com/fsnotify/fsnotify is the canonical package name.
 func fixFsNotify(s Slice) {
 	key := func(i int) string {
 		return fmt.Sprintf("%s:%s:%s:%s", s[i].account, s[i].project, s[i].version, s[i].group)
@@ -460,6 +454,7 @@ func fixFsNotify(s Slice) {
 // Otherwise omit the first line continuation for more compact representation.
 const largeLimit = 3
 
+// String returns G{H,L}_TUPLE variables contents.
 func (s Slice) String() string {
 	sort.Slice(s, func(i, j int) bool {
 		return s[i].defaultSortKey() < s[j].defaultSortKey()
@@ -507,6 +502,7 @@ func (s Slice) String() string {
 
 type Links []*Tuple
 
+// Links returns a slice of tuples that require symlinking.
 func (s Slice) Links() Links {
 	var res Links
 
@@ -525,7 +521,7 @@ func (s Slice) Links() Links {
 	return res
 }
 
-// String generates "post-extract" target that creates required symlinks.
+// String returns "post-extract" target contents.
 func (l Links) String() string {
 	if len(l) == 0 {
 		return ""