diff --git a/.gitignore b/.gitignore
index 0dc13de08..00e212a73 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 .DS_Store
 .release/
 .releases/
+cmd/playground/
 kopia-*.tar.gz
 kopia-*.zip
 combined.cov
diff --git a/Makefile b/Makefile
index 6a35f6a09..36ab70538 100644
--- a/Makefile
+++ b/Makefile
@@ -24,7 +24,7 @@ play:
 	go run cmd/playground/main.go
 
 lint:
-	-golint github.com/kopia/kopia/...
+	golint github.com/kopia/kopia/...
 
 vet:
 	go tool vet -all .
diff --git a/cmd/kopia/main.go b/cmd/kopia/main.go
index a8e2ba52b..a7f20f112 100644
--- a/cmd/kopia/main.go
+++ b/cmd/kopia/main.go
@@ -1,5 +1,5 @@
 /*
-The 'kopia' utility supports creating and accessing backups from command line.
+Command-line tool for creating and accessing backups.
 
 Usage:
 
diff --git a/cmd/playground/main.go b/cmd/playground/main.go
deleted file mode 100644
index 811546377..000000000
--- a/cmd/playground/main.go
+++ /dev/null
@@ -1,43 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"log"
-
-	"github.com/kopia/kopia/repo"
-	"github.com/kopia/kopia/storage/storagetesting"
-)
-
-func main() {
-	d := map[string][]byte{}
-
-	s := storagetesting.NewMapStorage(d)
-	f := repo.Format{
-		Version:      1,
-		MaxBlobSize:  100,
-		ObjectFormat: "TESTONLY_MD5",
-	}
-	r, err := repo.NewRepository(s, &f)
-	if err != nil {
-		log.Fatalf("Err: %v", err)
-	}
-	w := r.NewWriter(repo.WithDescription("tester"))
-
-	w.Write(bytes.Repeat([]byte("a"), 5000))
-	result, err := w.Result(true)
-	log.Printf("result: %v", result.UIString())
-
-	log.Printf("attempting to open")
-
-	rdr, err := r.Open(result)
-	if err != nil {
-		log.Fatalf("open: %v", err)
-	}
-	log.Printf("len: %v\n", rdr.Length())
-	log.Printf("----")
-	// for k, v := range d {
-	// 	log.Printf("%v = %v", k, string(v))
-	// }
-
-	rdr.Close()
-}
diff --git a/fuse/fusefs.go b/fuse/fusefs.go
index 553adf0f6..3ce771663 100644
--- a/fuse/fusefs.go
+++ b/fuse/fusefs.go
@@ -1,5 +1,6 @@
 // +build !windows
 
+// Package fuse implements Node FUSE filesystem APIs for mounting contents of filesystem stored in repository.
 package fuse
 
 import (
diff --git a/storage/storagetesting/asserts.go b/internal/storagetesting/asserts.go
similarity index 100%
rename from storage/storagetesting/asserts.go
rename to internal/storagetesting/asserts.go
diff --git a/storage/storagetesting/map.go b/internal/storagetesting/map.go
similarity index 100%
rename from storage/storagetesting/map.go
rename to internal/storagetesting/map.go
diff --git a/storage/storagetesting/map_test.go b/internal/storagetesting/map_test.go
similarity index 100%
rename from storage/storagetesting/map_test.go
rename to internal/storagetesting/map_test.go
diff --git a/storage/storagetesting/verify.go b/internal/storagetesting/verify.go
similarity index 100%
rename from storage/storagetesting/verify.go
rename to internal/storagetesting/verify.go
diff --git a/repo/repository_test.go b/repo/repository_test.go
index 3d2adb85c..52086d97a 100644
--- a/repo/repository_test.go
+++ b/repo/repository_test.go
@@ -13,8 +13,8 @@
 	"testing"
 
 	"github.com/kopia/kopia/internal/jsonstream"
+	"github.com/kopia/kopia/internal/storagetesting"
 	"github.com/kopia/kopia/storage"
-	"github.com/kopia/kopia/storage/storagetesting"
 )
 
 func testFormat() *Format {
diff --git a/storage/caching/caching_storage_test.go b/storage/caching/caching_storage_test.go
index 48ed89381..6a954741e 100644
--- a/storage/caching/caching_storage_test.go
+++ b/storage/caching/caching_storage_test.go
@@ -10,8 +10,8 @@
 
 	"github.com/kopia/kopia/storage"
 
+	"github.com/kopia/kopia/internal/storagetesting"
 	"github.com/kopia/kopia/storage/logging"
-	"github.com/kopia/kopia/storage/storagetesting"
 
 	"testing"
 )
diff --git a/storage/filesystem/filesystem_storage.go b/storage/filesystem/filesystem_storage.go
index 151a21974..ced219d29 100644
--- a/storage/filesystem/filesystem_storage.go
+++ b/storage/filesystem/filesystem_storage.go
@@ -1,3 +1,4 @@
+// Package filesystem implements filesystem-based Storage.
 package filesystem
 
 import (
diff --git a/storage/filesystem/filesystem_storage_test.go b/storage/filesystem/filesystem_storage_test.go
index 74dac36c7..c429a02e8 100644
--- a/storage/filesystem/filesystem_storage_test.go
+++ b/storage/filesystem/filesystem_storage_test.go
@@ -5,7 +5,7 @@
 	"os"
 	"testing"
 
-	"github.com/kopia/kopia/storage/storagetesting"
+	"github.com/kopia/kopia/internal/storagetesting"
 )
 
 func TestFileStorage(t *testing.T) {
diff --git a/storage/gcs/gcs_storage.go b/storage/gcs/gcs_storage.go
index 946352e62..904a30234 100644
--- a/storage/gcs/gcs_storage.go
+++ b/storage/gcs/gcs_storage.go
@@ -1,3 +1,4 @@
+// Package gcs implements Storage based on Google Cloud Storage bucket.
 package gcs
 
 import (
diff --git a/storage/logging/logging_storage.go b/storage/logging/logging_storage.go
index c8bc97a7d..155835e6a 100644
--- a/storage/logging/logging_storage.go
+++ b/storage/logging/logging_storage.go
@@ -1,3 +1,4 @@
+// Package logging implements wrapper around Storage that logs all activity.
 package logging
 
 import (
@@ -6,9 +7,10 @@
 	"github.com/kopia/kopia/storage"
 )
 
-// Printfer is
+// Printfer supports emitting formatted strings to arbitrary outputs.
+// The formatting language must be compatible with fmt.Sprintf().
 type Printfer interface {
-	Printf(string, ...interface{})
+	Printf(fmt string, args ...interface{})
 }
 
 type loggingStorage struct {
diff --git a/storage/logging/logging_storage_test.go b/storage/logging/logging_storage_test.go
index 2ab1d1439..fef06e52f 100644
--- a/storage/logging/logging_storage_test.go
+++ b/storage/logging/logging_storage_test.go
@@ -3,7 +3,7 @@
 import (
 	"testing"
 
-	"github.com/kopia/kopia/storage/storagetesting"
+	"github.com/kopia/kopia/internal/storagetesting"
 )
 
 func TestLoggingStorage(t *testing.T) {