diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
new file mode 100644
index 0000000..7ed36bd
--- /dev/null
+++ b/.github/workflows/pr.yml
@@ -0,0 +1,59 @@
+
+name: PR Check
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+jobs:
+  vet:
+    defaults:
+      run:
+        working-directory: mpd-web-proxy
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up Go
+      uses: actions/setup-go@v4
+      with:
+        go-version: '1.22'
+
+    - run: go mod download
+
+    - name: Go Vet
+      run: go vet ./...
+
+  unit-test:
+    defaults:
+      run:
+        working-directory: mpd-web-proxy
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        lfs: true
+
+    - name: Set up Go
+      uses: actions/setup-go@v4
+      with:
+        go-version: '1.22'
+
+    - run: go mod download
+
+    - run: go install github.com/jstemmer/go-junit-report/v2@latest
+
+    - name: Unit Test
+      run: |
+        set +e
+        go test -v ./... | tee test.out
+        exitcode=$?
+        cat test.out | ~/go/bin/go-junit-report -set-exit-code > junit.xml
+        exit $exitcode
+
+    - if: always()
+      uses: EnricoMi/publish-unit-test-result-action@v2
+      with:
+        files: mpd-web-proxy/junit.xml
+
diff --git a/mpd-web-proxy/Dockerfile b/mpd-web-proxy/Dockerfile
index 2a7461e..2acfb3b 100644
--- a/mpd-web-proxy/Dockerfile
+++ b/mpd-web-proxy/Dockerfile
@@ -9,10 +9,9 @@ ARG VERSION='development'
 COPY go.mod go.sum ./
 RUN go mod download
 COPY *.go ./
-COPY gpio/ ./gpio/
-COPY art/ ./art/
-COPY version/ ./version/
+COPY cmd/ ./cmd/
+COPY internal/ ./internal/
 
-RUN go build -ldflags "-X 'github.com/aspage2/remote/mpd-web-proxy/version.Version=${VERSION}'" -o /app/main
+RUN go build -ldflags "-X 'github.com/aspage2/remote/mpd-web-proxy/internal/version.Version=${VERSION}'" -o /app/main /app/cmd
 
 ENTRYPOINT ["/app/main"]
diff --git a/mpd-web-proxy/Makefile b/mpd-web-proxy/Makefile
index b6da947..dc11b46 100644
--- a/mpd-web-proxy/Makefile
+++ b/mpd-web-proxy/Makefile
@@ -2,4 +2,4 @@
 VERSION = $(shell git describe --exact-match --match='v[0-9].*' HEAD 2>/dev/null || git rev-parse --short  HEAD)
 
 build/mpd-web-proxy: $(wildcard **/*.go *.go)
-	go build -ldflags="-X 'github.com/aspage2/remote/mpd-web-proxy.Version=$(VERSION)'" -o build/mpd-web-proxy .
+	go build -ldflags="-X 'github.com/aspage2/remote/mpd-web-proxy/internal.Version=$(VERSION)'" -o build/mpd-web-proxy ./cmd
diff --git a/mpd-web-proxy/config.go b/mpd-web-proxy/cmd/config.go
similarity index 100%
rename from mpd-web-proxy/config.go
rename to mpd-web-proxy/cmd/config.go
diff --git a/mpd-web-proxy/main.go b/mpd-web-proxy/cmd/main.go
similarity index 92%
rename from mpd-web-proxy/main.go
rename to mpd-web-proxy/cmd/main.go
index db96940..eff949f 100644
--- a/mpd-web-proxy/main.go
+++ b/mpd-web-proxy/cmd/main.go
@@ -14,9 +14,10 @@ import (
 	"runtime/debug"
 	"strings"
 
-	"github.com/aspage2/remote/mpd-web-proxy/art"
-	"github.com/aspage2/remote/mpd-web-proxy/gpio"
-	"github.com/aspage2/remote/mpd-web-proxy/version"
+	"github.com/aspage2/remote/mpd-web-proxy/internal"
+	"github.com/aspage2/remote/mpd-web-proxy/internal/art"
+	"github.com/aspage2/remote/mpd-web-proxy/internal/gpio"
+	"github.com/aspage2/remote/mpd-web-proxy/internal/version"
 )
 
 const (
@@ -28,7 +29,7 @@ const (
 type Server struct {
 	Pins          []gpio.Pin
 	PinState      *gpio.PinState
-	MPDStateTopic *Topic[Event]
+	MPDStateTopic *internal.Topic[internal.Event]
 }
 
 func (s *Server) WriteResponse(wr io.Writer) error {
@@ -119,7 +120,7 @@ func (s *Server) MpdEvents(rw http.ResponseWriter, req *http.Request) {
 		io.Copy(io.Discard, req.Body)
 	}()
 
-	for ev := range getEvents(s.MPDStateTopic, req.Context()) {
+	for ev := range internal.GetEvents(s.MPDStateTopic, req.Context()) {
 		eventPayload := ev.SSEPayload()
 		_, err := io.WriteString(rw, eventPayload)
 		if err != nil {
@@ -141,7 +142,7 @@ func MpdCommand(rw http.ResponseWriter, req *http.Request) {
 		return
 	}
 	q := qs[0]
-	data := Must(MpdQuery(q))
+	data := Must(internal.MpdQuery(q, MpdAuthority))
 	rw.Write(data)
 }
 
@@ -237,7 +238,7 @@ func httpServer(s *Server) {
 	nonEventMux.HandleFunc("/go/channels", s.Channels)
 	nonEventMux.HandleFunc("/go/art/{albumartist}/{album}", AlbumArt)
 
-	http.Handle("/go/", loggingMiddleware(&PanicCatchall{&nonEventMux}))
+	http.Handle("/go/", internal.LoggingMiddleware(&PanicCatchall{&nonEventMux}))
 	http.Handle("/go/events", &PanicCatchall{http.HandlerFunc(s.MpdEvents)})
 
 	http.ListenAndServe(BindAddr, nil)
@@ -290,7 +291,7 @@ func main() {
 	var s Server
 	s.PinState = ps
 	s.Pins = pins
-	s.MPDStateTopic = NewTopic[Event]()
-	go MPDIdler(s.MPDStateTopic)
+	s.MPDStateTopic = internal.NewTopic[internal.Event]()
+	go internal.MPDIdler(s.MPDStateTopic, MpdAuthority)
 	httpServer(&s)
 }
diff --git a/mpd-web-proxy/art/art.go b/mpd-web-proxy/internal/art/art.go
similarity index 100%
rename from mpd-web-proxy/art/art.go
rename to mpd-web-proxy/internal/art/art.go
diff --git a/mpd-web-proxy/art/art_test.go b/mpd-web-proxy/internal/art/art_test.go
similarity index 87%
rename from mpd-web-proxy/art/art_test.go
rename to mpd-web-proxy/internal/art/art_test.go
index 67492b1..46d8130 100644
--- a/mpd-web-proxy/art/art_test.go
+++ b/mpd-web-proxy/internal/art/art_test.go
@@ -8,8 +8,10 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+const DataPath = "../../testdata/file.mp3"
+
 func TestFindAPIC(t *testing.T) {
-	f, err := os.Open("../testdata/file.mp3")
+	f, err := os.Open(DataPath)
 	assert.NoError(t, err)
 
 	mime, size, err := FindAPICInMP3(f)
@@ -22,7 +24,7 @@ func TestFindAPIC(t *testing.T) {
 }
 
 func BenchmarkFindAPICInMP3(b *testing.B) {
-	f, err := os.Open("../testdata/file.mp3")
+	f, err := os.Open(DataPath)
 	if err != nil {
 		panic(err)
 	}
diff --git a/mpd-web-proxy/art/id3.go b/mpd-web-proxy/internal/art/id3.go
similarity index 100%
rename from mpd-web-proxy/art/id3.go
rename to mpd-web-proxy/internal/art/id3.go
diff --git a/mpd-web-proxy/art/id3_test.go b/mpd-web-proxy/internal/art/id3_test.go
similarity index 100%
rename from mpd-web-proxy/art/id3_test.go
rename to mpd-web-proxy/internal/art/id3_test.go
diff --git a/mpd-web-proxy/events.go b/mpd-web-proxy/internal/events.go
similarity index 92%
rename from mpd-web-proxy/events.go
rename to mpd-web-proxy/internal/events.go
index b0445eb..9ead276 100644
--- a/mpd-web-proxy/events.go
+++ b/mpd-web-proxy/internal/events.go
@@ -1,4 +1,4 @@
-package main
+package internal
 
 import (
 	"bufio"
@@ -62,11 +62,11 @@ func (ev Event) SSEPayload() string {
 // event and tries to re-create the connection. After re-
 // connecting, the idler sends a `server:mpd-connected`
 // event and continues idling.
-func MPDIdler(tpc *Topic[Event]) {
+func MPDIdler(tpc *Topic[Event], authority string) {
 	oneRound := func() error {
 		slog.Info("start idler")
 		defer slog.Info("stop idler")
-		mpd, err := net.Dial("tcp", MpdAuthority)
+		mpd, err := net.Dial("tcp", authority)
 		if err != nil {
 			return err
 		}
@@ -124,9 +124,9 @@ func mpdIdle(mpd net.Conn, tpc *Topic[Event]) error {
 	}
 }
 
-// getEvents wraps the given Topic[Event] with a ticker
+// GetEvents wraps the given Topic[Event] with a ticker
 // that sends a `ping` event every 5 seconds.
-func getEvents(tpc *Topic[Event], ctx context.Context) chan Event {
+func GetEvents(tpc *Topic[Event], ctx context.Context) chan Event {
 	ret := make(chan Event)
 	go func() {
 		defer close(ret)
diff --git a/mpd-web-proxy/gpio/amd.go b/mpd-web-proxy/internal/gpio/amd.go
similarity index 100%
rename from mpd-web-proxy/gpio/amd.go
rename to mpd-web-proxy/internal/gpio/amd.go
diff --git a/mpd-web-proxy/gpio/arm.go b/mpd-web-proxy/internal/gpio/arm.go
similarity index 100%
rename from mpd-web-proxy/gpio/arm.go
rename to mpd-web-proxy/internal/gpio/arm.go
diff --git a/mpd-web-proxy/gpio/config.go b/mpd-web-proxy/internal/gpio/config.go
similarity index 100%
rename from mpd-web-proxy/gpio/config.go
rename to mpd-web-proxy/internal/gpio/config.go
diff --git a/mpd-web-proxy/gpio/gpio.go b/mpd-web-proxy/internal/gpio/gpio.go
similarity index 100%
rename from mpd-web-proxy/gpio/gpio.go
rename to mpd-web-proxy/internal/gpio/gpio.go
diff --git a/mpd-web-proxy/gpio/state.go b/mpd-web-proxy/internal/gpio/state.go
similarity index 100%
rename from mpd-web-proxy/gpio/state.go
rename to mpd-web-proxy/internal/gpio/state.go
diff --git a/mpd-web-proxy/logging.go b/mpd-web-proxy/internal/logging.go
similarity index 92%
rename from mpd-web-proxy/logging.go
rename to mpd-web-proxy/internal/logging.go
index d1583e5..c5ff3c3 100644
--- a/mpd-web-proxy/logging.go
+++ b/mpd-web-proxy/internal/logging.go
@@ -1,4 +1,4 @@
-package main
+package internal
 
 import (
 	"fmt"
@@ -26,7 +26,7 @@ func (lr *StatusCaptureRW) WriteHeader(code int) {
 	lr.ResponseWriter.WriteHeader(code)
 }
 
-func loggingMiddleware(next http.Handler) http.Handler {
+func LoggingMiddleware(next http.Handler) http.Handler {
 	f := func(rw http.ResponseWriter, req *http.Request) {
 		sc := NewStatusCaptureRW(rw)
 		next.ServeHTTP(sc, req)
diff --git a/mpd-web-proxy/mpd.go b/mpd-web-proxy/internal/mpd.go
similarity index 83%
rename from mpd-web-proxy/mpd.go
rename to mpd-web-proxy/internal/mpd.go
index 51d90aa..3de42bc 100644
--- a/mpd-web-proxy/mpd.go
+++ b/mpd-web-proxy/internal/mpd.go
@@ -1,4 +1,4 @@
-package main
+package internal
 
 import (
 	"bufio"
@@ -14,8 +14,8 @@ import (
 // MpdQuery connects and queries the MPD server
 // with the given command. Returns the response body
 // or any connection error.
-func MpdQuery(cmd string) ([]byte, error) {
-	mpd, err := net.Dial("tcp", MpdAuthority)
+func MpdQuery(cmd string, authority string) ([]byte, error) {
+	mpd, err := net.Dial("tcp", authority)
 	if err != nil {
 		return nil, err
 	}
@@ -24,8 +24,8 @@ func MpdQuery(cmd string) ([]byte, error) {
 }
 
 // A cancellable MPD Query.
-func MpdQueryContext(cmd string, ctx context.Context) ([]byte, error) {
-	mpd, err := net.Dial("tcp", MpdAuthority)
+func MpdQueryContext(cmd string, authority string, ctx context.Context) ([]byte, error) {
+	mpd, err := net.Dial("tcp", authority)
 	if err != nil {
 		return nil, err
 	}
diff --git a/mpd-web-proxy/topic.go b/mpd-web-proxy/internal/topic.go
similarity index 97%
rename from mpd-web-proxy/topic.go
rename to mpd-web-proxy/internal/topic.go
index 205fb2b..7b255c4 100644
--- a/mpd-web-proxy/topic.go
+++ b/mpd-web-proxy/internal/topic.go
@@ -1,4 +1,4 @@
-package main
+package internal
 
 import (
 	"log/slog"
diff --git a/mpd-web-proxy/version/version.go b/mpd-web-proxy/internal/version/version.go
similarity index 100%
rename from mpd-web-proxy/version/version.go
rename to mpd-web-proxy/internal/version/version.go