app: Test that PID file is removed

app.go

@@ -142,11 +142,13 @@ func (a *App) runShutdownHooks(ctx context.Context) error {
 	return nil
 }
 
+var background = context.Background()
+
 // Run will start the App, running the startup Hooks, then the Processes.
 // It will wait for any signals before shutting down first the Processes then the shutdown Hooks.
 // This behaviour can be customised by using Launch, WaitForShutdown, and Shutdown.
 func (a *App) Run() int {
-	ac := NewAppContext(context.Background())
+	ac := NewAppContext(background)
 	defer ac.Stop()
 	defer a.cleanup(ac.TerminationContext)
 

app_internal_test.go

@@ -0,0 +1,12 @@
+package lu
+
+import (
+	"context"
+	"testing"
+)
+
+func SetBackgroundContextForTesting(t *testing.T, ctx context.Context) {
+	old := background
+	t.Cleanup(func() { background = old })
+	background = ctx
+}

app_test.go

@@ -2,11 +2,14 @@ package lu_test
 
 import (
 	"context"
+	"io"
+	"os"
 	"testing"
 	"time"
 
 	"github.com/luno/jettison/jtest"
 	"github.com/luno/jettison/log"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
 	"github.com/luno/lu"
@@ -237,3 +240,66 @@ func TestRunningProcesses(t *testing.T) {
 		})
 	}
 }
+
+func TestPIDRemoved(t *testing.T) {
+	tests := []struct {
+		name    string
+		app     func(t *testing.T) *lu.App
+		expExit int
+	}{
+		{
+			name: "not using pid",
+			app: func(t *testing.T) *lu.App {
+				var a lu.App
+				a.AddProcess(process.NoOp())
+				return &a
+			},
+			expExit: 1,
+		},
+		{
+			name: "normal app",
+			app: func(t *testing.T) *lu.App {
+				a := lu.App{UseProcessFile: true}
+				a.AddProcess(process.NoOp())
+				return &a
+			},
+			expExit: 1,
+		},
+		{
+			name: "app fails to start",
+			app: func(t *testing.T) *lu.App {
+				a := lu.App{UseProcessFile: true}
+				a.OnStartUp(func(ctx context.Context) error {
+					return io.ErrUnexpectedEOF
+				})
+				a.AddProcess(process.NoOp())
+				return &a
+			},
+			expExit: 1,
+		},
+		{
+			name: "app fails to shutdown",
+			app: func(t *testing.T) *lu.App {
+				a := lu.App{UseProcessFile: true}
+				a.OnShutdown(func(ctx context.Context) error {
+					return io.ErrUnexpectedEOF
+				})
+				a.AddProcess(process.NoOp())
+				return &a
+			},
+			expExit: 1,
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+			t.Cleanup(cancel)
+			lu.SetBackgroundContextForTesting(t, ctx)
+
+			exit := tc.app(t).Run()
+			assert.Equal(t, tc.expExit, exit)
+			_, err := os.Open("/tmp/lu.pid")
+			assert.True(t, os.IsNotExist(err))
+		})
+	}
+}