launchd: implement 'Start()' function

Implement and test the 'Start()' function for the 'launchd' daemon process
manager. The 'Start()' function assumes that the specified service has
already been boostrapped (with 'Create()'), and simply runs 'launchctl
kickstart' to start the service. If the service is already running,
'Start()' is effectively a no-op (as 'launchctl kickstart' does not restart
the already-running process).

Signed-off-by: Victoria Dye <[email protected]>

Author: vdye

internal/daemon/launchd.go

@@ -164,7 +164,23 @@ func (l *launchd) Create(config *DaemonConfig, force bool) error {
 }
 
 func (l *launchd) Start(label string) error {
-	return fmt.Errorf("not implemented")
+	user, err := l.user.CurrentUser()
+	if err != nil {
+		return fmt.Errorf("could not get current user for launchd service: %w", err)
+	}
+
+	domainTarget := fmt.Sprintf(domainFormat, user.Uid)
+	serviceTarget := fmt.Sprintf("%s/%s", domainTarget, label)
+	exitCode, err := l.cmdExec.Run("launchctl", "kickstart", serviceTarget)
+	if err != nil {
+		return err
+	}
+
+	if exitCode != 0 {
+		return fmt.Errorf("'launchctl kickstart' exited with status %d", exitCode)
+	}
+
+	return nil
 }
 
 func (l *launchd) Stop(label string) error {

internal/daemon/launchd_test.go

@@ -216,3 +216,45 @@ func TestLaunchd_Create(t *testing.T) {
 		assert.Contains(t, fileContents, fmt.Sprintf("<key>Program</key><string>%s</string>", basicDaemonConfig.Program))
 	})
 }
+
+func TestLaunchd_Start(t *testing.T) {
+	// Set up mocks
+	testUser := &user.User{
+		Uid:      "123",
+		Username: "testuser",
+	}
+	testUserProvider := &mockUserProvider{}
+	testUserProvider.On("CurrentUser").Return(testUser, nil)
+
+	testCommandExecutor := &mockCommandExecutor{}
+
+	launchd := daemon.NewLaunchdProvider(testUserProvider, testCommandExecutor, nil)
+
+	// Test #1: launchctl succeeds
+	t.Run("Calls correct launchctl command", func(t *testing.T) {
+		testCommandExecutor.On("Run",
+			"launchctl",
+			[]string{"kickstart", fmt.Sprintf("gui/123/%s", basicDaemonConfig.Label)},
+		).Return(0, nil).Once()
+
+		err := launchd.Start(basicDaemonConfig.Label)
+		assert.Nil(t, err)
+		mock.AssertExpectationsForObjects(t, testCommandExecutor)
+	})
+
+	// Reset the mock structure between tests
+	testCommandExecutor.Mock = mock.Mock{}
+
+	// Test #2: launchctl fails
+	t.Run("Returns error when launchctl fails", func(t *testing.T) {
+		testCommandExecutor.On("Run",
+			mock.AnythingOfType("string"),
+			mock.AnythingOfType("[]string"),
+		).Return(1, nil).Once()
+
+		err := launchd.Start(basicDaemonConfig.Label)
+		assert.NotNil(t, err)
+		mock.AssertExpectationsForObjects(t, testCommandExecutor)
+	})
+}
+