PLT-5755: Infrastructure for Component Testing. (#5814)

This migrates the existing webapp tests to using Jest and Enzyme. The
infrastructure is put in place for React component testing, and a few
simple example component tests are implemented.

This also adds snapshot testing of components, coverage checking for the
webapp (although that is not yet integrated to Coveralls), and the
ability to run npm run test:watch to automatically re-run affected tests
when working on the webapp codebase.

cmd/platform/test.go

@@ -10,9 +10,12 @@ import (
 	"os/exec"
 
 	"github.com/mattermost/platform/api"
+	"github.com/mattermost/platform/api4"
 	"github.com/mattermost/platform/app"
 	"github.com/mattermost/platform/utils"
 	"github.com/spf13/cobra"
+	"os/signal"
+	"syscall"
 )
 
 var testCmd = &cobra.Command{
@@ -27,9 +30,16 @@ var runWebClientTestsCmd = &cobra.Command{
 	RunE:  webClientTestsCmdF,
 }
 
+var runServerForWebClientTestsCmd = &cobra.Command{
+	Use:   "web_client_tests_server",
+	Short: "Run the server configured for running the web client tests against it",
+	RunE:  serverForWebClientTestsCmdF,
+}
+
 func init() {
 	testCmd.AddCommand(
 		runWebClientTestsCmd,
+		runServerForWebClientTestsCmd,
 	)
 }
 
@@ -37,6 +47,7 @@ func webClientTestsCmdF(cmd *cobra.Command, args []string) error {
 	initDBCommandContextCobra(cmd)
 	utils.InitTranslations(utils.Cfg.LocalizationSettings)
 	api.InitRouter()
+	api4.InitApi(false)
 	api.InitApi()
 	setupClientTests()
 	app.StartServer()
@@ -46,6 +57,24 @@ func webClientTestsCmdF(cmd *cobra.Command, args []string) error {
 	return nil
 }
 
+func serverForWebClientTestsCmdF(cmd *cobra.Command, args []string) error {
+	initDBCommandContextCobra(cmd)
+	utils.InitTranslations(utils.Cfg.LocalizationSettings)
+	api.InitRouter()
+	api4.InitApi(false)
+	api.InitApi()
+	setupClientTests()
+	app.StartServer()
+
+	c := make(chan os.Signal)
+	signal.Notify(c, os.Interrupt, syscall.SIGINT, syscall.SIGTERM)
+	<-c
+
+	app.StopServer()
+
+	return nil
+}
+
 func setupClientTests() {
 	*utils.Cfg.TeamSettings.EnableOpenServer = true
 	*utils.Cfg.ServiceSettings.EnableCommands = false