chore: make async CLI branches testable

karma-runner · johnjbarton · Mar 23, 2021 · Feb 28, 2021 · Feb 28, 2021 · Mar 2, 2021
commit 3038717aea6266f6bdd1c7ffd949d49944ab5b13
diff --git a/lib/cli.js b/lib/cli.js
@@ -282,28 +282,33 @@ exports.run = () => {
   const cliOptions = exports.process()
   const cmd = cliOptions.cmd // prevent config from changing the command
   const cmdNeedsConfig = cmd === 'start' || cmd === 'run' || cmd === 'stop'
+  let runPromise
   if (cmdNeedsConfig) {
-    cfg.parseConfig(
+    runPromise = cfg.parseConfig(
       cliOptions.configFile,
       cliOptions,
       {
         promiseConfig: true,
         throwErrors: true
       }
     ).then(function onKarmaConfigFulfilled (config) {
+      let fulfillmentValue
       switch (cmd) {
-        case 'start':
-          new Server(config).start()
+        case 'start': {
+          const server = new Server(config)
+          fulfillmentValue = server.start().then(() => server)
           break
+        }
         case 'run':
-          require('./runner')
+          fulfillmentValue = require('./runner')
             .run(config)
             .on('progress', printRunnerProgress)
           break
         case 'stop':
-          require('./stopper').stop(config)
+          fulfillmentValue = require('./stopper').stop(config)
           break
       }
+      return fulfillmentValue
     }, function onKarmaConfigRejected (/* ignoredReason */) {
       // The reject reason isn't used to log a message since parseConfig already
       // calls a configured logger method with an almost identical message.
@@ -313,15 +318,26 @@ exports.run = () => {
       process.exit(1)
     })
   } else {
-    switch (cmd) {
-      case 'init':
-        require('./init').init(cliOptions)
-        break
-      case 'completion':
-        require('./completion').completion(cliOptions)
-        break
+    try {
+      let fulfillmentValue
+      switch (cmd) {
+        case 'init':
+          fulfillmentValue = require('./init').init(cliOptions)
+          break
+        case 'completion':
+          fulfillmentValue = require('./completion').completion(cliOptions)
+          break
+      }
+      runPromise = Promise.resolve(fulfillmentValue)
+    } catch (ex) {
+      runPromise = Promise.reject(ex)
     }
   }
+
+  // Always return a promise for ease of testing. We want to know when it is
+  // safe to start making assertions. Without the promise, it would be difficult
+  // to test the asynchronous branches.
+  return runPromise
 }
 
 // just for testing