Add `runCommand` helper method to Neutrino.

packages/neutrino/src/neutrino.js

@@ -68,31 +68,22 @@ class Neutrino extends EventEmitter {
   }
 
   build(args) {
-    return this
-      .emitForAll('prebuild', args)
-      .then(() => this.builder())
-      .then(() => this.emitForAll('build', args));
+    return this.runCommand('build', args, () => this.builder());
   }
 
   start(args) {
-    return this
-      .emitForAll('prestart', args)
-      .then(() => {
-        const config = this.getWebpackOptions();
-
-        if (config.devServer) {
-          return this.devServer();
-        }
-
-        return this.watcher();
-      })
-      .then(() => this.emitForAll('start', args));
+    return this.runCommand('start', args, () => (this.getWebpackOptions().devServer ? this.devServer() : this.watcher()));
   }
 
   test(args) {
+    return this.runCommand('test', args);
+  }
+
+  runCommand(command, args = {}, fn) {
     return this
-      .emitForAll('pretest', args)
-      .then(() => this.emitForAll('test', args));
+      .emitForAll(`pre${command}`, args)
+      .then(fn)
+      .then(() => this.emitForAll(command, args));
   }
 
   devServer() {

packages/neutrino/test/api_test.js

@@ -94,6 +94,17 @@ test('import middleware for use', t => {
   t.notDeepEqual(api.getWebpackOptions(), {});
 });
 
+test('command emits events around execution', async (t) => {
+  const api = new Neutrino();
+  const events = [];
+
+  api.on('prebuild', () => events.push('alpha'));
+  api.on('build', () => events.push('gamma'));
+
+  await api.runCommand('build', {}, () => events.push('beta'));
+  t.deepEqual(events, ['alpha', 'beta', 'gamma']);
+});
+
 test('creates a Webpack config', t => {
   const api = new Neutrino();