test: add test for halfOpen state allowing only one fire()

Refs: #119

test/common.js

@@ -33,6 +33,17 @@ function timedFunction (ms) {
   });
 }
 
+function timedFailingFunction (ms) {
+  return new Promise((resolve, reject) => {
+    const timer = setTimeout(() => {
+      reject(`Failed after ${ms}`);
+    }, ms);
+    if (typeof timer.unref === 'function') {
+      timer.unref();
+    }
+  });
+}
+
 function nonPromise () {
   return 'foo';
 }
@@ -49,6 +60,7 @@ module.exports = exports = {
   passFail,
   slowFunction,
   timedFunction,
+  timedFailingFunction,
   callbackFunction,
   failedCallbackFunction,
   nonPromise

test/half-open-test.js

@@ -0,0 +1,42 @@
+'use strict';
+
+const test = require('tape');
+const opossum = require('../');
+const { timedFailingFunction } = require('./common');
+
+test('When half-open, the circuit only allows one request through', t => {
+  t.plan(12);
+  const options = {
+    errorThresholdPercentage: 1,
+    resetTimeout: 500
+  };
+
+  const breaker = opossum(timedFailingFunction, options);
+  breaker.fire(1)
+    .catch((e) => t.equals(e, 'Failed after 1'))
+    .then(() => {
+      t.ok(breaker.opened, 'breaker should be open');
+      t.notOk(breaker.pendingClose, 'breaker should not be pending close');
+    })
+    .then(() => {
+      setTimeout(() => {
+        t.ok(breaker.halfOpen, 'breaker should be halfOpen');
+        t.ok(breaker.pendingClose, 'breaker should be pending close');
+        breaker
+          .fire(500) // fail after a long time, letting possibly other fire()s to occur
+          .catch((e) => t.equals(e, 'Failed after 500', 'function should fail again'))
+          .then(() => {
+            t.ok(breaker.opened, 'breaker should be open again');
+            t.notOk(breaker.halfOpen, 'breaker should not be halfOpen');
+            t.notOk(breaker.pendingClose, 'breaker should not be pending close');
+          });
+      }, options.resetTimeout * 1.1);
+    });
+  // fire the breaker again, and be sure it fails as expected
+  breaker.fire(1)
+    .catch((e) => t.equals(e, 'Failed after 1'))
+    .then(() => {
+      t.ok(breaker.opened, 'breaker should be open');
+      t.notOk(breaker.pendingClose, 'breaker should not be pending close');
+    });
+});