TypeError on empty action

.eslintrc

@@ -10,7 +10,7 @@
     "arrow-parens": ["error", "as-needed"],
     "arrow-body-style": ["error", "as-needed"],
     "prefer-template": "error",
-    "max-len": ["warn", { "code": 80 }],
+    "max-len": ["warn", { "code": 80, "ignoreStrings": true }],
     "no-unused-vars": ["warn", {
       "argsIgnorePattern": "^_$|^e$|^reject$|^resolve$"
     }],

lib/circuit.js

@@ -110,7 +110,7 @@ class CircuitBreaker extends EventEmitter {
     return !!error[OUR_ERROR];
   }
 
-  constructor (action = {}, options = {}) {
+  constructor (action, options = {}) {
     super();
     this.options = options;
     this.options.timeout =
@@ -128,6 +128,13 @@ class CircuitBreaker extends EventEmitter {
 
     this.semaphore = new Semaphore(this.options.capacity);
 
+    // check if action is defined
+    if (!action) {
+      throw new TypeError(
+        'No action provided. Cannot construct a CircuitBreaker without an invocable action.'
+      );
+    }
+
     this[VOLUME_THRESHOLD] = Number.isInteger(options.volumeThreshold)
       ? options.volumeThreshold : 0;
     this[WARMING_UP] = options.allowWarmUp === true;

test/test.js

@@ -971,6 +971,16 @@ test('CircuitBreaker without a timeout', t => {
     .catch(t.fail);
 });
 
+test('CircuitBreaker without an action', t => {
+  t.plan(1);
+  try {
+    // eslint-disable-next-line
+    const _ = new CircuitBreaker();
+  } catch (err) {
+    if (err instanceof TypeError) t.pass();
+  }
+});
+
 const noop = _ => {};
 const common = require('./common');
 const identity = common.identity;