test(spec): SafeEventEmitter

Author: sambacha

src/events/spec.test.ts

@@ -0,0 +1,84 @@
+/**
+* @test SafeEventEmitter
+* @spec expect
+*/
+
+import SafeEventEmitter from '.';
+
+describe('SafeEventEmitter', () => {
+  it('can be constructed without error', () => {
+    expect(new SafeEventEmitter()).toBeDefined();
+  });
+
+  it('can emit a value with no listeners', () => {
+    const see = new SafeEventEmitter();
+    expect(see.emit('foo', 42)).toBe(false);
+  });
+
+  it('can emit a value with 1 listeners', () => {
+    expect.assertions(2);
+
+    const see = new SafeEventEmitter();
+    see.on('foo', (x) => expect(x).toBe(42));
+    expect(see.emit('foo', 42)).toBe(true);
+  });
+
+  it('can emit a value with 2 listeners', () => {
+    expect.assertions(3);
+
+    const see = new SafeEventEmitter();
+    see.on('foo', (x) => expect(x).toBe(42));
+    see.on('foo', (x) => expect(x).toBe(42));
+    expect(see.emit('foo', 42)).toBe(true);
+  });
+
+  it('returns false when _events is somehow undefined', () => {
+    const see = new SafeEventEmitter();
+    see.on('foo', () => { /* */ });
+    delete (see as any)._events;
+    expect(see.emit('foo', 42)).toBe(false);
+  });
+
+  it('throws error from handler after setTimeout', () => {
+    jest.useFakeTimers();
+    const see = new SafeEventEmitter();
+    see.on('boom', () => {
+      throw new Error('foo');
+    });
+    expect(() => {
+      see.emit('boom');
+    }).not.toThrow();
+    expect(() => {
+      jest.runAllTimers();
+    }).toThrow('foo');
+  });
+
+  it('throws error emitted when there is no error handler', () => {
+    const see = new SafeEventEmitter();
+    expect(() => {
+      see.emit('error', new Error('foo'));
+    }).toThrow('foo');
+  });
+
+  it('throws error emitted when there is no error handler AND _events is somehow undefined', () => {
+    const see = new SafeEventEmitter();
+    delete (see as any)._events;
+    expect(() => {
+      see.emit('error', new Error('foo'));
+    }).toThrow('foo');
+  });
+
+  it('throws default error when there is no error handler and error event emitted', () => {
+    const see = new SafeEventEmitter();
+    expect(() => {
+      see.emit('error');
+    }).toThrow('Unhandled error.');
+  });
+
+  it('throws error when there is no error handler and error event emitted', () => {
+    const see = new SafeEventEmitter();
+    expect(() => {
+      see.emit('error', { message: 'foo' });
+    }).toThrow('Unhandled error. (foo)');
+  });
+});