Initial Commit

test/observables/Subject.test.ts

@@ -0,0 +1,55 @@
+import {jest, describe, it, expect} from 'bun:test';
+import {Subject} from '../../src/observables';
+
+describe('A Subject', () => {
+  it('exposes the Subject value', () => {
+    const subject = new Subject<string>('init-value');
+
+    expect(subject.value).toBe('init-value');
+  });
+
+  it('updates the Subject value when set', () => {
+    const subject = new Subject<string>('init-value');
+
+    subject.value = 'some thing';
+
+    expect(subject.value).toBe('some thing');
+  });
+
+  it('notifies subcribers when subscribing', () => {
+    const subject = new Subject<string>('init-value');
+    const listener = jest.fn() as (value: string) => void;
+
+    subject.subscribe(listener);
+
+    expect(listener).toHaveBeenCalledWith('init-value');
+  });
+
+  it('notifies subcribers when value changes', () => {
+    const subject = new Subject<string>('init-value');
+    const listener = jest.fn() as (value: string) => void;
+
+    subject.subscribe(listener);
+
+    subject.value = 'some thing';
+
+    expect(listener).toHaveBeenCalledWith('some thing');
+  });
+
+  it('notifies all subcribers when value changes', () => {
+    const subject = new Subject<string>('init-value');
+    const listener1 = jest.fn() as (value: string) => void;
+    const listener2 = jest.fn() as (value: string) => void;
+    const listener3 = jest.fn() as (value: string) => void;
+
+    subject.subscribe(listener1);
+    subject.subscribe(listener2);
+    subject.subscribe(listener3);
+
+    subject.value = 'some thing';
+
+    expect(listener1).toHaveBeenCalledWith('some thing');
+    expect(listener2).toHaveBeenCalledWith('some thing');
+    expect(listener3).toHaveBeenCalledWith('some thing');
+  });
+});