Organize tests

test/browser/spec/ol/observable.test.js

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+import EventTarget from '../../../../src/ol/events/Target.js';
+import Observable, {unByKey} from '../../../../src/ol/Observable.js';
+
+describe('ol.Observable', function () {
+  describe('constructor', function () {
+    it('creates a new observable', function () {
+      const observable = new Observable();
+      expect(observable).to.be.a(Observable);
+      expect(observable).to.be.a(EventTarget);
+    });
+  });
+
+  describe('#on()', function () {
+    let observable, listener;
+    beforeEach(function () {
+      observable = new Observable();
+      listener = sinon.spy();
+    });
+
+    it('registers a listener for events of the given type', function () {
+      observable.on('foo', listener);
+
+      observable.dispatchEvent('foo');
+      expect(listener.calledOnce).to.be(true);
+
+      observable.dispatchEvent('foo');
+      expect(listener.callCount).to.be(2);
+    });
+
+    it('accepts an array of event types', function () {
+      observable.on(['foo', 'bar'], listener);
+
+      observable.dispatchEvent('foo');
+      expect(listener.calledOnce).to.be(true);
+
+      observable.dispatchEvent('bar');
+      expect(listener.callCount).to.be(2);
+    });
+
+    it('returns a listener key', function () {
+      const key = observable.on('foo', listener);
+
+      expect(typeof key).to.be('object');
+    });
+  });
+
+  describe('#once()', function () {
+    let observable, listener;
+    beforeEach(function () {
+      observable = new Observable();
+      listener = sinon.spy();
+    });
+
+    it('registers a listener that is only called once', function () {
+      observable.once('foo', listener);
+
+      observable.dispatchEvent('foo');
+      expect(listener.calledOnce).to.be(true);
+
+      observable.dispatchEvent('foo');
+      expect(listener.callCount).to.be(1);
+    });
+
+    it('is safe to dispatch events of same type in a once listener', function () {
+      let callCount = 0;
+      observable.once('change', function () {
+        observable.changed();
+        observable.changed();
+      });
+      observable.on('change', function () {
+        ++callCount;
+      });
+      expect(function () {
+        observable.changed();
+      }).to.not.throwException();
+      expect(callCount).to.be(3);
+    });
+
+    it('accepts an array of event types (called once for each)', function () {
+      observable.once(['foo', 'bar'], listener);
+
+      observable.dispatchEvent('foo');
+      expect(listener.calledOnce).to.be(true);
+
+      observable.dispatchEvent('foo');
+      expect(listener.callCount).to.be(1);
+
+      observable.dispatchEvent('bar');
+      expect(listener.callCount).to.be(2);
+
+      observable.dispatchEvent('bar');
+      expect(listener.callCount).to.be(2);
+    });
+
+    it('returns a listener key', function () {
+      const key = observable.once('foo', listener);
+
+      expect(typeof key).to.be('object');
+    });
+
+    it('can be unregistered with un()', function () {
+      observable.once('foo', listener);
+      observable.un('foo', listener);
+      observable.dispatchEvent('foo');
+      expect(listener.callCount).to.be(0);
+    });
+  });
+
+  describe('#un()', function () {
+    let observable, listener;
+    beforeEach(function () {
+      observable = new Observable();
+      listener = sinon.spy();
+    });
+
+    it('unregisters a previously registered listener', function () {
+      observable.on('foo', listener);
+
+      observable.dispatchEvent('foo');
+      expect(listener.calledOnce).to.be(true);
+
+      observable.un('foo', listener);
+      observable.dispatchEvent('foo');
+      expect(listener.calledOnce).to.be(true);
+    });
+  });
+
+  describe('ol.Observable.unByKey()', function () {
+    let observable, listener;
+    beforeEach(function () {
+      observable = new Observable();
+      listener = sinon.spy();
+    });
+
+    it('unregisters a listener given the key returned by `on`', function () {
+      const key = observable.on('foo', listener);
+
+      observable.dispatchEvent('foo');
+      expect(listener.calledOnce).to.be(true);
+
+      unByKey(key);
+      observable.dispatchEvent('foo');
+      expect(listener.callCount).to.be(1);
+    });
+  });
+});