PresenceMap: only emit a leave if a member was present

per ably/specification#222

.mocharc.js

@@ -9,7 +9,7 @@ const config = {
 // if you've defined specs in your config. therefore we work around it by only adding specs to the
 // config if none are passed as arguments
 if (!process.argv.slice(2).some(isTestFile)) {
-  config.spec = ['test/realtime/*.test.js', 'test/rest/*.test.js'];
+  config.spec = ['test/realtime/*.test.js', 'test/rest/*.test.js', 'test/unit/*.test.js'];
 }
 
 function isTestFile(arg) {

src/common/lib/client/presencemap.ts

@@ -125,7 +125,7 @@ export class PresenceMap extends EventEmitter {
       delete map[key];
     }
 
-    return true;
+    return !!existingItem;
   }
 
   startSync() {

test/unit/presencemap.test.js

@@ -0,0 +1,48 @@
+'use strict';
+
+define(['chai', 'ably'], function (chai, Ably) {
+  const { assert } = chai;
+  const PresenceMap = Ably.Realtime._PresenceMap;
+
+  describe('PresenceMap', () => {
+    let presenceMap;
+
+    // Helper function to create a presence message
+    const createPresenceMessage = (clientId, connectionId, action, timestamp) => ({
+      clientId,
+      connectionId,
+      timestamp,
+      action,
+    });
+
+    beforeEach(() => {
+      // Initialize with a simple memberKey function that uses clientId as the key
+      presenceMap = new PresenceMap(
+        null,
+        (item) => item.clientId + ':' + item.connectionId,
+        (i, j) => i.timestamp > j.timestamp,
+      );
+    });
+
+    describe('remove()', () => {
+      it('should return false when no matching member present', () => {
+        const incoming = createPresenceMessage('client1', 'conn1', 'leave', 100);
+        assert.isFalse(presenceMap.remove(incoming));
+      });
+
+      it('should return true when removing an (older) matching member', () => {
+        const original = createPresenceMessage('client1', 'conn1', 'present', 100);
+        presenceMap.put(original);
+        const incoming = createPresenceMessage('client1', 'conn1', 'leave', 150);
+        assert.isTrue(presenceMap.remove(incoming));
+      });
+
+      it('should return false when trying to remove a newer matching member', () => {
+        const original = createPresenceMessage('client1', 'conn1', 'present', 100);
+        presenceMap.put(original);
+        const incoming = createPresenceMessage('client1', 'conn1', 'leave', 50);
+        assert.isFalse(presenceMap.remove(incoming));
+      });
+    });
+  });
+});