fix the skip event calculation (#242)

test/machine.test.ts

@@ -6,14 +6,43 @@ import { EventType } from '../src/types';
 const events = sampleEvents.filter(
   (e) => ![EventType.DomContentLoaded, EventType.Load].includes(e.type),
 );
+const nextEvents = events.map((e) => ({
+  ...e,
+  timestamp: e.timestamp + 1000,
+}));
+const nextNextEvents = nextEvents.map((e) => ({
+  ...e,
+  timestamp: e.timestamp + 1000,
+}));
 
 describe('get last session', () => {
   it('will return all the events when there is only one session', () => {
-    expect(getLastSession(events)).to.deep.equal(events);
+    expect(getLastSession(events, events[0].timestamp)).to.deep.equal(events);
   });
 
   it('will return last session when there is more than one in the events', () => {
-    const multiple = events.concat(events).concat(events);
-    expect(getLastSession(multiple)).to.deep.equal(events);
+    const multiple = events.concat(nextEvents).concat(nextNextEvents);
+    expect(
+      getLastSession(
+        multiple,
+        nextNextEvents[nextNextEvents.length - 1].timestamp,
+      ),
+    ).to.deep.equal(nextNextEvents);
+  });
+
+  it('will return last session when baseline time is future time', () => {
+    const multiple = events.concat(nextEvents).concat(nextNextEvents);
+    expect(
+      getLastSession(
+        multiple,
+        nextNextEvents[nextNextEvents.length - 1].timestamp + 1000,
+      ),
+    ).to.deep.equal(nextNextEvents);
+  });
+
+  it('will return first session when baseline time is previous time', () => {
+    expect(getLastSession(events, events[0].timestamp - 1000)).to.deep.equal(
+      events,
+    );
   });
 });