Nitpick: it would be more concise to do something like:
```python
expected_subs = [
    '00:00:00,200 --> 00:00:00,400\nsubs #1',
    '00:00:00,400 --> 00:00:00,480\nsubs #2',
    '00:00:00,480 --> 00:00:00,760\nsubs #3',
    '00:00:00,780 --> 00:00:02,000\nsubs #4',
    '00:01:48,000 --> 00:02:36,800\nsubs #5',
]
for sub in expected_subs:
    self.assertIn(sub, srt_subs)
```

Or, if you expect that list to be the exact content of the subs, and you don't care about the order:
```python
self.assertEqual(set(expected_subs), set(srt_subs))
```