Fixing the api_streams sensor (#22200)

* Fire events with websocket messages.

* Added tests to validate

* Fixed api_streams sensor to use new sensor

* Delete from coverageac as now works.

* Removed websocket request event.

* Use dispatcher instead of events.

* Moved sensor to under websocket_api

* Changes as per code review

* Fixed tests.

* Modified test

* Patch

tests/components/websocket_api/test_sensor.py

@@ -0,0 +1,30 @@
+"""Test cases for the API stream sensor."""
+
+from homeassistant.bootstrap import async_setup_component
+
+from tests.common import assert_setup_component
+from .test_auth import test_auth_via_msg
+
+
+async def test_websocket_api(hass, no_auth_websocket_client, legacy_auth):
+    """Test API streams."""
+    with assert_setup_component(1):
+        await async_setup_component(hass, 'sensor', {
+            'sensor': {
+                'platform': 'websocket_api',
+            }
+        })
+
+    state = hass.states.get('sensor.connected_clients')
+    assert state.state == '0'
+
+    await test_auth_via_msg(no_auth_websocket_client, legacy_auth)
+
+    state = hass.states.get('sensor.connected_clients')
+    assert state.state == '1'
+
+    await no_auth_websocket_client.close()
+    await hass.async_block_till_done()
+
+    state = hass.states.get('sensor.connected_clients')
+    assert state.state == '0'