Add comments and update the span event from a test

tests/unit/test_pool.py

@@ -214,6 +214,7 @@ def test_get_non_expired(self):
             self.assertFalse(pool._sessions.full())
 
     def test_spans_bind_get(self):
+        # This tests retrieving 1 out of 4 sessions from the session pool.
         pool = self._make_one(size=4)
         database = _Database("name")
         SESSIONS = sorted([_Session(database) for i in range(0, 4)])
@@ -243,6 +244,7 @@ def test_spans_bind_get(self):
         self.assertSpanEvents("pool.Get", wantEventNames)
 
     def test_spans_bind_get_empty_pool(self):
+        # Tests trying to invoke pool.get() from an empty pool.
         pool = self._make_one(size=0)
         database = _Database("name")
         session1 = _Session(database)
@@ -270,6 +272,8 @@ def test_spans_bind_get_empty_pool(self):
         )
 
     def test_spans_pool_bind(self):
+        # Tests the exception generated from invoking pool.bind when
+        # you have an empty pool.
         pool = self._make_one(size=1)
         database = _Database("name")
         SESSIONS = []
@@ -458,7 +462,7 @@ def test_spans_get_empty_pool(self):
         wantEventNames = [
             "Acquiring session",
             "Waiting for a session to become available",
-            "No sessions available. Creating session",
+            "No sessions available in pool. Creating session",
         ]
         self.assertSpanEvents("pool.Get", wantEventNames)
 
@@ -477,6 +481,8 @@ def test_get_non_empty_session_exists(self):
         self.assertTrue(pool._sessions.empty())
 
     def test_spans_get_non_empty_session_exists(self):
+        # Tests the spans produces when you invoke pool.bind
+        # and then insert a session into the pool.
         pool = self._make_one()
         database = _Database("name")
         previous = _Session(database)
@@ -526,6 +532,7 @@ def test_put_empty(self):
         self.assertFalse(pool._sessions.empty())
 
     def test_spans_put_empty(self):
+        # Tests the spans produced when you put sessions into an empty pool.
         pool = self._make_one()
         database = _Database("name")
         pool.bind(database)
@@ -555,6 +562,8 @@ def test_put_full(self):
         self.assertIs(pool.get(), older)
 
     def test_spans_put_full(self):
+        # This scenario tests the spans produced from putting an older
+        # session into a pool that is already full.
         pool = self._make_one(target_size=1)
         database = _Database("name")
         pool.bind(database)
@@ -867,7 +876,9 @@ def test_ping_oldest_stale_and_not_exists(self):
         SESSIONS[1].create.assert_called()
         self.assertNoSpans()
 
-    def test_spans_get_empty_pool(self):
+    def test_spans_get_and_leave_empty_pool(self):
+        # This scenario tests the spans generated from pulling a span
+        # out the pool and leaving it empty.
         pool = self._make_one()
         database = _Database("name")
         session1 = _Session(database)