Add test for concurrent access on connection

test/integration/concurrency_test.py

@@ -0,0 +1,43 @@
+import pytest
+import pyexasol
+import threading
+from pyexasol import ExaConcurrencyError
+
+
+class QueryThread(threading.Thread):
+
+    def __init__(self, connection, timeout):
+        self.connection = connection
+        self.seconds = timeout
+        self.exception = None
+        super().__init__()
+
+    def run(self):
+        try:
+            # run heavy query
+            self.connection.execute(f'SELECT "$SLEEP"({self.seconds})')
+        except Exception as ex:
+            self.exception = ex
+
+    def join(self, timeout=None):
+        threading.Thread.join(self, timeout=timeout)
+        if self.exception:
+            raise self.exception
+
+
+@pytest.mark.exceptions
+def test_concurrency_error(dsn, user, password, schema):
+
+    # Note all timeouts and sleeps in this test case have been chosen by well-educated guesses
+    # TL;DR: Adjust timeouts if required/reasonable
+    query_time_in_seconds = 0.5
+
+    con = pyexasol.connect(dsn=dsn, user=user, password=password, schema=schema)
+    q1 = QueryThread(con, timeout=query_time_in_seconds)
+    q2 = QueryThread(con, timeout=query_time_in_seconds)
+
+    with pytest.raises(ExaConcurrencyError):
+        q1.start()
+        q2.start()
+        q1.join()
+        q2.join()