topotest: add new run_and_expect variant

The new `run_and_expect` variant - called `run_and_expect_type` - tests
the return value type of the test function and optionally the return
value.

Now we can implement tests from test functions that return different
return types.

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>

tests/topotests/lib/test/test_run_and_expect.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python
+
+#
+# test_run_and_expect.py
+# Tests for library function: run_and_expect(_type)().
+#
+# Copyright (c) 2019 by
+# Network Device Education Foundation, Inc. ("NetDEF")
+#
+# Permission to use, copy, modify, and/or distribute this software
+# for any purpose with or without fee is hereby granted, provided
+# that the above copyright notice and this permission notice appear
+# in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND NETDEF DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NETDEF BE LIABLE FOR
+# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY
+# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+# OF THIS SOFTWARE.
+#
+
+"""
+Tests for the `run_and_expect(_type)()` functions.
+"""
+
+import os
+import sys
+import pytest
+
+# Save the Current Working Directory to find lib files.
+CWD = os.path.dirname(os.path.realpath(__file__))
+sys.path.append(os.path.join(CWD, '../../'))
+
+# pylint: disable=C0413
+from lib.topotest import run_and_expect_type
+
+def test_run_and_expect_type():
+    "Test basic `run_and_expect_type` functionality."
+
+    def return_true():
+        "Test function that returns `True`."
+        return True
+
+    # Test value success.
+    success, value = run_and_expect_type(return_true, bool, count=1, wait=0, avalue=True)
+    assert success is True
+    assert value is True
+
+    # Test value failure.
+    success, value = run_and_expect_type(return_true, bool, count=1, wait=0, avalue=False)
+    assert success is False
+    assert value is True
+
+    # Test type success.
+    success, value = run_and_expect_type(return_true, bool, count=1, wait=0)
+    assert success is True
+    assert value is True
+
+    # Test type failure.
+    success, value = run_and_expect_type(return_true, str, count=1, wait=0)
+    assert success is False
+    assert value is True
+
+    # Test type failure, return correct type.
+    success, value = run_and_expect_type(return_true, str, count=1, wait=0, avalue=True)
+    assert success is False
+    assert value is True
+
+
+if __name__ == '__main__':
+    sys.exit(pytest.main())

tests/topotests/lib/topotest.py

@@ -252,6 +252,54 @@ def run_and_expect(func, what, count=20, wait=3):
     return (False, result)
 
 
+def run_and_expect_type(func, etype, count=20, wait=3, avalue=None):
+    """
+    Run `func` and compare the result with `etype`. Do it for `count` times
+    waiting `wait` seconds between tries. By default it tries 20 times with
+    3 seconds delay between tries.
+
+    This function is used when you want to test the return type and,
+    optionally, the return value.
+
+    Returns (True, func-return) on success or
+    (False, func-return) on failure.
+    """
+    start_time = time.time()
+    func_name = "<unknown>"
+    if func.__class__ == functools.partial:
+        func_name = func.func.__name__
+    else:
+        func_name = func.__name__
+
+    logger.info(
+        "'{}' polling started (interval {} secs, maximum wait {} secs)".format(
+            func_name, wait, int(wait * count)))
+
+    while count > 0:
+        result = func()
+        if not isinstance(result, etype):
+            logger.debug("Expected result type '{}' got '{}' instead".format(etype, type(result)))
+            time.sleep(wait)
+            count -= 1
+            continue
+
+        if etype != type(None) and avalue != None and result != avalue:
+            logger.debug("Expected value '{}' got '{}' instead".format(avalue, result))
+            time.sleep(wait)
+            count -= 1
+            continue
+
+        end_time = time.time()
+        logger.info("'{}' succeeded after {:.2f} seconds".format(
+            func_name, end_time - start_time))
+        return (True, result)
+
+    end_time = time.time()
+    logger.error("'{}' failed after {:.2f} seconds".format(
+        func_name, end_time - start_time))
+    return (False, result)
+
+
 def int2dpid(dpid):
     "Converting Integer to DPID"