Unit testing both Excel formulas and VB with the same tool? - vba

Question

Are there any tools that allow for unit testing both Excel formulas and Visual Basic forms within Excel? I'm finding methods that will do one or the other, but not both. Rubberduck for example looks promising for testing VBA, but does not appear to allow testing of formulas within Excel spreadsheets.

Answer 1

The only way I have found to "Unit Test" functions within Excel is to create a sheet within you workbook for which it's purpose in life is to be the validations page. Define Various additional functions within this sheet which look for edge cases and check additions etc within your workbook.
It is quite helpful to keep a comments field as well as a boolean success field that can be aggregated to put a custom format message on your other input pages to cue the user to a failed "Unit Test".
This approach can work quite well in making your testing reusable as well as transparent to the end users of your workbooks.

Answer 2

It is possible to unit test both Excel formulas and VBA using FlyingKoala. FlyingKoala is an extension of xlwings.
xlwings offers a COM wrapper which provides the ability to execute VBA from Python (by getting Excel to run it). It's a great library/solution. The esteemed Felix from ZoomerAnalyitics has written a blogpost about unit testing VBA using xlwings with examples.
FlyingKoala uses a library (xlcalculator) to convert Excel formulas into Python which can then be unit tested in Python's unittest framework. So it's possible to evaluate the formula and check against a known goal value whether that is in Excel or pre-defined.
An example of unit testing formulas using FlyingKoala while Excel is running;
import unittest
import logging
import xlwings as xw
from flyingkoala import FlyingKoala
from pandas import DataFrame
from pandas import Series
from numpy import array
from numpy.testing import assert_array_equal
from pandas.testing import assert_series_equal
logging.basicConfig(level=logging.ERROR)
class Test_equation_1(unittest.TestCase):
def setUp(self):
self.workbook_name = r'growing_degrees_day.xlsm'
if len(xw.apps) == 0:
raise "We need an Excel workbook open for this unit test."
self.my_fk = FlyingKoala(self.workbook_name, load_koala=True)
self.my_fk.reload_koala('')
self.equation_name = xw.Range('Equation_1')
if self.equation_name not in self.my_fk.koala_models.keys():
model = None
wb = xw.books[self.workbook_name]
wb.activate()
for name in wb.names:
self.my_fk.load_model(self.equation_name)
if self.equation_name == name.name:
model = xw.Range(self.equation_name)
self.my_fk.generate_model_graph(model)
if model is None:
return 'Model "%s" has not been loaded into cache, if named range exists check spelling.' % self.equation_name
def test_Equation_1(self):
"""First type of test for Equation_1"""
xw.books[self.workbook_name].sheets['Growing Degree Day'].activate()
goal = xw.books[self.workbook_name].sheets['Growing Degree Day'].range(xw.Range('D2'), xw.Range('D6')).options(array).value
tmin = xw.books[self.workbook_name].sheets['Growing Degree Day'].range(xw.Range('B2'), xw.Range('B6')).options(array).value
tmax = xw.books[self.workbook_name].sheets['Growing Degree Day'].range(xw.Range('C2'), xw.Range('C6')).options(array).value
inputs_for_DegreeDay = DataFrame({'T_min': tmin, 'T_max': tmax})
result = self.my_fk.evaluate_koala_model('Equation_1', inputs_for_DegreeDay).to_numpy()
assert_array_equal(goal, result)
def test_Equation_1_predefined_goal(self):
"""First type of test for Equation_1"""
goal = Series([0.0, 0.0, 0.0, 0.0, 0.0, 5, 10, 15, 20])
tmin = [-20, -15, -10, -5, 0, 5, 10, 15, 20]
tmax = [0, 5, 10, 15, 20, 25, 30, 35, 40]
inputs_for_DegreeDay = DataFrame({'T_min': tmin, 'T_max': tmax})
result = self.my_fk.evaluate_koala_model('Equation_1', inputs_for_DegreeDay)
assert_series_equal(goal, result)
def test_VBA_Equation_1(self):
"""
The function definition being called;
Function VBA_Equation_1(T_min As Double, T_max As Double) As Double
VBA_Equation_1 = Application.WorksheetFunction.Max(((T_max + T_min) / 2) - 10, 0)
End Function
"""
goal = 20
vba_equation_1 = xw.books[self.workbook_name].macro('VBA_Equation_1')
result = vba_equation_1(20.0, 40.0)
self.assertEqual(goal, result)