a test using the "pyxform_v1_test_case" format, as in https://github.com/XLSForm/pyxform/pull/28

test_support_external_instances.py

from pyxform_test_case import PyxformTestCase

class TestSupportExternalInstances(PyxformTestCase):
    def test_csv_externals(self):
        # no choice filter
        self.assertPyxformXform(
            name="test_csv_externals",
            md="""
                #survey
                | type                               | name    | label            | choice_filter |
                | select_one_from_file countries.csv | country | Pick one country |               |
                """,
            model__contains=[
                '<instance id="cities" src="jr://file-csv/cities.csv" />',
                ],
            body__contains=[
                '''<itemset nodeset="instance('countries')/root/item">''',
                    '''<value ref="name" />''',
                    '''<label ref="label" />''',
                '''</itemset>'''
            ],
        )

    def test_xml_externals(self):
        # no choice filter
        self.assertPyxformXform(
            name="test_csv_externals",
            md="""
                #survey
                | type                               | name    | label            | choice_filter |
                | select_one_from_file countries.xml | country | Pick one country |               |
                """,
            model__contains=[
                '<instance id="cities" src="jr://file/cities.xml" />',
                ],
            body__contains=[
                '''<itemset nodeset="instance('countries')/root/item">''',
                    '''<value ref="name" />''',
                    '''<label ref="label" />''',
                '''</itemset>'''
            ],
        )

    def test_csv_externals_with_choice_filter(self):
        self.assertPyxformXform(
            name="test_csv_externals",
            md="""
                #survey
                | type                               | name    | label            | choice_filter        |
                | select_one_from_file countries.csv | country | Pick one country | country = ${country} |
                """,
            model__contains=[
                '<instance id="cities" src="jr://file-csv/cities.csv" />',
                ],
            body__contains=[
                '''<itemset nodeset="instance('cities')/root/item[country= /myform/country ]">''',
            ],
        )