test: implementing basic tests and validating the workflow

pytest.ini

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+[pytest]
+pythonpath = "src"
+

tests/requirements.txt

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+# tests
+pytest~=8.3.4
+pytest-cov~=6.0.0
+# linting
+#flake8 
+

tests/test_input_handling.py

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+import pytest
+
+from input_handling import is_valid_email
+
+# generate tests for is_valid_email
+# - test with valid email
+#    - basic email with @ and .
+#    - test with email with multiple .
+# - test with empty email
+# - test with None email
+# - test with non-string email
+# - test with invalid email
+#    - test with email without @
+#    - test with email without .
+#    - test with email without domain
+#    - test with email without username
+#    - test with email without TLD
+#    - test with email with multiple @
+#    - test with email starting with the + sign
+
+
+def test_is_valid_email_valid():
+    assert is_valid_email("[email protected]")
+    assert is_valid_email("[email protected]")
+    assert is_valid_email("[email protected]")
+    assert is_valid_email("[email protected]")
+    assert is_valid_email("[email protected]")
+    
+def test_is_valid_email_empty():
+    assert not is_valid_email("")
+    
+def test_is_valid_email_none():
+    with pytest.raises(TypeError):
+        is_valid_email(None)
+    
+def test_is_valid_email_non_string():
+    with pytest.raises(TypeError):
+        is_valid_email(123)
+        
+    
+def test_is_valid_email_invalid():
+    assert not is_valid_email("a.bc")
+    assert not is_valid_email("a@bc")
+    assert not is_valid_email("a.b@cc")
+    assert not is_valid_email("@b.cc")
+    assert not is_valid_email("[email protected]")
+    assert not is_valid_email("a@b.")
+    assert not is_valid_email("a@bb.")
+    assert not is_valid_email("[email protected].")
+    assert not is_valid_email("a@[email protected]")
+
+# not sure how xfails come through the CI pipeline yet.
+# maybe better to just comment out this stuff until pipeline is setup, then can check /extend
+#@pytest.mark.xfail(reason="Bug identified, but while setting up CI having failing tests causes more headache")
+#def test_is_valid_email_invalid_plus():
+#    assert not is_valid_email("[email protected]")
+#    assert not is_valid_email("[email protected]")