Add Test A Function With Pytest as a python til

README.md

@@ -9,7 +9,7 @@ and pairing with smart people at Hashrocket.
 
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@@ -520,6 +520,7 @@ _913 TILs and counting..._
 ### Python
 
 - [Access Instance Variables](python/access-instance-variables.md)
+- [Test A Function With Pytest](python/test-a-function-with-pytest.md)
 
 ### Rails
 

python/test-a-function-with-pytest.md

@@ -0,0 +1,33 @@
+# Test A Function With Pytest
+
+The [`pytest` framework](https://docs.pytest.org/en/latest/index.html) is a
+solid choice for unit testing your python project.
+
+Any file whose name is preceeded with `test_` that contains functions whose
+names are preceeded with `test_` will be processed and executed by the pytest
+test runner.
+
+```python
+# test_taco.py
+
+def taco(day):
+  return "Taco " + day
+
+def test_taco_tuesday():
+  assert taco("Tuesday") == "Taco Tuesday" # passes
+
+def test_taco_blank():
+  assert taco("") == "Taco" # fails, missing trailing space
+```
+
+Use `assert` statements to check that a comparison is `true`. If it isn't the
+`assert` statement will result in a test failure with some output about what
+went wrong.
+
+Ensure you have `pytest` installed and then run the following from your project
+directory:
+
+```bash
+$ pytest
+#=> ... you'll see the test output below
+```