adding code_testing section

code_testing/1_code_testing.md

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+## Code Testing
+
+One of the most important factors for a scientific code is being correct.
+We want to be able to check that the code is giving the answer we expect and that any changes to the code are not inadvertantly changing the output.
+This is why tests are a part of high quality code.
+
+# Types of Tests
+
+Unit tests are small tests that each test a particullar part (or unit) of the code.
+Unit tests are used to test each function one at a time, and in some cases might even test just part of a function or class.
+
+Integration tests check that pieces of code are working together as expected.
+This is used for multiple functions at the same time.
+
+Regression tests look at the final answer for an example input and are used to check that changes to one part of the code are not changing the overall performance.
+
+# Code Coverage
+
+Code coverage is a metric related to how much of your code is being tested.
+Low code coverage suggests that there are parts of the code that may or may not contain bugs.
+In this case, writting more tests is recommended.
+
+High code coverage is good, but does not guarentee that all bugs have been found.
+Some functions might need more than one test to cover all the possible input cases.

code_testing/1_pytest.md

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+## Pytest
+
+Pytest is one example of a program used for running tests.
+The documentation for pytest can be found [here](https://docs.pytest.org)
+
+*Activity* Change to the code_testing directory of the software workshop.
+Look at the functions.py code and the test_functions.py.
+Try running the test. Does it pass? if not why not and can you fix the code so that the test passes?
+Does the test cover all the functionality? Try writting more tests.

code_testing/functions.py

@@ -1,8 +1,15 @@
 import numpy as nmp
 
-def frequency_calculation(lamdas, temp):
+def frequency_calculation(lamda):
+    """
+    Calculate the frequency based on the equation
+    frequency = 1/(2pi) * sqrt(x)
+    """
     pi = nmp.pi
-    kt = 4.11e-21 * temp / 298
-    frequencies = 1/(2*pi) * nmp.sqrt(lamdas/kt)
+
+    # calculate the frequency
+    frequency = 1/(pi) * nmp.sqrt(lamda)
+
+    return frequency
+
 
-    return frequencies

code_testing/test_functions.py

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+from code_testing import functions as fun
+
+def test_frequency_zero():
+    lamda = 0
+
+    assert fun.frequency_calculation(lamda) == 0
+
+def test_frequency_int():
+    lamda = 2
+
+    assert fun.frequency_calculation(lamda) == 0.22507907903927654
+