Heron unit testing

tests/unit_tests/README.md

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+# Unit Testing
+## HERON
+The `test_heron.py` file contains unit tests for the `FORCE/src/heron/create_componentsets_in_HERON()` function. These are designed to help developers identify bugs and isolate their causes. To this end, a brief overview of the most important unique scenarios each unit test addresses is listed below.
+
+### TestMinimalInput
+This test is designed to check main functionality with minimal edge cases. It checks that:
+- New Component node was added and updated with content, including:
+  - economics node
+  - capex CashFlow, with all attributes
+  - reference price
+  - reference driver, with conversion from kW to mW
+
+### TestExpandedInput1
+This test considers a more complex HERON input XML. It checks that:
+- Case node is transferred uncorrupted
+- Contents of multiple existing components that should not be updated are uncorrupted
+- New component's reference driver value is not converted if input is in mW
+- DataGenerators node is transferred uncorrupted
+
+### TestExpandedInput2
+This test focuses on ensuring correct updating of economics and CashFlow nodes and subnodes. It checks that:
+- Multiple components that need updating can be merged correctly with new components
+- Existing CashFlow of type non-capex is uncorrupted
+- capex CashFlow is added when a non-capex CashFlow exists but a capex CashFlow does not
+- economics node is found successfully when non-economics subnode of the component precedes the economics subnode
+- CashFlows are updated correctly when both a non-capex and a capex CashFlow exists
+- Non-CashFlow subnode of economics node is uncorrupted and CashFlow is still found
+- Existing capex CashFlow has
+  - Uncorrupted attributes
+  - Uncorrupted subnode that does not need updating
+  - All three existing subnodes that need updating correctly replaced
+- CashFlow subnodes are updated correctly when two of the three types that need updating exist
+
+### TestNoComponentsNode
+This test examines a single edge case where the Components node is missing from the HERON input XML script. It checks that:
+- A new Components node is created if one does not exist
+- The new Component node is placed within this new Components node
+
+### TestNoComponentNodes
+This test examines the edge case where a Components node exists, but no Component nodes. It checks that:
+- The new component is added, with content
+
+### TestMissingSubnodes
+This test considers scenarios where a component that needs to be updated is missing an economics or CashFlow subnode. It checks that:
+- If the economics node is missing, it is created with correct content
+- If the CashFlow node is missing, it is created with correct content
+
+### TestEmptyCompSetsFolder
+This test checks the function's behavior when the provided component set folder is empty. It checks that:
+- The open function was not called (e.g., no file was opened)
+- The existing component was not corrupted
+
+### TestCompSetsFolderWithBadJSON
+This test ensures a correct response to a component set file that is not is proper JSON format. It checks that:
+- The function throws a ValueError
+
+### TestCompSetsFolderMultFiles
+This test checks the function's filtering system regarding which component set files it should open. It checks that:
+- Only files whose names start with "componentSet" are opened
+- Only files of type .txt or .json are opened