Unit Tests include "Ippl.h" and don't use mocks/stubs #399
Description
Issue 1: Unit test TUs include entire project
Description:
Each unit test file currently includes the full project headers (through including "Ippl.h"). This leads to:
- Slow rebuilds: each change to IPPL causes all unit tests to be recompiled.
- Unnecesary coupling: Tests depend on unrelated parts of the project.
Proposal:
Replace the inclusion of Ippl.h with a minimal set of headers required for the test
Benefits:
- Faster rebuilds.
- Clearer communication what the unit test is related to.
Issue 2: Unit tests don’t isolate components (no mocks/stubs)
Our current "unit" tests run against the full codebase; If we want to test something that interacts with an ippl::Field, we build against IPPL's actual implementation of a Mesh, FieldLayout, Field, partitioning strategy and (more subtly) IPPLs Comms object. This causes the following issues:
- Failures are more difficult to trace: If someone introduces a bug in
ippl::Field, it might only show up in a unit test related to interpolation. - Unclear contracts: Because components are always tested together, we aren’t forced to be precise about each component’s guarantees and interface. This makes components less modular and makes refactoring riskier.
Proposal:
- Introduce some helper code building mocks/stubs in order to facilitate the writing of unit tests in isolation.
- Keep current unit tests but treat them as integration tests.
- Reimplement them again using mocks/stubs.
Benefits:
- True "unit" tests that validate components in isolation.
- Clearer definition of each component’s guarantees and interfaces.
- Easier/safer refactoring.
- Faster to recompile and execute test-suite.