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Do not re-invent the wheel. Every homegrown mock, test tool or framework needs to itself be tested and maintained. There are tons of good testing frameworks and tools out there, use those instead.
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Write Clean and Re-Usable Test Code
Maintain testing code as you would production code. This means keep the test code clean and extract re-usable code when it makes sense to do so.
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A Lot of Repeated Test Code
See Best Practices, Smells and Anti-Patterns.Write Clean And Re-Usable Test Code
Creating Mocks Manually
See
Test Multiple Behaviors in a Single Test
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