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Tushar Pathak
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Illustration of Tushar writing in an open notebook at a wooden desk by a window — a green lamp, a cup of tea, stacked books, a plant, and a sketched flow diagram on loose paper.
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Essay 01

Green tests prove it runs. They don't prove it's right.

A note on why a fully green test suite still missed the defects that mattered.

2 min readRelated project: TeachSpark → (opens in a new tab)Draft — pending sign-off

“364 tests passed. Then I opened the actual file… Green tests prove it runs. They don't prove it's right.”
Source: TeachSpark — 9-Day Build Series (LinkedIn draft)
“The two most important defects this session… were both found by reading the code/reasoning, not by any test.”
Source: Cubicle — lesson-learnt.md

Draft — pending sign-off: this is a placeholder note, not the finished essay. It connects two separate build sessions — TeachSpark and Cubicle — around one recurring observation: a fully green test suite still let through the defects that turned out to matter most, and those were only caught by reading the code and the reasoning directly, not by any test passing or failing. The full essay, worked examples, and conclusion are not yet written.

Related project: TeachSpark → (opens in a new tab)