Test coverage measures how much of a codebase is tested by automated tests. In technical due diligence, it serves as a proxy for engineering discipline, product stability, and risk exposure—especially during scaling or post-acquisition transitions.

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Test coverage is a quantitative metric that indicates the percentage of code exercised by automated tests. It helps teams understand how thoroughly their software is tested—and where the blind spots are.

Types of test coverage include:

• Line coverage: Proportion of source lines executed by tests
• Branch coverage: Coverage of all logical branches in conditionals
• Path coverage: All possible code execution paths (rare in practice)
• Function/method coverage: Whether each method is tested at least once

While 100% coverage is rarely necessary—or realistic—low test coverage often points to fragile or risky systems.

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Test coverage is a key indicator in Tech DD because it reflects both product reliability and engineering maturity:

• Reduces production risk: More coverage = fewer regressions and bugs
• Accelerates integration: New teams or owners can deploy safely with confidence
• Improves maintainability: Well-tested code can be refactored without fear
• Signals DevOps discipline: Suggests CI/CD and QA processes are in place
• Supports roadmap feasibility: Features built on tested code are more likely to ship on time

During audits, poor or missing test coverage often signals hidden technical debt or cultural misalignment in engineering.

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