Design for testing starts with the failures you need to detect. Inspection, bare-board electrical test, in-circuit test and functional test answer different questions. Combine them around the product risks and build volume, then reserve the physical and software access each method needs.
Write a coverage matrix
List representative defects such as opens, shorts, missing parts, wrong values, reversed components and programming errors. For each, identify the proposed detection method and its limitations. Do not treat a test name as a coverage guarantee; the fixture, program and accessible nodes determine what is actually checked.
Design usable physical access
Agree probe style, pad size, spacing, side access and fixture support with the test provider. Keep tall components, coating and mechanical obstructions in the review. Mark intentional no-probe regions and identify alternate access for important nodes that cannot be reached directly.
Define the functional test state
Specify supplies, loads, firmware, configuration, interfaces and pass/fail limits. Include setup, settling time and safe shutdown. A technician should not have to infer what a passing waveform looks like from an undocumented engineering prototype.
Make results traceable
Associate each result with the board identifier, hardware revision, firmware version, test-program revision and relevant fixture calibration. Decide how retest and repair history will be recorded. A final pass without the earlier failure context can conceal an intermittent issue.
Example: a regulator output test
Measuring the unloaded output confirms only one operating point. A fuller test may check startup, representative load, input variation and an agreed transient response. Select the cases that cover the product requirements, state the measurement method and preserve the limits with the test revision.
Design review checklist
- Map important failure modes to actual test coverage.
- Approve access and fixture support before routing is frozen.
- Provide firmware, limits and test sequence together.
- Define serialization, retest and repair records.